Polyacrylonitrile (PAN) fiber is the most widely used carbon fiber precursor, and methyl acrylate (MA) copolymer is widely used for research and commercial purposes. The properties of P (AN-MA) fibers improve increasingly as the molecular weight increases, but high-molecular-weight materials have some limitations with respect to the manufacturing process. In this study, P (AN-MA) precursor fibers of different molecular weights were prepared and analyzed to identify an efficient carbon fiber precursor manufacturing process. The effects of the molecular weight of P (AN-MA) on its crystallinity and void structure were examined, and precursor fiber content and process optimizations with respect to molecular weight were conducted. The mechanical properties of high-molecular-weight P (AN-MA) were good, but the internal structure of the high-molecular-weight material was not the best because of differences in molecular entanglement and mobility. The structural advantages of a relatively low molecular weight were confirmed. The findings of this study can help in the manufacturing of precursor fibers and carbon fibers with improved properties. Polyacrylonitrile (PAN) fiber has been the most widely used precursor in carbon fiber manufacturing since the 1970s ,3. PAN hP (AN-MA) copolymer is typically manufactured with 3–6 wt.% MA. The processability typically improves with increasing MA, but the mechanical properties are adversely affected; therefore, an MA content higher than 6 wt.% is not recommended . The limIn this study, to investigate P (AN-MA) behavior under drawing conditions, the changes that occur in the mechanical behavior and properties of P (AN-MA) copolymer with changes in molecular weight were analyzed from a microstructural perspective. The PAN copolymer used for fiber spinning was polymerized to obtain various molecular weights, and the molecular weight and composition of the polymerized P (AN-MA) material were confirmed through gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) analysis to confirm the characteristics of the polymerized material. The polymerized material was spun and drawn through a wet-spinning process and a dry stretching process, respectively. Changes in the physical properties before and after stretching with changes in the molecular weight of the manufactured fibers were verified. Through image analysis, it was confirmed that there were no singularities before or after the stretching of each fiber and other factors affecting the mechanical properties. In addition, the crystallinity and void structure of each fiber was analyzed by x-ray diffraction (XRD) analysis. The effects of changes in the molecular weight of P (AN-MA) fibers manufactured by the same process on the microstructure of carbon fibers were examined, and microstructural differences in fibers with different molecular weights were investigated.The PAN copolymer was polymerized by the typically used basic solution polymerization process ,23. The P (AN-MA) precursor fibers were manufactured through spinning, washing, and stretching processes. A dope solution with a concentration of 25 wt% was prepared and spun, as suggested in previous fiber spinning research ,22. DMSO1H NMR  analysis was performed by integrating the signal ranges of the H protons of methine (CH), methylene (CH2), and methyl (CH3) contained in the copolymer. The relative numbers of hydrogens appearing in each peak were compared, and the following formula (Equation (1)) was developed. The molar ratio was calculated according to the molecular weight of the P(AN-co-MA) polymer, measured using Waters GPC  to determine the weighted average molecular weight (Mw) and the polymer distribution index (PDI). To confirm that the polymer was suitable for use as a spinning solution at high concentrations, P (AN-MA) polymers with different molecular weights were prepared at 25 wt%, and the viscosity was measured using a rotary rheometer  at room temperature  and shear rates  polymer, 400-MHz The surface structure of the fibers was observed using an electron microscope , and the spinning and fiber dimensions were confirmed through the images. Chemical bonds and residual solvents in the polymers were examined by Fourier-transform infrared spectroscopy . The microstructure of the fiber was measured through wide-angle X-ray diffraction (WAXD)  and small-angle X-ray scattering (SAXS)  with a radiation wavelength of 0.154 nm (Cu Kα). Measurement of microstructures in fibers through WAXD and SAXS has been conducted in previous studies ,25. In p1H NMR and GPC analyses of the compositions and molecular weights of the P (AN-MA) polymers prepared by solution polymerization. The Mw of 150 k (LPAN) and 300 k (HPAN) were higher at 191 k and 337 k, respectively, and the Mw of 250 k (MPAN) was lower with a Mw of 221 k. However, all PDI polymers were uniformly polymerized to within 2, and the difference in molecular weight was distinct, which is believed to have affected the mechanical properties of the P (AN-MA) polymer and fiber depending on the molecular weight. To check whether wet spinning was possible when preparing a spinning solution with a high concentration of P (AN-MA) polymer, the viscosity of the spinning solution prepared at 25 wt% was measured at shear rates of 0.01–900 1/s at RT. At a shear rate of 1/s, the viscosity according to molecular weight was measured to be 19.09 Pa·s for LPAN, 94.45 Pa·s for MPAN, and 188.29 Pa·s for HPAN. It can be seen in To assess the effects of differences in the molecular weight of P (AN-MA) polymers on the surface shape during precursor fiber formation, the surfaces of as-spun and six-time drawn fibers of P (AN-MA) precursor fibers with different molecular weights were observed with an electron microscope (SEM). The results are shown in 2 vibration near 2940 and 2840 cm−1, C≡N (AN) near 2240 cm−1, C=O stretching (MA) near 1730 cm−1, CH2 deformation near 1450 cm−1, and C-O stretching around 1060 cm−1 were observed. The main difference between the drawn fiber and the undrawn fiber was that O-H (H2O) was observed only in the as-spun fiber at 3630 cm−1. The reason that this was not observed in the drawn fiber is that the moisture contained in the pores of the fiber was reduced in size, and the moisture evaporated in the process of hot drawing.Changes in the functional groups before and after the drawing of P (AN-MA) precursor fibers with different molecular weights were analyzed using an FT-IR spectrometer  and are The microstructural changes according to the molecular weight and stretching behavior of P(AN-co-MA) precursor fibers were analyzed through WAXD and SAXS. The microstructure within the fiber can be largely divided into polymer crystal, amorphous material, and void space. Since crystallinity and amorphous regions are microscales, they are measured by WAXD. Additionally, void space is nanoscale and, therefore, is measured by SAXS. Through WAXD analysis, the crystallinity and crystal size of fibers, which are important factors that determine the mechanical properties of fibers, can be calculated. The results of the analysis are shown in Thus, crystal size can be calculated using Equation (3), where K is a constant with a value of 0.89, the wavelength (λ) used in the device is 0.154 nm, and β is the full width at half maximum (FWHM) of the strong peak .s (where s is the scattering vector) in 2D SAXS  on the mechanical properties of precursor fibers was measured using a single-fiber tensile strength tester, and the results are shown in In this study, P (AN-MA) copolymers with different molecular weights were solution-polymerized, precursor fibers were prepared through a wet-spinning process, and the properties and microstructures of the fibers were analyzed according to drawing. The molecular weights of the homogeneously polymerized P (AN-MA) copolymers were confirmed through NMR and GPC analyses. The P (AN-MA) precursor fibers exhibited differences in surface shape and properties depending on the molecular weight. In addition, the molecular structure and microstructure of the precursor fibers were analyzed according to the drawing behavior. Although molecular weight did not significantly affect crystallinity and crystal size, according to WAXD analysis, the crystal size was affected by drawing and the molecular weight. In addition, the molecular weight of the copolymer increased, as determined by SAXS analysis, and the size of the voids increased as a result of interference with the diffusion of the solvent in the fiber. As WAXD showed, the sizes and shapes of the voids could be controlled through the spinning and drawing process. In conclusion, it is possible to control the mechanical properties and microstructure of PAN-based precursor fibers by controlling the molecular weight and drawing conditions during their manufacture. The findings of this study can help in the manufacturing of precursor fibers and carbon fibers with improved properties.


Background and Objectives: Percutaneous mitral valve repair using a MitraClip system is an established therapeutic strategy to treat severe mitral regurgitation, which is recommended by guidelines in Europe and in the United States, whereas residual mitral regurgitation is associated with mortality and morbidity. Accurate assessment of residual mitral regurgitation is crucial for risk stratification and further adequate intervention, whereas its quantification has technical limitations due to “double” regurgitation that is often encountered following valve clipping. Remote dielectric sensing (ReDSTM) is a non-invasive electromagnetic-based technology to quantify lung fluid levels and might be a promising tool to assess the impact of residual mitral regurgitation following MitraClip. Materials and Methods: Following MitraClip, ReDS values measurements and right heart catheterization were performed and correlated. Results: We had 13 patients  who underwent successful MitraClip. According to the visual estimation, eight patients had none or mild regurgitation, and five patients had moderate regurgitation. ReDS values were distributed widely between 16% and 33%, irrespective of the severity of regurgitation. ReDS values had a moderate correlation with invasively measured pulmonary artery wedge pressure . Conclusions: ReDS value might be a promising tool to assess residual pulmonary congestion following MitraClip, irrespective of the visually estimated severity of residual mitral regurgitation. Functional severe mitral regurgitation is associated with mortality and morbidity in patients with chronic heart failure. Percutaneous edge-to-edge mitral valve repair using MitraClip system  has recently been introduced with favorable post-procedural clinical outcomes . HoweverTransthoracic echocardiography is an established tool to quantify the degree of mitral regurgitation. However, accurate quantification of residual mitral regurgitation following MitraClip is challenging due to a “double” regurgitant jet, which is often encountered due to iatrogenic partial mitral valve approximating . FollowiTM, Sensible Medical Innovations Ltd., Netanya, Israel) is a recently introduced electromagnetic-based technology, which quantifies lung fluid levels  transthoracic echocardiography, as well as (2) ReDS measurements, as detailed below, and (3) invasive right heart catheterization. ReDS values were blinded to the examiners of other tests. The institutional ethical review board approved the protocol, and all participants signed informed consent.Two-dimensional and Doppler echocardiography was performed and standard echocardiography data, including visual assessment of residual mitral regurgitation following MitraClip procedures, were obtained by the board-certified cardiologists. The severity of mitral regurgitation was graded as none, trace, mild, moderate, moderate to severe, and severe . QuantifReDS values were measured at a sitting position under normal breathing as detailed previously  5]. ReD. ReD5]. Invasive right heart catheterization was performed by board-certified cardiologists and standard hemodynamics data, including pulmonary artery wedge pressure (PAWP), were obtained according to the standard manner. All procedures were performed via jugular venous access. All intra-cardiac data were obtained at an end-expiratory timing. All the procedures were supervised and obtained data were reviewed by the senior heart failure specialist.p values less than 0.05 were considered significant.Continuous variables are presented as median and interquartile ranges (IQRs). Categorical variables are presented as numbers and percentages. Association between ReDS values and PAWP was assessed by Pearson’s correlation coefficient. Trends in ReDS values before and after MitraClip procedure was assessed using Wilcoxon signed-rank test. All calculations were performed in SPSS Statistics 23.0 software , and two-sided A total of 13 patients underwent successful MitraClip for advanced mitral regurgitation . The medFollowing MitraClip, median left ventricular end-diastolic diameter was 55  mm and median left ventricular ejection fraction was 45% . According to the visual estimation, eight (62%) patients had none or mild residual mitral regurgitation, and five (38%) patients had moderate mitral regurgitation. Median PAWP was 13  mmHg and median plasma B-type natriuretic peptide was 163  pg/mL. ReDS values were distributed widely between 16% and 33% with a median value of 28%.p = 0.004; ReDS values and PAWP had a moderate correlation  on median, which decreased significantly following MitraClip (In this proof-of-concept preliminary study, we demonstrated that ReDS values had a moderate correlation with invasively measured PAWP in patients following MitraClip, irrespective of the visually estimated severity of residual mitral regurgitation. Of note, some patients had relatively higher ReDS values despite visually estimated none or mild mitral regurgitation. ReDS values decreased following MitraClip in most of the patients, except for three patients.MitraClip is an established therapeutic tool to treat severe mitral regurgitation , whereasReDS system has been demonstrated to be mildly or moderately correlated with other modalities, including high-resolution computed tomography ,9 and inOur institute performed invasive right heart catheterization prior to index discharge following MitraClip during a specific study period, but it is not routinely performed in all institutes, as it is an invasive procedure and requires the appropriate resources. ReDS might be a promising alternative to invasive right heart catheterization to assess the impact of residual mitral regurgitation upon pulmonary congestion following MitraClip. As we observed, pulmonary congestion would decrease following MitraClip (black bars in Of note, the impact of residual mitral regurgitation might be sometimes underestimated by visual assessment alone. Even visually estimated mild mitral regurgitation might be associated with persistently elevated ReDS values, as we observed.Thus, we highly recommend ReDS measurements for all candidates of MitraClip, irrespective of the visually estimated severity of residual mitral regurgitation. Further studies are warranted to validate the clinical implication of ReDS-guided management of residual pulmonary congestion following MitraClip.This is a proof-of-concept preliminary study consisting of a small sample size that limited statistical implication. ReDS has been approved to be commercially available in Japan in June 2022, and further multi-center larger-scale studies are warranted to validate our findings. Moreover, the pharmacoeconomic and feasibility of utilizing ReDS for daily practice in standard institutes, by accounting for the cost of this device, should be validated. The association of ReDS values with other modalities among those receiving MitraClip remains unknown. ReDS values and PAWP were not extremely high and their association among those with decompensated heart failure following MitraClip procedure remains unknown. The prognostic impact of pulmonary congestion due to residual mitral regurgitation, which was indirectly assessed by ReDS technology in this study, remains a topic needing further investigation.ReDS system might be a promising tool to assess the impact of residual mitral regurgitation upon pulmonary congestion in patients receiving MitraClip beyond the visual estimation of the severity of residual mitral regurgitation.


Antimicrobial resistance (AMR) has been clearly identified as a major global health challenge. It is a leading cause of human deaths and also has a toll on animals, plants, and the environment. Despite the considerable socio-economic impacts, the level of awareness of the problem remains woefully inadequate, and antimicrobials are not generally recognized as a global common good, one that everyone has a role and responsibility to conserve. It is imperative for antimicrobial stewardship to be more widely implemented to achieve better control of the AMR phenomenon. The Food and Agriculture Organization (FAO) of the United Nations plays an important role in promoting and facilitating antimicrobial stewardship. The specific needs to be addressed and barriers to be overcome, in particular, in low- and middle-income countries in order to implement antimicrobial stewardship practices in agrifood systems are being identified. As a global community, it is essential that we now move beyond discussing the AMR problem and focus on implementing solutions. Thus, FAO provides multi-pronged support for nations to improve antimicrobial stewardship through programs to strengthen governance, increase awareness, develop and enhance AMR surveillance, and implement best practices related to antimicrobial resistance in agrifood systems. For example, FAO is developing a platform to collect data on AMR in animals and antimicrobial use (AMU) in plants (InFARM), working on a campaign to reduce the need to use antimicrobials, studying the use of alternatives to the use of antimicrobials  and actively promoting the implementation of the Codex Alimentarius AMR standards. Together, these will contribute to the control of AMR and also bring us closer to the achievement of multiple sustainable development goals. Antimicrobials are naturally occurring semi-synthetic or synthetic substances that kill or inhibit the replication of microorganisms. Remarkable achievements have been reached in human medicine due to the availability and efficacy of antimicrobials, from the treatment of previously fatal infections to surgical procedures, otherwise impossible. In parallel, the use of antimicrobials in animals  and plant production and protection have also contributed to increased animal health and welfare, agricultural outputs, and, overall, food safety and security and the economic wellbeing of millions of agricultural producers and livestock keepers across the globe. Antimicrobial resistance (AMR) can be defined as the inherited or acquired characteristic of microorganisms to survive or proliferate in concentrations of an antimicrobial that would otherwise kill or inhibit them. In practical terms, the view of AMR is often simplistic and narrow, referring only to the failure of antibiotics to treat human patients. The true dimensions of this problem are, however, much broader. Although all antibiotics are antimicrobials, not all antimicrobials are antibiotics. The term antimicrobial encompasses a much larger group of agents with diverse targets, including some heavy metals, some antiparasitic drugs, fungicides, and biocides. Moreover, antimicrobials are not only used in humans but also in many aquatic and terrestrial animals  and crop/plant production and protection. Many of the same antimicrobial classes are used in humans and animals, and a few of these are also used in plants. The transfer of resistance genes among bacteria present in humans, animals, plants, and the environment underscores the need for antimicrobial stewardship in all domains, including in human health, agrifood systems, and the environment. The common use of antimicrobials in animal and plant production systems has raised concerns for the individuals using and applying these compounds in agrifood production systems, the safety of food, and environmental contamination with both antimicrobials and antimicrobial-resistant microorganisms, which are challenging to quantify and trace, and complicate mitigation strategies. These concerns are not limited to the use of antibiotics but also the use of some heavy metals and fungicides. For example, the use of triazole fungicides for protecting crops has contributed to anti-fungal resistance in the pathogen responsible for the human disease aspergillosis .Antimicrobial resistance threatens the attainment of many of the 2030 Sustainable Development Goals (SDGs). Recent modeling work on the global impact of AMR estimated that antimicrobial-resistant infections directly caused 1.27 million deaths in 2019 and played an indirect role  in 4.95 million deaths, placing AMR as a leading cause of human deaths worldwide [The solution to AMR will unfortunately not be the development of new antimicrobials. Very few novel antimicrobial classes have been discovered and commercialized since the late 1980s. The process of drug development and approval is long and resource intensive. Moreover, resistance is also predicted to develop against any newly developed antimicrobial. Thus, the need to preserve the efficacy of the classes of antimicrobial that are currently available is imperative.Because AMR knows no species, sector, or geographic borders, and some antimicrobials are used across humans, animals, and plants/crops, it represents a perfect example of a challenge that could benefit greatly from a One Health approach on a global scale. The definition of “One Health”, according to the One Health High-Level Expert Panel (OHHLEP), is “an integrated, unifying approach that aims to sustainably balance and optimize the health of people, animals, and ecosystems. It recognizes that the health of humans, domestic and wild animals, plants, and the wider environment (including ecosystems) are closely linked and inter-dependent. The approach mobilizes multiple sectors, disciplines, and communities at varying levels of society to work together to foster well-being and tackle threats to health and ecosystems while addressing the collective need for clean water, energy, and air, safe and nutritious food, taking action on climate change, and contributing to sustainable development”.In 2015, a global action plan on AMR was among the first attempts to coordinate global action on AMR . SubsequThe purpose of this paper is to describe some of the main initiatives that FAO has engaged in to promote and enable antimicrobial stewardship (AMS), as outlined in the FAO Action Plan on AMR (2021–2025) , includiPromoting and supporting antimicrobial stewardship (AMS) at the global, national, and local levels is dependent on building strong supporting pillars. From the FAO perspective, these pillars are (1) awareness, (2) governance, (3) practices, and (4) surveillance. The following looks at some of the key elements of these pillars and some of the tools and resources available to build them .Despite the alarming numbers of human deaths, the awareness of the AMR phenomenon is still limited for most lay people. The terminology used in this field can be frequently misinterpreted, with a common confusion between “the body” being resistant vs. the actual microorganism being resistant to the antimicrobial used . Even inLeverage participatory approaches to better understand stakeholder perspectives and motivations;Identify barriers to change and pilot collaborative solutions for a science-based approach to interventions; andEnable, empower, and incentivize stakeholders to transform knowledge and awareness of AMR risks into action.From an agrifood perspective on the global scale, the most recent FAO Action Plan on AMR (2021–2025)  highlighThe following sub-sections look globally at FAO efforts to raise awareness and examine barriers to change and participatory actions that can help identify and overcome them.To more effectively raise awareness and transform it into action, the objective and target audience for awareness raising must be clear. At a global level, FAO leverages and synergizes its organizational strengths by partnering with other organizations and entities to keep AMR on the global agenda in an ongoing effort to secure ongoing high-level commitment to address this challenge. An example of one recent initiative, in collaboration with Johns Hopkins University/React, introduces AMR/AMU into strategic policy venues where these issues might be taken up for discussion by key stakeholder groups, from government officials to civil society.Providing access to knowledge is also critical so that those advising policymakers and politicians have up-to-date information that will inform the brief of those partaking in international dialogues. In addition to publishing data, FAO started a monthly Knowledge Dissemination Dialogue webinar series as a means of making experts and knowledge more accessible to all countries. These data-rich webinars bring participants up to date on specific scientific and technical topics related to AMR. These may include, among others, microbiology, epidemiology, environmental or behavioral science, plant and animal production, and health. They are open, free of charge, and available on the FAO YouTube channel  and provSocial media and communication channels that can be widely and easily accessed through cell phone technology are key in order to reach wider audiences. Thus providing context-specific information on AMR and simple messages and actions for different sectors through different social media channels are increasingly gaining traction.Strengthening the FAO AMR website as it relates to plant health;Developing factsheets, policy briefs, and guidance documents on the use of antibiotics and fungicides in plant agriculture;Organizing information webinars and workshops for FAO member countries on AMR and AMU in the plant health sector to improve farmer’s knowledge of AMR and AMU in plant production and protection and on alternatives to minimize the use of pesticides that contain antimicrobial substances by reviewing extension material and implementing Farmer Field School Programs focusing on, for example, integrated pest management (IPM), biological control and the use of disease-resistant crop varieties. These webinars and workshops are good opportunities to clarify, for example, that in some countries, antibiotics are classified as pesticides, and farmers might be using them without being properly aware of this fact;Improving farmer knowledge on AMR and AMU in plant production and protection and on alternatives to minimize the use of pesticides that contain antimicrobial substances by reviewing extension material and implementing Farmer Field School Programs focusing on, for example, integrated pest management (IPM), biological control and the use of disease-resistant crop varieties.To increase awareness raising, communication, and advocacy among the plant production and protection sectors, the following initiatives are ongoing:The related work plan will be implemented through a coordinated, multisectoral, One Health approach that is key to addressing AMR in the context of the 2030 Agenda for Sustainable Development and in support of the FAO Action Plan on AMR 2021–2025.AMR can be considered a social problem, thereby requiring social solutions . ConsequTo begin understanding these influencers and drivers, the FAO has been exploiting the power of mixed-methods qualitative and quantitative approaches to identify the knowledge, attitudes, and practices that drive AMR, including patterns of antimicrobial use and practices for on-farm infection prevention and control. This “bottom-up approach” emphasizes that interventions and strategies to address AMR must be evidence-based and should draw upon knowledge, attitudes, and practices displayed by a wide range of stakeholders with the power to affect AMR in the agrifood sector, including farmers, animal health professionals, agrifood producers, policymakers and citizens .The benefits to AMR of this bottom-up approach are exemplified by an international study supported by the Fleming Fund of the United Kingdom. Broadly, this study assessed patterns of knowledge, attitudes, and practices among users, sellers, and prescribers of antimicrobials within livestock systems across five sub-Saharan African countries, including Ghana, Kenya, Tanzania, Zambia, and Zimbabwe . On a tyResults from the studies such as the ones described above highlight several important challenges to addressing AMR within low- and middle-income countries and in the animal health sector. First, across countries and livestock production systems, a person’s knowledge and attitude toward AMR did not predict their AMR-relevant practices ,10. ThatTo address these barriers, the FAO has begun implementing AMR Farmer Field School (FFS) programs in selected countries. In a typical FFS, a group of farmers (15–20) meets on a weekly basis at a demonstration farm over the course of a production cycle . The school proceeds under the guidance of a trained FFS facilitator, who is often a local animal health or agricultural extension worker. FFS are well suited to addressing the knowledge-practice gap as the approach is based on the principles of adult-centered learning  and the exchange and creation of knowledge through group-level problem solving. In addition, while the schools themselves cannot address resource constraints in the animal health sector, they can provide an opportunity for farmers to work with their local animal health professionals to develop trust and thus maximize the capacities available. A recent evaluation study comparing participants in layer poultry farming FFS in Kenya and Ghana to non-FFS participants shows that FFS participants reported more prudent practices, including reducing and even eliminating the use of antimicrobials in layer production. In addition, FFS participants reported greater investments in biosecurity and were more likely to call an animal health professional upon the first sign of disease in their flocks .Governance is an essential component of global, national, regional, and local responses to AMR. In this section, “AMR governance” refers to the diffuse and collaborative processes and systems through which a range of public and private actors and entities articulate their interests, frame and prioritize issues, and make, implement, monitor, and enforce AMR-related decisions. There is a broad consensus that AMR governance must adopt a One Health approach . BecauseThe United Nations General Assembly (UNGA) Resolutions in December 2015  and SeptIn 2018, FAO, WOAH, and WHO signed a Memorandum of Understanding (MoU) regarding cooperation to combat health risks at the animal/human/ecosystems interface, in the context of the “One Health” approach and including antimicrobial resistance. In 2022, UNEP signed the MoU, making it quadripartite. The new quadripartite MoU provides a legal and formal framework for the four organizations to tackle the challenges at the human, animal, plant, and ecosystem interface using a more integrated and coordinated approach. The quadripartite has, among other initiatives, developed a joint strategy on AMR, which includes as part of its outcomes the support to countries to develop policy and legislative effective and country-owned AMR responses.Two key dimensions of AMR governance at the national level are discussed here. The first involves the coordination of AMR national policies through a multidisciplinary entity. The second entails the strengthening of regulatory  frameworks that are relevant for AMR. Many national action plans (NAPs)  display A national-level coordinating mechanism must bring together all stakeholders, including government ministries, parliamentarians, civil society organizations, the private sector, academia, and regional and international partners. Such a coordinating body should have a clear mandate or terms of reference (which may include overseeing the implementation of the AMR policy), an established budget, a defined accountability framework, and should integrate actions and interventions vertically within a sector or horizontally across sectors . AccordiThe second element of AMR governance at the national level involves the alignment of sector-specific national policies and legislation with relevant international standards , such asAs noted above, good governance is also supported through the availability of internationally recognized standards that support AMR governance at the national level. FAO, together with WHO, is a parent organization of the Codex Alimentarius Commission, an intergovernmental body responsible for establishing food safety and quality standards that protect consumers and facilitate fair practices in the food trade. Codex has recently completed work in updating and developing new standards to support the management and containment of foodborne AMR . Over a During their development, the international standards adopted by the Codex Alimentarius Commission brought countries from around the world together to recognize and discuss the challenges posed by AMR in the food chain and the actions that need to be taken by all countries to manage and contain the problem. Getting agreement on all aspects of the new and revised Codex texts was challenging and required years of discussion and negotiation, further challenged with all interactions being moved to the virtual domain due to COVID. There were many bridges to build, and the importance of addressing an issue as significant as AMR in a One Health manner encouraged countries to build those bridges. This good will reared means there is now an opportunity to seek the engagement and support of countries to implement what was agreed in the Codex standards: developing surveillance programs, taking a risk-based approach, addressing AMR along the food chain, and adhering to agreed principles on the responsible and prudent use of antimicrobials to name but a few. The Republic of Korea is leading the way here, supporting FAO with a five-year project to implement the Codex standards on AMR. This project focuses in particular on developing monitoring and surveillance programs and implementing measures to minimize and contain foodborne AMR. Working with pilot countries in Asia and Latin America that are in different stages of their national AMR response planning and implementation, the project will enable FAO to gain practical experience in implementing these Codex standards, which can then be shared to help drive and facilitate their implementation elsewhere and support a somewhat harmonized approach to the management and containment of AMR along the food chain.The establishment of an enabling environment for change through awareness raising, education, financing, monitoring, and appropriate governance contributes to the ability of individuals, organizations, and nations to address the problem of antimicrobial resistance. However, until such time that behaviors  change, there will be limited progress on reducing and mitigating the agricultural contributions of AMR.Fundamental to antimicrobial stewardship in the agrifood sectors is limiting the use of antimicrobials. Reducing the use of antimicrobials when they are not needed or when they are used improperly is the first step in antimicrobial use . Stewardship may lead to the maintenance of the efficacy of the drugs as well as an economic savings for producers. Consultation of health professionals and access to appropriate diagnostics is critical for appropriate use. FAO has developed a number of tools and guidelines for raising animals  healthily with decreased use of antimicrobials.In addition to using antimicrobials responsibly, a large number of practices can be employed to reduce the future need for antimicrobials in plant and animal production.In plant production, FAO has provided some suggestions on how to reduce the need for antimicrobials in plant production, specifically through the use of integrated pest management (IPM) practices . AdditioApplying good husbandry practices while handling the animals, in the animal production establishments, and during animal transport;Improving animal welfare  during all phases, including production, transport, and slaughter;Using animals of locally adapted breeds that are more resistant to diseases and stress or animals bred for disease resistance ;Ensuring good hygiene, biosecurity measures, and general conditions on farms and during animal transport; these practices prevent the transmission of AMR;Applying rigorous disease control measures , antibiotics are frequently used to treat bacterial infections that are secondary to many diseases that are preventable by vaccination. Preventing these diseases reduces the need for antimicrobials;Applying good practices for waste management.A wide range of animal production practices contributes to increasing animal wellbeing and making them more resistant and resilient to diseases, therefore minimizing the need to use antimicrobials. Some examples:In addition, functional animal nutrition to promote animal health is one of the most powerful tools available to decrease the need for antimicrobials in animal production. Nutrition affects the critical functions required for host defense and disease resistance. Animal nutrition strategies should therefore aim to support these host defense systems and reduce the risk of the presence in feed and water of potentially harmful substances, such as mycotoxins, antinutritional factors  and pathogenic bacteria and other microbes.General dietary measures to promote gastrointestinal tract health include the selective use of a combination of feed additives and feed ingredients to stabilize the intestinal microbiota and support mucosal barrier function.Good nutrition allows the expression of the genetic potential of animals for different traits, including resistance to disease or stress, growth, milk or egg production, and reproductive functions. These depend on the availability of sufficient  feed resources around the year, the genetic makeup of the animals, climatic and disease conditions, and husbandry practices.Livestock nutrition programs are supported by diverse classes of feed additives, which have already been developed, marketed, and used in daily practice. Many of these functional additives are based on traditional fermentation techniques  and preservation technologies (organic acids). Other feed additives, such as phytochemicals, have their roots in traditional health practices and ethno-veterinary medicine. Evaluating locally available feed ingredients and traditional remedies based on herbal products abundantly available in the local environment should be integrated into the feeding strategy to reduce the need for the use of antimicrobials in livestock production.Ensuring drinking water quality. The consumption of water of appropriate quality is a prerequisite for animal health. Regular control of the quality, supply and accessibility of water, and regular sanitation of water storage and delivery systems using disinfecting agents, are important measures to keep animals healthy. However, this could prove a challenge in regions with water shortages or high levels of water pollution;Ensuring feed safety and quality. Measures to ensure feed safety and quality include: minimizing the presence of microbiological, chemical, and physical hazards; ensuring appropriate levels of available protein, energy, and other nutrients and micronutrients to meet the requirements of the animal and ensure productivity, and ensuring appropriate physical characteristics such as particle size and pellet durability and hardness. Risk management in relation to the safety of feed and feed ingredients is an essential part of good feed production and manufacturing practices;Precision feeding. Knowledge of the nutritional requirements of species and breeds, and their specific needs at different life phases, has advanced feeding regimes, furthering sustainable production levels over the entire lifespan. Milestones in advancing feeding practices include the increasing availability and use of high-quality proteins, vitamins, chelated minerals, feed preservatives, and enzymes such as phytases, which all improve feed utilization. While these practices are proven to be effective at the producer level, their success partly depends on the safety and quality of feed and feed ingredients, which vary in nutrient and digestible energy content. In many countries, the availability of feed and feed ingredients of sufficient quality at every time of the year is an increasing concern. Agricultural practices, feed processing (mixing and pelleting), and the level of education of animal nutritionists and producers are key determinants of successful animal nutrition programs.Good nutrition also supports the critical functions required for a healthy gastrointestinal tract, host defense, and health. Various feeding practices can be used to reduce the presence of potentially harmful contaminants  and antinutritional factors in feed and water. Such practices include:Feed additives. These are intentionally added ingredients not normally consumed as feed by themselves, whether or not they have nutritional value, which affects the characteristics of feed or livestock products. Diverse classes of feed additives have been developed, marketed, and used in livestock practices. The total market value was estimated at USD 38 billion in 2021 and was expected to reach USD 50 billion by 2026. These comprise prebiotics, probiotics, synbiotics, organic acids, and phytogenic compounds. A wide range of feed additives can be recommended to foster gastrointestinal and overall health, even under physiological or environmental stressful conditions such as weaning and regrouping, heat stress, undesirable antinutritional factors, and contaminants such as toxins. Such feed additives are promoted based on their effect on gut health, thereby improving feed utilization, the gut-associated immune system, and resilience to infectious diseases. While AGPs aim to stabilize the intestinal microbiota, a similar result can be achieved with non-antimicrobial compounds, which balance the microbiome and stimulate digestive enzymes and nutrient transport across a functional intestinal barrier. An improvement of intestinal health directly results in an improvement of the immune competence of an animal and hence overall resilience against infectious diseases. Improving gut health increases feed efficiency and, in turn, growth rate and productivity over the entire lifespan in all livestock species. Therefore, feed additives can not only replace AGP use in the improvement of gut health and immune competence but can also gradually reduce the need for antimicrobials for veterinary medical purposes. However, the efficacy and consistency of many feed additives can vary and are affected by feed composition, animal health and welfare, management practices, and the physical and social environment. FAO has already issued publications providing detailed information on relevant good practices, for example, the FAO/IFIF manual of Good Practices for the Feed Sector , the FAOSurveillance and research are essential to guide stakeholder decisions on how best to slow the emergence and spread of AMR for the good of food security and the health of humans, plants, animals, and the environment, globally. Strong surveillance and monitoring programs collect risk-based epidemiological and microbiological data on AMR, AMU, and antimicrobial residues relevant to each agriculture sub-sector and specific value chain that can be integrated with surveillance in humans and the environment. In general, surveillance for tracking antimicrobial resistance among bacteria and fungi recovered from human specimens is far more advanced than those for isolates from sick and healthy animals, from plants, food, and the environment, especially in low- and middle-income countries.This information then allows for timely assessment of hazards to feed risk assessments to develop appropriate interventions and monitor their effectiveness over time for minimizing and containing AMR. Reliable data are needed on antimicrobial-resistant microorganisms—their distribution, AMR profiles, and prevalence—in addition to data on the extent of antimicrobial use (AMU) and antimicrobial residues along the food and feed chains, as well as through the various environments impacted by terrestrial  agriculture and aquaculture.Escherichia coli, Campylobacter spp., nontyphoidal Salmonella spp., and Staphylococcus aureus) found in livestock. The study also shows AMR hotspots in several parts of the world [Harmonized data to estimate AMR levels in the food and agriculture sectors are still scarce. A recent study shows an increasing trend for antimicrobial resistance in common indicator pathogens  needs to be strengthened. Over the past few years, different initiatives worldwide have focused on and supported the generation of AMR surveillance data from the food and agriculture sectors, especially in LMICs. For this purpose, the FAO has developed and deployed a diagnostic instrument, the Assessment Tool for Laboratories and AMR Surveillance Systems (FAO-ATLASS), that assesses and defines targets to improve national AMR surveillance systems in the food and agriculture sectors. This tool has been used successfully used in more than 45 countries and 170 laboratories to date. More specifically, FAO-ATLASS is composed of two modules: the surveillance module and the laboratory module. Each module includes two standardized questionnaires that are completed by trained assessors in collaboration with the country representatives. Outputs of the assessment help countries identify limitations and gaps in their surveillance systems and assist them in the prioritization of investment and the development of roadmaps for surveillance strengthening.One of the key elements critical to strengthening country capacities for surveillance and monitoring of AMR and AMU in food and agriculture is to ensure countries employ standardized approaches to collecting, analyzing, interpreting, and sharing data. However, often, as identified by ATLASS assessments, data are often not analyzed or used to inform decisions. Frequently reported reasons for this disconnect in data collection and use are the lack of adequate data management systems, unclear definition of roles and responsibilities in data reporting, and the dearth of trained personnel able to perform analysis and interpretation. FAO plans to continue supporting members in building and consolidating laboratory and surveillance capacity to generate, collect, and analyze high-quality data within national surveillance systems across all food and agriculture sectors.The FAO has long-standing experience developing and providing hosting data platforms to members for safe data storage and tools for data analysis and interpretation. FAO’s role as a neutral, impartial, independent, and specialized agency of the United Nations places the organization in the best position to establish a hosting data platform to support members for storing, analyzing, and using their own AMR data generated at a national level from the food and agriculture sectors.FAO is committed to developing the building blocks that will catalyze national efforts to regularly generate and analyze reliable and comparable AMR data in food and agriculture and AMU data in plants and crops. With this purpose in mind, FAO started to develop a prototype for the International FAO Antimicrobial Resistance Monitoring (InFARM) IT platform in early 2022. FAO will be working with an initial set of countries to participate in developing and testing this data platform prototype during 2022. Countries will be involved in activities for pilot testing using their own data.The development of InFARM will follow a progressive approach. The initial scope of the prototype of the InFARM IT platform will be to host AMR data in priority bacterial species of interest for public health, animal health, and indicator bacteria from animals and food, according to international standards and recommendations from Codex Alimentarius guidelines for integrated monitoring and surveillance of foodborne AMR and animal health codes of the World Organization for Animal Health . Global rollout of the InFARM IT platform and expansion to additional functionalities and surveillance priorities under FAO’s remit, such as data on the use of antimicrobial pesticides in plants, are planned upon completing the pilot phase, as baseline data and the capacity to monitor AMR and AMU in the plant health sector are lacking.The InFARM IT platform will build momentum for enabling national surveillance, facilitating the process of data analysis, integration, and national reporting, and sustaining the monitoring of the country’s progress in actions against AMR in food and agriculture. This momentum is envisioned to further support the expansion of the InFARM platform as a wider system to support national surveillance activities such as formalization and establishment of national surveillance networks; capacity building of national focal points and experts on data generation and sharing; and adaptation of data management solutions and the interoperability with laboratory information management systems.To support countries in collecting, analyzing, and using their AMR data from animals and food for national purposes. InFARM will support capacity building for global harmonization of AMR data generated by laboratory-based surveillance and will serve as a one-stop source of relevant contextual information on AMR and AMU surveillance programs and linked activities ;E. coli in animals) to measure the impact of actions to minimize and contain AMR in food and agriculture sectors at the global level.To support countries willing to publicly share AMR data from food and agriculture sectors for global surveillance as a public common good for international advocacy and action to tackle AMR. InFARM will include support for sharing data  into the global tripartite integrated system for surveillance of AMR/AMU (TISSA). Public information on AMR prev-alence from InFARM will be the data source for outcome indicators included in the Monitoring & Evaluation (M&E) framework of the global action plan on AMR   report recommendation to ‘establish a constituency-based partnership platform to develop and work towards a shared global vision, goals and coordinated action on AMR’ and given the need to leverage local and sectoral knowledge on AMR and engage a wide variety of stakeholders from the public and private sectors, to generate and sustain systemic change, the quadripartite  put in place a multi-stakeholder partnership platform on AMR as part of the AMR global governance along with the GLG and IPEA.The platform aims to be an inclusive, international, and multi-stakeholder forum, which brings together relevant actors across the human, animal, plant, and environment interface to assist in preserving antimicrobials as lifesaving medicines and ensuring their responsible use under a One Health approach. It promotes a shared global vision, builds consensus, and takes targeted action to address the growing global threat of AMR through a coordinated, multisectoral, inclusive One Health approach to contribute to the achievement of the 2030 Agenda for Sustainable Development, universal health coverage, and strengthening of health systems for future pandemic prevention and preparedness.Given that the multisectoral work on AMR requires engagement from health, agriculture, environmental, pharmaceutical, trade, finance, and other sectors, the multi-stakeholder dimension of the platform enables deliberate coordination and collaboration within and between these sectors and stakeholders. It allows stakeholders such as governments, UN organizations and their specialized bodies, regional and intergovernmental organizations, civil society, research and academia institutions, private sector companies, philanthropic organizations, and multilateral organizations to make their voices heard, share their expertise, knowledge, and lessons learned, align positions, and catalyze actions to tackle AMR at community, national, regional, and global level.Improved dialogue, coordination, and collective public engagement on AMR targeting sectors, disciplines, and levels within countries and territories, as well as with quadripartite, AMR governance structures ) and other relevant stakeholders such as UN agencies, multilateral organizations, resource partners;Better common understanding of the AMR challenges and opportunities at community, country, regional and global levels for efficient and evidence-based decision making and action;Sustainable and effective actions to tackle AMR through One Health operationalization at community, country, regional and global levels;Emerging innovative public-private partnerships and alliances contributing to building the economic case of AMR, promoting the global public health research agenda, etc.;Heightened awareness, political uptake, and stakeholder ownership to tackle AMR through a One Health approach.The expected outcomes of the platform include:Currently, there are many ongoing AMR activities across the globe, yet as the COVID-19 pandemic highlighted, siloed approaches and initiatives focusing on specific aspects of health without looking through holistic One Health lenses may jeopardize global AMR containment efforts. The platform can potentially be an instrument to break these silos at all levels by operationalizing the One Health approach for AMR and creating an enabling environment for strengthened coordination, dialogue, and joint efforts to advance the delivery of the GAP, NAPs, and 2030 agenda and its SDGs. The platform’s geographical coverage is global, but a special focus is on LMICs and underrepresented stakeholders.Agrifood systems are facing all-time challenges as the global food demand is rapidly rising, estimated to increase by 35–56% between 2010 and 2050 . This reAntimicrobials are a precious discovery; their use has allowed saving millions of lives and providing food at levels that were impossible before. However, we have reached a point where its use in our current agrifood production systems, while providing positive outcomes, is also compromising that same use. It is for that reason that the call to reduce the need for antimicrobials is becoming clearer than ever. The Global Leaders Group on AMR in August 2021 released the following statement: “Applying a One Health approach, there is a critical need to transform food systems to optimize animal, plant, and environmental health, ensure responsible and sustainable antimicrobial use, and most importantly, reduce the need to use antimicrobials and promote innovation for evidence-based and sustainable alternatives” .The FAO Committee on Agriculture (COAG) subcommittee on livestock has recommended requesting FAO collect scientific evidence on alternative feeding practices to replace the use of medically important antimicrobials used as growth promoters (AGPs), their effectiveness and safety, and to develop an inventory of these practices and disseminate related knowledge. The subcommittee has also recommended sharing successful experiences and good practices, including traditional knowledge, to support members in reducing the need for antimicrobials.A “Reduce the need” initiative would, therefore, greatly benefit from an FAO’s unique comparative advantage as a multisectoral and multidisciplinary organization with solid internal institutional architecture and has been working actively in many countries around the world supporting national One Health platforms.The control of the currently alarming levels of AMR is the realistic goal that we aim to achieve as a global community, as AMR will always exist, being a natural phenomenon exacerbated by the overuse of antimicrobials in humans, animals, and plants. The concept of stewardship is challenging, as it can be perceived as abstract. In any case, emphasizing the idea that antimicrobials are common goods that need to be preserved by all of us is essential, as it will ultimately lead to a healthier and more sustainable future. In times when food security cannot be taken for granted, the role of the FAO as a global organization is highlighted in this paper, and its multiple initiatives, projects, studies, and campaigns are presented.


The mechanism of the sulfonation reaction with PBz nanofibers was proposed with only one sulfonic acid (–SO3H) group attached to each of the repeating units since only first type substitution in the aromatic structure occurs under this condition. The kinetics of the reaction exhibited a logarithmic correlation where the rate of change in the ion exchange capacity (IEC) with the reaction time increased rapidly and then reached a plateau at the reaction time between 18 h and 24 h. Effective sulfonation was confirmed by electron spectroscopy with a characteristic peak associated with the C–S bond owing to the sulfonate group introduced onto the surface of the nanofibers. ATR-FTIR spectroscopy also confirmed these results for varying reaction times. The SEM images showed that sulfonation has no drastic effects on the morphology and microstructure of the nanofibers but a rougher surface was evident due to the wetted fibers with sulfonate groups attached to the surface. EDX spectra exhibited sulfur peaks where the concentration of sulfonate groups present in the nanofibers is directly proportional to the reaction time. From surface wettability studies, it was found that the nanofibers retained the hydrophobicity after sulfonation but the inherent surface property of PBz nanofibers was observed by changing the pH level of water to basic, which switches its surface properties to hydrophilic. The thermal stability of the sulfonated nanofibers showed almost the same behavior compared to non-sulfonated nanofibers except for the 24 h sulfonation case, which has slightly lower onset temperature of degradation.Electrospun nanofibers of polybenzoxazines (PBzs) were fabricated using an electrospinning process and crosslinked by a sequential thermal treatment. Functionalization by the direct sulfonation process followed after the post-electrospinning modification treatment. The first stage of experiment determined the effects of varying the concentration of sulfuric acid as the sulfonating agent in the sulfonation reaction under ordinary conditions. The second stage examined the mechanism and kinetics of the sulfonation reaction using only concentrated H Functionalization of PBz by electrospinning of nanofibers then thermal crosslinking followed by direct sulfonation process. For the polymerization of PBz, functional groups such as thiol compounds were incorporated for its direct modification to reduce the temperature requirement of ROP and provide enhancement of the thermal and mechanical properties.1 Another effective approach studied for functionalization was the synthesis of PBz from benzoxazine monomers containing other polymerizable groups9 such as ethynyl or phenyl ethynyl,10 nitrile,11 and propargyl groups.12 But, aside from the modification of benzoxazine monomers during the synthetic phase, different strategies of functionalization such as preparation of polymer blends and composites, hybridization with inorganic materials, and chemical incorporation of the benzoxazine structure into the polymer have also been reported.2 Several works involve the blending of PBz with other polymers such as rubber,13 polycarbonate (PC),14 polyurethane (PU),15 poly(ε-caprolactone) (PCL),14 and poly(S-r-diisopropenylbenzene) (SDIB),16 which resulted in the modification of the functional properties derived from the synergy of polymer components. In the previous study of Li and Liu,8 a composite of polybenzoxazine (PBz)-modified polybenzimidazole (PBI) nanofibers showed enhancement in the mechanical strength using PBz as the crosslinking agent. However, the addition of functional groups during PBz synthesis or the formation of copolymers and composite as the modification methods produced mostly beneficial effects but may also have some negative influences on other properties of the final materials.3PBz, as a polymerization product, plays a special role among the class of highly-crosslinked polymers having benzoxazine  in their structures.17 In some polymers such as PBz, application of thermal treatment also causes crosslinking reaction in the polymer structure. Chemical treatment along with physical treatment is applied in order to modify or control the surface properties of the electrospun fibers.18 For surface modification methods, one of the widely used strategies is to introduce chemically active groups on the surface of the nanofiber-based mat through specific chemical reactions.17 Incorporating sulfur-containing functional groups by chemical modification methods have beneficial effects on the physical and chemical properties of the polymer.19 Sulfonation is one of the frequently used methods for modification of the properties for better wettability, higher water flux, higher antifouling capacity, better selectivity, and increased solubility in solvents for processing.20 The simplest sulfonation process is by direct sulfonation using concentrated sulfuric acid (H2SO4) as the sulfonating agent conducted under ordinary conditions.20Electrospinning process was used for the fabrication of PBz nanofibers. Although electrospinning technique is relatively new for fabricating nanomaterials, it is known to enhance the functionality and versatility of nanofibers, which are brought about by the surface morphologies. The thermal treatment of the nanofibers after electrospinning is a physical method of functionalization, which is an effective post-modification strategy for nanofibers.In this study, a different approach of functionalization was explored by the direct sulfonation reaction of electrospun nanofibers that had undergone thermal treatment. Previous studies have investigated the functionalization of PBz by incorporating functional groups during synthesis or by blending and compositing with other polymers and materials. This time, prior to functionalization, PBz was formed into the nanofibers and subjected to successive modification treatment. The PBz nanofibers undergo post-electrospinning thermal treatment, followed by chemical treatment by sulfonation. Thus, this work explores the application of direct sulfonation process to electrospun PBz nanofibers, which, to the best of our knowledge, is the first time such an approach has been used for synthesizing thermally-crosslinked PBz nanofibers. This study examines the nature of chemical interaction between the acid group and the thermally-crosslinked nanofibers, and the effects on the resulting properties, which have not been studied yet. The possible interactions that took place, revealed on studying the mechanism and kinetics of sulfonation, provided a new perspective on the functionalization of PBz nanofibers for applications in separation processes such as in oil–water mixtures.2.2.1et al.21 The synthesized PBz had a number-averaged molecular weight of 4040 g mol−1.22 Concentrated H2SO4  was purchased from Aencore and used as received. Dimethylsulfoxide (DMSO)  and tetrahydrofuran (THF)  were also used as received.Polybenzoxazine (PBz) was prepared in the lab, as reported in the work by Lin 2.2−1 while the applied voltage was 10 kV in relation to the polymer concentration. The electrospinning process was carried out at ambient conditions. The nanofiber mat was obtained in a grounded plate collector with tip-to-collector distance (TCD) of 15 cm. After electrospinning, the electrospun PBz (ES-PBz) nanofiber mat was set aside at ambient conditions for 24 h to vaporize the remaining solvent prior to the post-electrospinning thermal treatment. Then, the nanofiber mat was thermally-crosslinked in an air-circulated drying oven  for sequential thermal treatment with temperatures of 80 °C, 120 °C, 160 °C, 200 °C, and lastly, 240 °C, each for 1 h. Then, the thermally cured mat was cooled down to room temperature inside the oven and then, removed from the collector plate.A homogeneous solution of 10 wt% PBz in a mixture of DMSO and THF (1/3) (v/v) was prepared prior to electrospinning. The nanofiber mat was produced using a vertically-aligned electrospinning apparatus consisting of a 10 mL syringe with a needle (ID = 0.8 mm) connected to a syringe pump, a ground electrode, and a high voltage supply . The needle was connected to the high voltage supply, which generates positive DC voltages up to 40 kV. The electrospinning solution of PBz was placed in the 10 mL syringe, which was ejected through the needle spinneret by a syringe pump with a mass flow rate of 1.00 mL h2.3viz., concentrated and diluted 5 M and 6 M H2SO4, while the other parameters such as the reaction time and temperature were not changed. This part was conducted to establish the most appropriate concentrations of sulfuric acid that effectively modified the surface properties of the nanofibers. Direct sulfonation was conducted according to the procedure described in the work of Esmaielzadeh and Ahmadizadegan.23 The nanofiber mat samples were prepared (approx. 1 cm × 1 cm) from the thermally-crosslinked electrospun PBz nanofibers. Then, the samples were separately immersed in different concentrations of sulfuric acid  at room temperature for 72 h. The ES-PBz samples were removed from sulfuric acid and washed with deionized water repeatedly to remove the residual sulfuric acid until the pH of wash water was > 5. Subsequently, the samples were oven dried  at a temperature of 50 °C for 24 h.A two-stage experiment was carried out for the direct sulfonation process of thermally-crosslinked ES-PBz nanofibers. The first stage of the experiment tested only the one-variable-at-a-time involving the concentration of the sulfonating agent, 2SO4. The same sulfonation procedure was used. Additional post-washing treatment was applied to the membrane samples after sulfonation, as reported from the works of Huang et al.20 In the acetone/water (1/1) (v/v) mixture, the sulfonated membrane samples were immersed for 5 min. Then, the samples were removed from the acetone/water mixture and immersed in pure acetone for 10 min. Subsequently, the samples were oven dried  at a temperature of 50 °C for 24 h.In the first stage, concentrated sulfuric acid was effective in the direct sulfonation of the nanofiber mat samples based on the initial characterization methods. In the second stage of the sulfonation process, variable reaction time was investigated to determine the mechanism and kinetics of reaction. For this stage, the reaction time was varied from 3 h to 6 h and up to only 24 h using concentrated H2.4−1 to 4000 cm−1. SEM-EDX analysis was carried out with a Scanning Electron Microscope (SEM)  with Energy Dispersive X-ray Spectroscopy (EDX)  at the Advanced Device and Materials Testing Laboratory (ADMATEL) of DOST. The water contact angle (WCA) of the electrospun membranes were measured using the water contact angle meter (First Ten Angstroms (FTA) Model: FTA 1000 B) with water drops of about 5 μL under the ambient conditions to evaluate the surface wettability of the electrospun nanofiber surfaces. The contact angle data were obtained from the average of three replicates from five measurements of the samples mounted on specimen glass. The pH level of the water used for determining the contact angle was adjusted from neutral to acidic and basic to further test the surface property.The characterization of the electrospun nanofibers after sulfonation were conducted to evaluate the resulting properties by comparing the non-sulfonated electrospun nanofibers with the samples that undergo the sulfonation reaction. This is to determine if functionalities of the thermally-crosslinked ES-PBz nanofibers were modified or enhanced by the chemical treatment. The samples for testing were prepared according to the methods of characterization that were conducted. For FTIR, a very tiny sample was loaded in the transmission mode after pressing into a KBr disc while ATR was used in conjunction with FTIR to directly examine the portion of the nanofiber mat surface without further preparation. A 5 mm × 10 mm nanofiber mat sample was prepared for mounting and insertion into the instrument to conduct XPS analysis while almost similar size of the dried sample was placed on a carbon tape and gold was coated on the non-conductive nanofiber mat sample for SEM-EDX applications. Surface chemical characterization was performed with an X-ray photo electron spectrometer (XPS) (VG Microtech MT-500 ESCA) analysis to determine the change in the surface chemistry of the material. The resolution of the sub peaks was performed using the least-squares peak analysis software XPS PEAK 95 version 3.0. Attenuated total reflectance (ATR) sampling with Fourier-transform infrared (FTIR) spectra of the electrospun PBz nanofiber mat samples after the sulfonation treatment were obtained using a PerkinElmer Spectrometer at the wavenumbers between 400 cmet al.20 Prior to the back titration procedure, the nanofiber mat samples were prepared by neutralization in 0.01 M sodium hydroxide aqueous solution in the sample to NaOH ratio of 0.025 g/10 mL for 72 h. This fully converted the sulfonated mat samples into their sodium salt form. Then, diluted sulfuric acid with the concentration of 0.003 M was employed to back titrate the NaOH aqueous solution that was partially neutralized by the sulfonated samples. The neutralization point in the back titration was predicted by using a universal indicator. The volume of sulfuric acid used in the titration was used for obtaining the IEC of the samples using 20−1) is the ion exchange capacity (on a dry sample weight basis), V (mL) is the volume and N (mol L−1) is the normality of the sulfuric acid titrating solution, and mdry (g) is the dry mass of the nanofiber mat. The pH of the NaOH solution used for soaking the samples was measured before and after soaking to determine the change in the basicity of the solution.The ion exchange capacity (IEC) was determined using a modified back titration procedure described in the work of Huang 3.3.16,8 The modified nanofiber surface is produced due to the crosslinked fiber structures.24 Crosslinking is a chemical modification treatment of a nanofiber-based mat, which improves the mechanical properties, compactness, and chemical stability.17 In PBz, the cured material possesses low crosslinking density and exhibits near-zero shrinkage due to the removal of strain from ring opening polymerization.2Post-electrospinning treatment is an important thermal curing process for PBz as a physical method of modification prior to the next step functionalization. This curing process applied to the electrospun nanofibers uses sequential thermal treatment and causes improvement in the properties. During thermal curing, the oxazine ring opens by itself without hardeners or a strong acid catalyst.25 For the electrospun nanofibers that were thermally cured, the sulfonate group linkage could endow special features to produce functional nanofibers. To show the effect of using concentrated H2SO4 as the solvent in the sulfonation reaction, both powdered PBz and the as-spun nanofibers of PBz were tested by soaking in the acid. After less than 5 min in H2SO4, the powdered PBz completely dissolved, as shown in 2SO4, also resulted in complete dissolution, as shown in Direct sulfonation process uses sulfuric acid as one of the commonly used sulfonating solvents. The desired outcome for the sulfuric acid reaction during sulfonation is the introduction of sulfonic groups in the nanofibers to a certain degree.2SO4 as a sulfonating agent that affects the stability of the material. Through these solubility tests, the concentration of sulfuric acid was identified as a critical factor in the sulfonation reaction for electrospun nanofibers. To investigate the sulfonation reaction with the thermally-crosslinked PBz nanofiber, the first variable of concern is the acid concentration.These results showed the strength of H3.220 The reaction time was initially set to 72 h with the concentration of sulfuric acid as the only variable from the lower concentration of 5 M and 6 M to concentrated H2SO4 (97%) during the initial experiment of the sulfonation process. As shown in The sulfonation of the electrospun nanofibers was undertaken under ordinary conditions with sulfuric acid as the sulfonating agent. Based on a previous study, using sulfuric acid at room temperature, the reaction occurred at a slower pace, so a long reaction time was needed.2SO4 for a longer reaction time of 72 h also resulted in longer exposure to the reaction and affected the dimensional stability of the sample even if sulfonation was achieved.During the first stage it was found that using concentrated sulfuric acid, the sample formed into a gel during washing with deionized water, as shown in From these observations, the reaction time was shortened to only 24 h for the second stage with concentrated sulfuric acid as the only concentration used to avoid the occurrence of the same condition. The second stage of the experiment involving the sulfonation process established the interactions of the acid group with the nanofibers, which also exhibited the beneficial effect of crosslinking.3.320,26 Based on the previous works, the reaction was found to be second order with respect to SO3 and first order with respect to aromatic compounds.27 The substitution preferentially occurred at the ortho-position of the aromatic ring in the repeating unit of PBz, as shown in 3H) group attached to each of the repeating units since only first type substitution occurs because of the low energy barrier of this sulfonation condition.20In sulfonation, the reaction of the sulfonating agent with the electrospun nanofibers occurred where sulfonic acid was added to the aromatic ring by electrophilic substitutions.20 In addition, the crosslinking reaction in the polymerization of benzoxazines prior to sulfonation proceeds through the electrophilic attack of the ring-opened benzoxazine structure, resulting in the available ortho  and para positions of the neighboring phenolic ring for electrophilic substitution during the sulfonation reaction.28 Although there were no previous works that confirmed the sulfonation of nanofibers PBz, this study proposed that the mechanism of sulfonation reaction is confined to the first type substitution, as shown in On using sulfuric acid as the sulfonating agent, the active site is due to the electron density of the site. The sulfonation reaction at low temperature only occurs in one of the aromatic rings since the electron density of the other aromatic ring in the repeating unit is relatively low due to the neighboring group.29 The ion exchange capacity of the sulfonated electrospun nanofibers of PBz was determined by acid–base titration and compared with the samples sulfonated at different reaction times . At 3 h of the reaction time, the IEC measured was to be 1.78 while at 6 h, it increased 2.03 and obtained the IEC value of 2.27 after 24 h, as presented in IEC is the number of moles of the sulfonate groups (ions) present per gram of the polymer.y is the IEC value and x is the reaction time with a correlation coefficient of 0.9797, indicating strong relationships between the reaction time and the IEC value.The kinetics of sulfonation reaction of electrospun PBz nanofibers was evaluated by determining the correlation of reaction time with the amount of sulfonate groups present in the nanofibers. It exhibited a non-linear correlation and observed that the data is logarithmically related, as shown in However, based on these results, the kinetics of reaction at ordinary conditions confirmed that only the slow reaction took place. The kinetics of reaction with IEC as a function of reaction time exhibited a logarithmic trendline where the rate of change in IEC with the reaction time increased rapidly and then, almost level out or show no significant change in the reaction time between 18 h to 24 h. Further investigation could be undertaken with reaction temperature as another variable.3.42SO4, the same characteristic peaks were observed similar to the non-sulfonated ES-PBz without the presence of the characteristic peak attributed to C–S. Based on the XPS analysis, only the nanofiber samples that were sulfonated using concentrated sulfuric acid, were we to incorporate the sulfonate groups onto the surface of the nanofibers.The sulfonation of the electrospun PBz nanofibers was confirmed using XPS to determine the change in the surface chemistry that occurred in the material. From Further confirmation of sulfonation was obtained from the elemental composition of ES-PBz samples and their relative atomic percentages, as listed in 3.5−1 (asymmetric stretching of C–O–C), 1330–1340 cm−1 (CH2 wagging in the closed benzoxazine ring), and 1495–1510 cm−1 (tri substituted benzene ring) were present.9 For the ES-PBz that undergoes sulfonation as compared to the non-sulfonated ES-PBz, a new peak at 1025–1035 cm−1 was observed, which corresponds to the symmetric stretch of the sulfonate group (SO3). The presence of sulfonate (SO3) group is the result of functionalization of the nanofibers. From the spectra, it was observed that the intensity of the new peak assigned to the sulfonate group was more prominent in the sample that was sulfonated using concentrated sulfuric acid for 24 h as compared to the sulfonated samples at diluted concentration of 5 M and 6 M sulfuric acid at 72 h. This could be the reason for the absence of the sulfonate group, as indicated by the C–S in the XPS analysis of the sulfonated samples at lower concentrations.In order to further confirm the sulfonation reaction with the crosslinked PBz nanofibers, FTIR spectroscopy was carried out to validate the structural composition of the material in comparison with the results of electron spectroscopy. As shown in −1 with almost similar intensity. This characteristic absorption band corresponds to the symmetric stretch of the sulfonate group (SO3), indicating that the sulfonation reaction took place on the samples' surface. This also validated the results of XPS analysis that sulfonate group was only present in the sulfonation reaction using concentrated H2SO4 with the strong intensity of the peak assigned to SO3. Thus, proving that the sulfonation reaction under ordinary conditions with shorter reaction time (3–24 h) resulted in surface modification of the electrospun PBz nanofibers.For the second stage of sulfonation using only concentrated sulfuric acid with varied reaction times of 3 h, 6 h, and 24 h, attenuated total reflectance (ATR) with Fourier transform infrared (FTIR) spectroscopy was used to directly measure the change in the surface chemistry on the nanofiber mat surface and to validate the sulfonation process of the samples at lower reaction times. The ATR-FTIR spectra in 3.6−1).25 This could be the reason for the few broken fibers in the mat samples. In addition, a rougher surface was observed in the nanofibers, which could be the result of the wetted fibers with the sulfonate group that is attached to the nanofibers' surface after the sulfonation reaction.The SEM images of the non-sulfonated electrospun PBz nanofibers in The EDX spectra were then analyzed to determine the overall chemical composition and the distribution of the chemical elements of interest in the sulfonated electrospun nanofibers. The EDX spectra of the non-sulfonated ES-PBz, as expected, show no presence of the sulfur element in the nanofibers whereas the carbon element predominantly appeared, as shown in 3.720 If the sulfonation reaction was successful in incorporating sulfonate groups on the nanofibers' surfaces, then there is an expected change in the hydrophobicity of the ES-PBz nanofibers. Non-sulfonated ES-PBz nanofibers are hydrophobic with a water contact angle of 130° based on the previous work of Parreño et al.16 The crosslinking that occurred in the PBz nanofibers during thermal treatment is known to be an effective method to change the morphology as well as the surface properties of the polymers.20 However, pure PBz nanofibers retained their hydrophobicity even after undergoing post-electrospinning thermal treatment.Contact angle is an important functional property of a material. The change in the contact angle indicates a modification in the surface chemistry.2 The ultralow surface-energy of the crosslinked PBz nanofibers is the result of the hydrogen bonding, which is mainly responsible for the surface properties.22In this study, the water contact angles of the nanofiber mat samples were determined to know if there was an effect on the surface chemistry, as indicated in the IR and electron spectroscopy after the sulfonation process. The contact angles were measured for the non-sulfonated and sulfonated samples at different reaction times for comparison. The results showed that the non-sulfonated, thermally-crosslinked ES-PBz retained its hydrophobicity with a contact angle of 130.03°, as shown in 22 The pH level of water used for the measurements of water contact angle were adjusted to acidic (pH: 3 and 6) and basic (pH: 12 and 14) to examine this surface property. At acidic pH of water, the contact angles at pH 3 and 6 were 127.32° and 129.16°, respectively, as shown in Surface wettability of the sulfonated samples at 24 h reaction time was further characterized by adjusting the pH level of water from acidic to basic to confirm another surface property of the thermally-crosslinked ES-PBz. From a previous study, it was found out that crosslinked PBz has an intrinsically stimuli responsive characteristic due to the hydrogen bonding, which can be broken by changes in pH level of water.This is the validation of the surface properties of the ES-PBz nanofibers, which switch to hydrophilic when the pH of water changes to highly basic. This functional property of the sulfonated PBz nanofibers has potential applications in oil–water separation as they have stimuli responsive surfaces and combined enhancement obtained from the crosslinking and electrospun fiber structure and morphology.3.8The thermal stability of the sulfonated electrospun nanofibers of PBz at different reaction times of 3 h, 6 h, and 24 h were compared to the non-sulfonated electrospun nanofibers to determine the influence of the sulfonation reaction on the nanofibers' stability. Based on the TGA thermograms, as shown in 4.This study provides a new perspective on the functionalization of nanofibers of PBz prepared by the electrospinning process by direct sulfonation reaction using sulfuric acid as the sulfonating agent. The crosslinking of PBz nanofibers by post-electrospinning thermal treatment showed its contributing factor in accommodating the succeeding sulfonation reaction. The mechanism of incorporating the functional groups onto the surface of the PBz nanofibers was analyzed and proposed as first type substitution of sulfonic acid in the aromatic ring, which was effectively carried out using concentrated sulfuric acid. The kinetics of the sulfonation process exhibited a logarithmic correlation where the rate of reaction is time dependent. But with low energy barrier under ordinary sulfonation conditions, it occurred at a slower pace and reached a plateau between the reaction time of 18 to 24 h. The microstructures and morphology after undergoing the sulfonation process were unchanged but had few broken fibers and rougher nanofibers due to the wetted fiber surfaces with the added sulfonate groups. The surface wettability of the nanofibers after sulfonation retained the hydrophobicity and revealed the intrinsic stimuli responsive property of the nanofibers on changing the pH of water to basic. Thermal stability was retained for 3 h and 6 h reaction time in comparison to the non-sulfonated nanofibers. Thus, a simple and easy yet effective functionalization method that can be carried out on crosslinked PBz nanofibers without compromising their form and stability has potential for the targeted applications although further study on other parameters of the sulfonation reaction is needed to achieve the desired results.There are no conflicts to declare.