Preparation and properties of cryogel based on poly(hydroxypropyl methacrylate)
Abstract A novel supermacroporous poly(hydroxypropyl methacrylate) (p(HPMA)) cryogel was synthesized by cryogelation method at –16 °C. In this synthesis process, HPMA was used as a monomer, and N,N′-methylenebisacrylamide (MBAAm) was used as cross-linker; the reaction was carried out in the presence of redox initiator pair N,N,N′,N′-tetramethylene diamine (TEMED) and ammonium persulfate (APS). The effect of monomer concentration, cross-linker content, cooling rate, and dioxane co-solvent were determined with respect to the pore structure, mechanical behavior, swelling degree, and porosity of cryogel. The ESEM images indicate that the pore wall structure of cryogels was rough; moreover, small holes were present in the pore walls of cryogels. The result of compression test indicates that cryogels can be compressed by at least 80% without any breakdown. The result of swelling kinetics indicates that cryogels attain swelling equilibrium in 10 s. Furthermore, p(HPMA)-Cu2+ cryogel was prepared by loading Cu2+ ions on functionalized poly(hydroxypropyl methacrylate)-iminodiacetic acid (p(HPMA)-IDA) cryogel. We investigated the adsorption of bovine serum albumin (BSA) on cryogels. The results indicate that compared to Freundlich isotherm, Langmuir isotherm could more suitably describe the adsorption process of BSA on cryogels. Meanwhile, the adsorption capacity of p(HPMA)-Cu2+ cryogel was significantly greater than that of p(HPMA) cryogel. The maximum adsorption capacity of BSA on p(HPMA)-Cu2+ cryogel, which was treated with 1 M Cu2+ ions, was as high as 196.87 mg/g cryogel (equivalent to 20.48 mg/mL cryogel) at 25 °C and pH = 7.8; therefore, the maximum adsorption capacity of BSA on p(HPMA)-Cu2+ cryogel was 4.35 times higher than that of p(HPMA) cryogel. Thus, the adsorption capacity of cryogels was strongly influenced by Cu2+ concentration, moreover, temperature changes clearly affected the adsorption capacity of p(HPMA)-Cu2+cryogel. The adsorption capacity at 25 °C was twice as that at 15 °C. By calculating Gibbs free energy change (∆G) of adsorption, we found that the adsorption process was spontaneous; moreover, adsorption process occurred better at higher temperature.
Preparation and Properties of Cryogel Based on Poly(2-hydroxyethyl methacrylate- co-glycidyl methacrylate).
The immobilized metal affinity cryogels based on poly(2-hydroxyethyl methacrylate- co-glycidyl methacrylate) (p(HEMA-GMA)) containing hydroxy and epoxy groups were prepared by free-radical copolymerization under cryogenic condition and then functionalized with iminodiacetic acid and chelated Cu2+, Ca2+, and Fe3+ ions to the p(HEMA-GMA) cryogel. The structures of p(HEMA-GMA) and immobilized metal-affinity cryogels were analyzed by Fourier transform infrared spectroscopy and scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy. SEM results showed that the prepared cryogels had interconnected pores with the size of 30-100 μm. The performance of water swelling into the cryogels was fitted in Fickian diffusion. The adsorption property of cryogels was influenced by the immobilized ionic type, temperature, and adsorbate. The adsorption capacity of immobilized Cu2+ cryogel (p(HEMA)-Cu2+ (0.5 M) cryogel) was the highest in comparison with that of Ca2+ and Fe3+ affinity cryogels under the same condition. The maximum adsorption capacity of p(HEMA)-Cu2+ (0.5 M) cryogel for porcine pancreatic lipase was 150.14 mg/g at a higher temperature of 35 °C, whereas for bovine serum albumin, the maximum adsorption capacity was 154.11 mg/g at a lower temperature of 25 °C. The research of thermodynamics and kinetics indicated that the mechanism of the protein adsorption process corresponded to the Langmuir model and pseudo-second-order model.
The Impact of the Law of the Sea Convention on the Regime for Islands: Problems for the Coastal State in Asserting Claims to “New-Born” Islands in Maritime Zones
ter-productive. The work of the Preparatory Commission will certainly suffer in consequence and the apparently perceived belief that in time, and before a longdelayed coming into force of the Convention, substantial re-negotiation of the Part XI provisions will be possible, may well be illusory. At the time of writing, 138 countries have signed the Convention and 14 have ratified.* What has been called "the convoluted compromise" over prospective Community participation will certainly be widely interpreted as an attempt by the Federal Republic of Germany and the United Kingdom to secure eventually a form of limited accession with major reservations.* Their stance will be subjected to criticism within the Community as well as in the General Assembly and the Preparatory Commission. This is a subject to which the writer hopes to return in a future article. For the moment, however, it is as well to note that the stance of these two countries is not to be identified with the US position although its adoption now makes even more remote the emergence of a deep sea-bed mining regime established by " . . . an international treaty of a universal character, generally agreed upon . . . " as required by the 1970 General Assembly Declaration of Principles Governing the Sea-Bed . . . Beyond the Limits of National Jurisdiction.*