Resonantly enhanced off-specular X-ray scattering from polymer/polymer interfaces⋆
Abstract.We have used measurements of the absolute intensity of diffuse X-ray scattering to extract the interfacial tension of a buried polymer/polymer interface. Diffuse scattering was excited by an X-ray standing wave whose phase was adjusted to have a high intensity at the polymer/polymer interface and simultaneously a node at the polymer/air interface. This method permits the capillary-wave-induced roughness of the interface, and hence the interfacial tension, to be measured independently of the polymer/polymer interdiffusion.
FORMYLATION OF PENDENT AROMATIC GROUPS ATTACHED TO LINEAR POLYMER CHAINS
La formylation par MeOCHCl 2 /TiCl 4 dans CS 2 du polystyrene, du poly(1-vinylnaphtalene), du poly(9-vinylphenanthrene) et du poly(1-vinylpyrene) donne avec de bons rendements des polymeres lineaires de degre de substitution eleve, sauf pour le polystyrene ou on observe une reticulation plus importante. Cette methode est applicable aux polymeres vinyliques lineaires ou reticules portant des groupes lateraux aromatiques. Le degre de formylation des polymeres portant des cycles aromatiques condenses est controlable en variant les proportions des reactifs
A Critical Assessment on Functional Attributes and Degradation Mechanism of Membrane Electrode Assembly Components in Direct Methanol Fuel Cells
Direct methanol fuel cells (DMFC) are typically a subset of polymer electrolyte membrane fuel cells (PEMFC) that possess benefits such as fuel flexibility, reduction in plant balance, and benign operation. Due to their benefits, DMFCs could play a substantial role in the future, specifically in replacing Li-ion batteries for portable and military applications. However, the critical concern with DMFCs is the degradation and inadequate reliability that affect the overall value chain and can potentially impede the commercialization of DMFCs. As a consequence, a reliability assessment can provide more insight into a DMFC component’s attributes. The membrane electrode assembly (MEA) is the integral component of the DMFC stack. A comprehensive understanding of its functional attributes and degradation mechanism plays a significant role in its commercialization. The methanol crossover through the membrane, carbon monoxide poisoning, high anode polarization by methanol oxidation, and operating parameters such as temperature, humidity, and others are significant contributions to MEA degradation. In addition, inadequate reliability of the MEA impacts the failure mechanism of DMFC, resulting in poor efficiency. Consequently, this paper provides a comprehensive assessment of several factors leading to the MEA degradation mechanism in order to develop a holistic understanding.