Polymer-Poly -cast function

Importantly, for elevated temperature PEM fuel cell operation, the HPAs may be structurally stable to >600°C, although under anhydrous conditions their stability may be limited to 200°C, and they incorporate some water molecules and protons up to >300°C depending on the system [15]. Because of their structural diversity, these materials are particularly suitable for incorporation into a wide variety of membrane materials for which they can be specifically tailored. They have been studied in four composite systems HPAs infused into perfluorinated sulfonic acid (PFSA) polymers such as Nafion [16,17], HPA cast in inert matrices such as poly (vinyl alcohol) (PVA) [18], HPA immobilized in polymer/silicate nanocomposites via sol-gel methods [19], and HPA directly incorporated into polymer films via functionalization to monomers [20]. Here after a discussion of fundamental studies, we review the various HPA-based materials used for fuel cells. 

The blend of poly(bisphenol A carbonate)-(poly(caprolactone) PC-PCL is particularly unusual in that both polymers are capable of crystallization and FT-IR has been used to study the state of order in these blends as a function of the method of preparation 254,255). In this case, PCL is a macromolecular plasticizer for PC. The PCL becomes progressively less crystalline as the concentration of PC increases. PC is amorphous if the blend is cast from methylene chloride but semicrystalline if cast from tetrahydrofuran. When PC in the pure form is exposed to acetone, it will not crystallize, but in the blend, exposure of acetone causes the PC to crystallize which emphasizes the additional mobility of the PC in the blend. 

Depth-distribution of fluorescent dopants in cast polymer film (4) Fluorescence spectra of poly(N-vinylcarbazole) (PVCz) film doped with perylene are shown in Fig. 6. They consist of two broad structureless excimer bands of the polymer with a shoulder at 375 nm and a peak at 420 nra, and perylene band with a vibrational structure above 450 nm. It is worth noting that the perylene fluorescence intensity under the TIR condition is relatively weaker than that under the normal one. Since the boundary surface is selectively excited under the former condition, the structure near the surface should be different from the bulk. It is well known that the excitation energy migrates over carbazolyl chromophores and is trapped in the doped perylene efficiently. Therefore, the present result means that energy migration efficiency in the host polymer and/or the dopant concentration are a function of the depth from the interface. 

Two-dimensional deuteron NMR was used to analyze miscibility in blends of poly-1,4-polyisoprene with polyvinylethylene (PIP/PVE) [Arendt et al., 1994 Chung et al, 1994]. The blends were prepared by casting 3 wt% toluene solution. The rate of reorientation as a function of temperature near T was determined for both components. It was found that the system is miscible, but the glass transition is broad owing to the wide distribution of segmental motions arising from the differences in the rates of the two polymers. As a result, the PIP/PVE blends were found to be rheologically complex. In spite of miscibility the time-temperature superposition was found to be invalid. 

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