Structural morphology effect temperature

Polymers are always polydisperse with a distribution in molar mass and often contain chain branches, either introduced specifically during synthesis or as a consequence of synthetic defects, and both these effects will influence the observed morphology. As we shall see later, copolymers are a special case however, the introduction of low levels of comonomers can lead to behaviour which is rather like that of random branched chains. Different molecular species crystallize in different stages indicating the thermodynamic control on the overall process, i.e. they are incorporated into the crystal structure at different temperatures and times. The intermediate and high molar mass component crystallizes early in the stacks of thick dominant crystals. Small pockets of rejected molten low molar mass material remain after crystallization... 

On the same topic of DMFC performance with supported vs. unsupported catalysts Smotkin and co-workers concluded that at 363 Kthe supported PtRu (1 1) catalyst with a toad of 0.46 mg cm performed as welt as an unsupported PtRu (1 1) with over four times higher load, i.e., 2 mg cm [266]. It is likely that these differences between various studies are related not only to the intrinsic activity of the respective anode catalys layers but also to the manufacturing procedures such as catalyst layer preparation and application techniques, MEA hot pressing conditions (temperature, pressure and time), presence or absence of other binders (such as PTFE) and fuel cell compression. All these MEA manufacturing variables can affect, in a poorly understood manner at present, the structure, morphology and composition of the catalyst layer in the operating fuel cell. Therefore, in fuel cell experiments it is difficult to isolate the truly physico-chemical effect of the support on the catalytic activity. 

Porous scaffolds could be achieved by optimizing the conditions to get interconnected porous structures. The effect of phase separation parameters on scaffold morphology was investigated, including polymer concentration, quenching time, the ratio of dioxane to water, and the freeze temperature. 

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