Other Physical Chemical Properties of Miscible Blends

Other Physical Chemical Properties of Miscible Blends.—Other workers have been examining the nature of miscible blends and the phase separation process. 

Measurements have been made of the size of the polymer coil in miscible blends, ° using neutron scattering. Some have observed expanded coils and others contracted coils. It has been suggested that this should depend on whether the polymer is glassy or rubbery, i.e., the chain flexibility. The results are not consistent but a definitive set of experiments remains to be done. Studies on PVC show the dominant effect that the small crystalline part of this polymer can play in scattering from its blends. The crystalline regions do not mix with the other polymer and this could greatly affect the properties of PVC blends. 

Some diffusion studies have also been undertaken for compatible systems. Two-phase systems have been annealed and the disappearance of structure observed by microscopy. In another experiment, layers of PVC and poly-caprolactone were contacted and heated at 90 °C. Scanning electron microscopy with chlorine analysis was used to measure diffusion at the interface. Perhaps surprisingly, the results suggest a dependence on (molecular weight). More commonly the diffusion constant scales as (molecular weight)  

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