Poly blends experimental materials

Proton spin-temperature equilibration between the hard- and soft-segment-rich domains of the polyurethane elastomer on the order of 10-100 ms might be considered fast relative to a macroscopically phase-separated blend [26] or copolymer, but slow relative to a strongly interacting mixture [25]. This is reasonable for a microphase-separated material whose solid state morphology has been the subject of considerable theoretical and experimental research. Under fortuitous circumstances, intimate (near-neighbor) contact between dissimilar molecules in a mixture can be studied via direct measurement of proton spin diffusion in a two-dimensional application of the 1H-CRAM PS experiment (Combined Rotation And Multiple Pulse Spectroscopy). Belfiore et al. [17,25,31] have detected intermolecular dipolar communication in a hydrogen-bonded cocrystallized solid solution of poly(ethylene oxide) and resorcinol on the f00-/xs time scale, whereas Ernst and coworkers [26] report the absence of proton spin diffusion on the 100-ms time scale for an immiscible blend of polystyrene and poly(vinyl methyl ether), cast from chloroform. 

Poly(styrene-co-butadiene) rubber and poly(acrylonitrile-co-butadiene) rubber latex mixture films were evaluated as precursors of polymer electrolytes. A 50 50 blend was the optimum for mechanical strength and ionic conductivity. A simple equivalent mechanical model for the relationship between the mechanical strength and the structure was developed, which gave good agreement with experimental results, including materials with co-continuous phase morphologies. 26 refs. 

A quantitative thermal method, based on the differential of heat capacity signal from modulated temperature differential scanning calorimetry, was described for determining the weight fraction of interface and the extent of phase separation in polymer materials. The interface was modelled as discrete fractions, each with its own characteristic increment of heat capacity. The materials used to demonstrate the range of the method were PS blended with poly(phenylene oxide) (PPO), pure PS, pure PPO, a styrene-isoprene-styrene triblock copolymer (SIS), SIS blended with PPO, PMMA/poly(vinyl acetate) blends and PVC sandwiched with poly(n-butyl acrylate). Two-phase and four-phase systems were used. The calculated results agreed well with experimental results for two- and four-phase systems. 20 refs. 

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