Solid-state NMR observation of polymer blends and interphases

4 Solid-state NMR observation of polymer blends and interphases 

As the use of polymers continues to increase in multi-component and multiphase applications, such as in polymer blends and composites, the behavior of polymers at interphases and the degree of mixing polymer segments in their blends become critical issues. Understanding how the conformations and mobilities of polymer chains in these heterogeneous systems compare with those observed in their homogeneous bulk systems may provide a point of departure in the discussions of their physical characteristics. 

The PIPA chains in a bulk sample observed at ambient temperature, which is approximately 30°C above the Tg of PIPA, are probably sufficiently mobile to make the cross-polarization process inefficient. PIPA chains attached to 

Deuteration of one polymer component, either one homopolymer in a blend, or one block of a copolymer, can also be utilized to study phase separation. In cross-polarized experiments, such as CPMAS/DD or the deuterated species will not appear in the spectrum for heterogeneous samples, or will be observed but with the relaxation time of the protonated component for homogeneous samples. 

Sankar et al [48] have studied A/B block copolymers of polystyrene (PS) and poly(methylmethacrylate) (PMMA) by observation of C-detected where neither, one or the other, and both blocks were perdeuterated. They found that the carbons in each block of the copolymers were experiencing primarily their own protons, indicating some degree of phase separation, but the for each block differed somewhat from the measured for the PS and PMMA homopolymers. Annealing quenched samples apparently increased the degree of phase separation, because their values more closely approached the homopolymer values. 

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