SPECTROSCOPIC INVESTIGATIONS OF SPECIFIC INTERACTIONS IN AMORPHOUS POLYMER POLYMER BLENDS - POLY(VINYLPHENOL) AND POLY(VINYL METHYL KETONE)

Poly(4-vinylphenol)(PVPh), a proton donor, and poly(vinyl methyl ketone) (PVMK), a proton acceptor, represent an illustrative example of hydrogen-bonding-induced miscibility in amorphous polymer-polymer blends. The infrared vibrational absorptions of the OH group in PVPh and the ketone carbonyl moiety in PVMK reveal that site-specific interactions are operative between dissimilar chain segments in the blended states. High-resolution carbon-13 solid-state NMR spectroscopy provides further evidence for strong interaction and molecule-for-molecule mixing between the two components. Poly(vinylphenol)'s phenolic carbon NMR chemical shift can distinguish two types of segment interactions via resonances that differ in their peak positions by approximately 2-3 ppm. Both spectroscopic probes, FTIR and C-13 solid-state NMR, reveal that overlapping signals persist when the hydrogen bond between dissimilar functional groups in the amorphous state competes with the self-association of PVPh's hydroxyl group. The line width of the phenolic carbon NMR signal is a strong function of blend composition, particularly when the lower T(g) component, PVMK, is present in excess. From a macroscopic viewpoint, the single glass transition process for each blend investigated is consistent with the spectroscopic results.