MISCIBILITY OF POLY(PARA-PHENYLENE VINYLENE) MODEL COMPOUNDS WITH PMMA STUDIED BY SOLID-STATE NMR

Abstract

Molecular proximity of trans, trans-1,4-bis(2-(3,4,5-trimethoxyphenyl)ethenyl)benzene (MPV) and poly(methyl methacrylate) (PMMA) in MPV-poor mixtures up to a weight ratio MPV/PMMA = 1/1.5 is shown by H-1 combined rotation and multiple pulse spectroscopy (CRAMPS) using 2D exchange experiments. The MPV-rich blends (MPV/PMMA = 1/1.4, 1/1.2) are heterogeneous, but have homogeneous domains, while the blend with a weight ratio MPV/PMMA = 1/0.7 is fully heterogeneous. The comparison of the CP/MAS C-13 NMR spectra of pure MPV and of MPV blended with PMMA shows significant changes in chemical shift and line broadening in the case of intimate mixing, whereas heterogeneity causes an increase of resolution. This was confirmed by proton spin-locking relaxation time measurements (T1-rho-H) on the blends. On intimate mixing, T1-rho-H is averaged out and varies linearly as a function of blend composition.