XE-129 NMR-STUDY OF FREE-VOLUME AND PHASE-SEPARATION OF THE POLYSTYRENE POLY(VINYL METHYL-ETHER) BLEND/

The polystyrene/poly(vinyl methyl ether) (PS/PVME) blend is studied by ID and 2D Xe-129 n.m.r. The signal of Xe dissolved in miscible PS/PVM E blends exhibits a single peak, and the chemical shift shows non-line ar dependence on the PVME content. The observed dependence is explaine d by the decrease of the total volume of the blend with the increasing PVME content. In the blend heated above the lower critical solution t emperature, the single Xe-129 peak splits into two peaks, which can be ascribed to the PS-rich and PVME-rich phases. The observed chemical s hifts of a phase-separated blend provide the component ratios of each separated phase at the initial stage. Further, 2D exchange Xe-129 n.m. r. measurements for the phase-separated blends heat-treated for variou s periods are performed to determine the average domain sizes of the P S-rich and PVME-rich phases. (C) 1997 Elsevier Science Ltd.