MOLECULAR-MOTION IN MISCIBLE POLYMER BLENDS .1. MOTION IN BLENDS OF PEO AND PVPH STUDIED BY SOLID-STATE C-13 T-1-RHO MEASUREMENTS

Changes in molecular motion in blends of PEO-PVPh have been studied us ing measurements of C-13 T-1 rho relaxation times. C-13 T-1 rho relaxa tion has been confirmed as arising from spin-lattice interactions by o bservation of the variation in T-1 rho with rf field strength and temp erature. In the pure homopolymers a minimum in T-1 rho is observed at ca. 50 K above the glass transition temperatures detected by DSC. Afte r blending, the temperature of the minimum in T-1 rho for PEO increase d, while that for PVPh decreased, however, the minima, which correspon d to the temperatures where the average correlation times for reorient ation are close to 3.1 mu s, are separated by 45 K (in a 45% PEO-PVPh blend). These phenomena are explained in terms of the local nature of T-1 rho measurements. The motions of the individual homopolymer chains are only partially coupled in the blend. A short T-1 rho has been obs erved for protonated aromatic carbons, and assigned to phenyl rings un dergoing large-angle oscillatory motion, The effects of blending, and temperature, on the proportion of rings undergoing oscillatory motion are analyzed.