STUDY OF THE ORIENTATION OF POLY(STYRENE) POLY(VINYL METHYL-ETHER) BLENDS RELATIVE TO THE GLASS-TRANSITION TEMPERATURE

Molecular orientation and mechanical properties of poly(styrene)/poly(vinyl methyl ether) (PS/PVME) miscible blends are studied, in a broad range of compositions, taking as a reference the temperature of the glass transition. The PS orientation is directly measured using Fourier transform infrared spectroscopy (FTIR), whereas the orientation of PVME is characterized by coupling FTIR and birefringence techniques. It is observed that the overall and individual orientations, as well as Young's modulus of the blends, remain constant up to 30% PVME. Above this concentration, these properties are found to be strongly composition dependent and to increase at the 50% PVME composition by a factor of 6 (PS orientation), 4 (overall birefringence), and 10 (modulus) as compared to the corresponding values below 30%. This behavior is interpreted in terms of a change in the strength of specific interactions between the dissimilar chains with the blend composition and is analyzed with a simple version of the Doi-Edwards theory.