Viscoelasticity and Birefringence of Polymer Blends (Commemoration Issue Dedicated to Professor Ken-ichi Katayama On the Occasion of His Retirement) (original) (raw)

The birefringence in the process of stress relaxation was investigated for solutions of mixtures of polystyrene (PS) and poly(vinyl methyl ether) (PVME) in dibutyl phthalate. Molecular weight (M,) of PVME was 6.5 x 104, and M of the PS samples were 2.0 x 10', 6.0 x 10', and 9.5 x 10'. The concentrations of PS and PVME were, respectively, 0.30 gcm 3. The birefringence, An, and the shear stress, a, were measured after an instantaneous shear deformation. Under assumptions that the On and y are sums of independent contributions from PS and PVME chains, and that the stress-optical law holds good for the contribution from each chain, the shear stresses, aps and apyME, attributable to the PS and PVME chains, respectively, were separately evaluated. It was found that at long times apyME had relaxed and the stress was supported solely by PS-PS entanglements, in accord with the previous results of viscoelasticity measurement. The stress supported by the PVME chains, apyME, was not affected by varying molecular weights of PS.