ISOTOPE EFFECTS ON THE PHASE-SEPARATION IN POLYSTYRENE POLY(VINYL METHYL-ETHER) BLENDS .2. INFLUENCE OF THE MICROSTRUCTURE OF LINEAR AND STAR BLOCK-COPOLYMERS

Phase separation trends in blends of poly(vinyl methyl ether) (PVME) w ith various hydrogenous block-deuterated polystyrenes (PS) have been s tudied by a fluorescence technique. In the case of linear polystyrenes of a given overall chain length and deuterium content, the position o f the LCST-type phase diagrams in the temperature-composition plane is shown to depend on whether the deuterated block is located in the mid dle or at the end of the chain. Additionally, it is observed that the kinetics of spinodal decomposition differ from one system to the other . The inspection of the phase behavior of mixtures, including star-sha ped hydrogenous-block-deuterated PS's, and the investigation of the so lubility properties of the PS copolymers in a monomeric analog of PVME support the idea that the polymer-polymer interaction parameter depen ds on copolymer morphology, namely, on the accessibility of the ether functions to the thermodynamically-favored deuterated phenyl rings of polystyrene.