Miscibility and crystallization behavior in blends of poly(methyl methacrylate) and poly(vinylidene fluoride): Effect of star-like topology of poly(methyl methacrylate) chain

A tetraarmed star-shaped poly(methyl methacrylate) (s-PMMA) was synthesized via atom transfer radical polymerization with 2-bromoisobutyryl pentaerythritol as the initiator. For comparison, a linear PMMA with the identical molecular weight (l-PMMA) was also prepared. The blends of the two PMMA samples with poly (vinylidene fluoride) (PVDF) were prepared to investigate the effect of macromolecular topological structure on miscibility and crystallization behavior of the binary blends. The behavior of single and composition-dependent glass transition temperatures was found for the blends of s-PMMA with PVDF, indicating that the s-PMMA is miscible with PVDF in the amorphous state just like l-PMMA. The miscibility was further evidenced by the depression of equilibrium melting points. It is found that the blends of s-PMMA and PVDF displayed the larger k value of Gordon-Taylor equation than the blends of l-PMNU and PVDF blends. According to the depression of equilibrium melting points, the intermolecular parameters for the two blends were estimated. It is noted that the s-PMMA/PVDF blends displayed the lower interaction parameter than l-PMMA/PVDF blends. The isothermal crystallization kinetics shows that the crystalhzation of PVDF in the blends containing s-PMNIA is faster than that in the blends containing the linear PMMA. The surface-folding free energy of PVDF chains in the blends containing s-PMMA is significantly lower than those in the blends containing I-PMMA. (c) 2007 Wiley Periodicals, Inc.