Comparison of glass transition and interpretation on miscibility in blends of amorphous polyvinyl methyl ether with highly crystallizable versus less-crystallizable polyesters

Various phase behavior of blends of poly(vinyl ether)s with polyesters of two types (highly crystalline and less crystalline with different main-chains) were examined using differential scanning calorimetry (DSC) and optical microscopy (OM). Effects of varying the main-chain polarity of the constituent polyesters on the phase behavior of the blends were analyzed. Miscibility in PVME/polyester blends was found only in polyesters with backbone CH ₂/CO ratio = 3.5 to 7.0). T_g-composition relationships for blends of PVME with highly crystalline polyesters (PBA, PHS) were found to differ significantly from those for PVME blends with less-crystalline polyesters (PTA, PEAz). Crystallinity of highly crystalline polyester constituents in blends caused significant asymmetry in the T_g-composition relationships, and induced positive deviation of blends' T_g above linearity; on the other hand, blends of PVME with less crystalline polyesters exhibit typical Fox or Gordon-Taylor types of relationships. The x parameters for the miscible blends were found to range from -0.17 to -0.33, reflecting generally weak interactions. Phase behavior was analyzed and compared among blends of PVME with rapidly crystallizing vs. less-crystallizing polyesters, respectively. Effects of polyesters' crystallinity and structures on phase behavior of PVME/polyester blends are discussed.