Miscibility with Asymmetrical Interactions in Blends of Two Carbonyl‐Containing Polymers: Poly(vinyl acetate) with Aliphatic Polyesters

Abstract Summary: Phase behavior, miscibility, or immiscibility in blends of two polymers with carbonyl groups, PVAc and homologous polyesters of different CH 2 /CO ratios, were examined using DSC, OM and SEM. Polyesters used in this study included PES, PEA, PPA, and PBA. PVAc/polyester blends were found to be immiscible with distinctly a two‐phase morphology when the polyesters' structural CH 2 /CO ratios are lower than 3 or higher than 4; whereas miscibility is seen in three blend systems: PVAc/PEA (CH 2 /CO = 3.0), PVAc/PPA (CH 2 /CO = 3.5), and PVAc/PBA (CH 2 /CO = 4.0). Asymmetry in the T g ‐composition relationships is seen in all three miscible blend systems. Such non‐specific, weak and asymmetrical interactions, though sufficient to maintain borderline miscibility in the blends, may be partially responsible for leading to the noted asymmetry in the T g ‐composition relation of the blends. Mechanism and origin of this phenomenon of asymmetry in T g ‐composition relationships in some blends may be still puzzling. Strictly speaking, the non‐equilibrium phenomenon of glass transition may not be ideal for evaluating the strength of intermolecular interactions in blends. Future perfection on more suitable approaches may yet be needed. T g vs. composition for the miscible PVAc/PPA blend. magnified image T g vs. composition for the miscible PVAc/PPA blend.