Effect of Tacticity of Poly(methyl methacrylate) on the Miscibility with Poly(styene-co-acrylonitrile)

摘要

Isotactic,atactic,and syndiotactic poly(methyl methacrylates) (PMMAs) (designated as iPMMA,aPMMA,and sPMMA) with approximately the same molecular weight were mixed separately with poly(styrene-co-acrylonitrile) (abbreviated as PSAN) containing 25 wt % of acrylonitrile in tetrahydrofuran to make three polymer blend systems.Differential scanning calorimetry (DSC) was used to study the misci-bility of these blends.The results showed that the tacticity of PMMA has a definite impact on its miscibility with PSAN.The aPMMA/PSAN and sPMMA/PSAN blends were found to be miscible because all the prepared films were transparent and showed composition dependent glass transition temperatures (T_gs).The glass transition temperatures of the two miscible blends were fitted well by the Fox equation,and no broadening of the glass transition regions was observed.The iPMMA/PSAN blends were found to be immiscible,because most of the cast films were translucent and had two glass transition temperatures.Through the use of a simple binary interaction model,the following comments can be drawn.The isotactic MMA segments seemed to interact differently with styrene and with acrylonitrile segments from atactic or syndio-tactic MMA segments.