Influence of the Tacticity of Poly(methyl methacrylate) on Its Miscibility with Chlorinated Polymers

Differential scanning calorimetry was used to determine the miscibility behavior of poly(methyl methacrylate) (PMMA)/chlorinated polymer blends. Nine PMMA's differing in tacticity were blended with three chlorinated polymers: poly(vinyl chloride) (PVC), a chlorinated PVC having a chlorine content of 68% (CPVC), and Saran, which is a random copolymer of vinyl chloride (12%) and vinylidene chloride (88%). The results show that all these PMMA's are miscible with PVC, CPVC, and Saran under proper thermal treatments and especially at 298 K. They all exhibit a lower critical solution temperature (LCST) which varies as a function of the microstructure of PMMA and the chlorine content of the chlorinated polymer. This LCST increases with the syndiotactic content for PMMA's blended with PVC or CPVC but decreases with the syndiotactic content of PMMA for Saran/PMMA blends. An increase in the chlorine content of the chlorinated polymer results in a decrease of the temperature of phase separation except for highly isotactic PMMA where the temperature of phase separation increases with the chlorine content. When the sample is annealed between its LCST and its Tg, miscibility is obtained. When the sample is annealed above its LCST, phase separation occurs. Correlations are made between the phase behavior of these polymer blends and the specific interactions occurring between them. © 1988, American Chemical Society. All rights reserved.