Thermally induced phase separation of polystyrene‐poly(vinyl methyl ether) mixtures

Abstract

Past differential scanning calorimetry and dielectric relaxation measurements have established that polystyrene (PS)‐poly(vinyl methyl ether) (PVME) mixtures exhibit a degree of compatibility when cast from toluene, whereas they are incompatible when cast from chloroform or trichloroethylene. The present study reports that toluene‐cast mixtures can be phase‐separated by thermal treatment at temperatures exceeding 125°C. This is true for samples containing 20–80 wt‐% PS. The temperature of phase separation varies with heating rate; isothermal heating times needed to cause phase separation increase rapidly as the temperature approaches 125°C. Reversibility of the phase separation process depends upon such factors as cooling rate, annealing time, treatment temperature, and thermal history. By annealing and/or slow cooling, all thermally phase‐separated mixtures have been brought back to their original state of compatibility. That is, there is no evidence for true irreversiblity of phase separation in thermally treated samples. Quench‐cooled samples remain phase‐separated indefinitely at room temperature, but this is attributed to rapid cooling below the glass transition of the PS. Chloroform‐cast and trichloroethylene‐cast mixtures have not been brought to a compatible state by thermal treatment, even after lengthy annealing and slow cooling steps.

Blendas de PHB e seus copolímeros: miscibilidade e compatibilidade

“…É o caso das blendas de poliestireno e poli(vinilmetiléter), reconhecidamente miscíveis, que preparadas a partir de solução em clorofórmio resultam em misturas heterogêneas. 22,23 No caso de uma blenda imiscível, contendo baixos teores de um componente, ou apresentando uma fase com dimensões reduzidas, a detecção da transição vítrea pode ser comprometida pela sensibilidade inadequada da técnica experimental utilizada. Geralmente, quando um componente da blenda está finamente disperso na matriz do outro componente, a análise dinâmico-mecânica consegue discriminar duas transições vítreas melhor do que a técnica de DSC.…”

Marginal miscibility and solvent-dependent phase behavior in solution-blended poly(vinyl methyl ether)/poly(benzyl methacrylate)

“…Poly(vinyl methyl ether) (PVME)/polystyrene (PS) blend, which has been extensively studied [1][2][3] , is a well-known classical example of polymer-polymer miscibility. More recently, PVME has also been proven to be miscible with syndiotactic s-PS 4) as well as with isotactic i-PS 5) .…”

Late Stages of Phase Separation in a Binary Polymer Blend Studied by Rheology, Optical and Electron Microscopy, and Solid State NMR

“…The miscibilities of PS and PVME were demonstrated by the observations of a single T g at all compositions for temperatures below the LCST (about 100°C). 4,5 In 1974, Kwei, Nishi, and Roberts 6 determined the composition of each phase-separated domain of a 50/50 PS/PVME blend by measuring the 13 C NMR spin-lattice relaxation time of single-phase and two-phase blends.…”