Double Phase Separation Induced by Polymerization in Ternary Blends of Epoxies with Polystyrene and Poly(methyl methacrylate)

Abstract

Ternary blends based on a stoichiometric mixture of diglycidyl ether of bisphenol A (DGEBA) and 4,4‘-diaminodiphenyl sulfone (DDS), monodisperse polystyrene (PS, 8.3 × 104 g/mol), and monodisperse poly(methyl methacrylate) (PMMA, 8.86 × 104 g/mol) were polymerized at constant temperature. Blends containing a total amount of 8 wt % of both thermoplastics (with different PS/PMMA ratios), were initially homogeneous at 135 °C. When they were polymerized at this temperature, a double phase separation was clearly observed by light transmission. At conversions close to 0.08, the system became opalescent due to the generation of a PS-rich phase; at conversions close to 0.27, a new phase separation process took place, generating a PMMA-rich phase. TEM (transmission electron microscopy) observations confirmed the existence of three different phases: the epoxy matrix, PS-rich particles with a broad size distribution, and PMMA-rich particles. Some of the PS particles appeared encapsulated by the PMMA-rich phase (cor...