Influence of the Addition of Polystyrene-block-poly(methyl methacrylate) Copolymer (PS-b-PMMA) on the Morphologies Generated by Reaction-Induced Phase Separation in PS/PMMA/Epoxy Blends

Abstract

Homogeneous solutions of polystyrene (PS) and poly(methyl methacrylate) (PMMA) in diglycidylether of bisphenol A, containing about 8 wt.-% total thermoplastic, and with or without 0.5 wt.-% of a PS-b-PMMA block copolymer, were polymerized in two ways (i) in the presence of a tertiary amine (benzyldimethylamine, BDMA), or (ii) using a stoichiometric amount of a diamine (4,4′-diaminodiphenyl sulfone, DDS). A double phase-separation was recorded by light transmission during polymerization. A PS-rich phase was separated at low conversions and a PMMA-rich phase was segregated at more advanced conversions. The addition of the block copolymer produced significant changes in the morphologies generated. For the BDMA-initiated polymerization, the presence of the block copolymer made the small PMMA-rich domains clearly discernible in transmission electron microscopy (TEM) micrographs. For the DDS-cured system, the addition of the block copolymer led to a dispersion of small PS-rich particles encapsulated by PMMA shells. The possibility of generating a stable dispersion of biphasic particles by polymerization-induced phase separation opens a new way to modify thermosetting polymers for toughening purposes.