INTERFACIAL ACTIVITY OF POLYCARBONATE PMMA GRAFT-COPOLYMERS IN POLYCARBONATE PMMA BLENDS - EFFECT OF COPOLYMER CONCENTRATION

This paper discusses the effectiveness of polycarbonate/poly(methyl methacrylate) graft copolymers as emulsifiers in solvent-cast dispersions of poly(methyl methacrylate)/polycarbonate blends. The molecular weight of the copolymer block corresponding to the minor (polycarbonate) phase was distinctly higher than that of the corresponding homopolymer. The results indicate that small amounts (< 5% w/w) of copolymer can act as an effective surfactant, producing fine dispersions and creating significant amounts of interfacial area. Further addition of copolymer into the blend had no effect on the size of dispersed regions or on interfacial area. Dynamic mechanical spectra, microscopy and phase diagrams of the systems provide evidence that additional copolymer causes compositional rearrangement. Although some increased miscibility of the polymer components has been effected by the addition of copolymer in the blend, there is no evidence that the copolymers act primarily as miscibilizers for the blend.