Blends containing tetramethyl bisphenol-A polycarbonate: 1. Styrenic polymers

Abstract

The phase behaviour of blends of tetramethyl bisphenol-A polycarbonate, MPC, with styrene copolymers and substituted styrene homopolymers was examined using d.s.c. and optical indications of phase separation on heating, i.e. lower critical solution temperature, LCST, behaviour. MPC was found to be miscible with styrene/acrylonitrile copolymers, SAN, having an AN content smaller than 13%, with a styrene/maleic anhydride copolymer, SMA, having an MA content equal to 8% and with oligomeric styrene/allyl alcohol copolymers, SAA, having an AA content less than 19.1%. MPC was also found to be miscible with an oligomeric poly(α-methyl styrene), PαMS, and a copolymer of α-methyl styrene/acrylonitrile, PαMSAN. Some of the mixtures showed LCST behaviour and based on this and excess volume measurements, to the extent possible, qualitative conclusions were made concerning the relative strength of the interactions among the various blend pairs. It appears that small amounts of AN or MA in the copolymers apparently increases the strength of interactions relative to those observed in polystyrene blends with MPC, whereas the inclusion of a methyl group in the styrenic repeat unit has the opposite effect. The phase behaviour of MPC with styrene based copolymers appears to be influenced by intrachain repulsion between styrene and comonomer units. MPC was found to undergo thermal and solvent induced crystallization when blends were cast from tetrahydrofuran and toluene solutions, but no crystallinity was observed when methylene chloride was used as the solvent.