Flocculation studies of non-aqueous poly(methyl methacrylate) dispersions. II. Stabilization with the diblock copolymer poly (styrene-b-[ethylene-co-propylene])

Well defined non-aqueous dispersions of poly(methyl methacrylate) stabilized by the diblock copolymer poly(styrene-b-[ethylene-co-propylene]) have been studied with a dispersion medium consisting of a binary liquid mixture of n-heptane and n-propanol. Flocculation was induced by adding n-propanol at constant temperature, to find the critical flocculation volume, and by cooling, to find the critical flocculation temperature. Theta conditions for ethylene-propylene copolymer in the same binary liquid mixture were determined using samples obtained by hydrogenating polyisoprene standards. These dispersions just retained stability at theta conditions, with flocculation occurring when the dispersion medium was slightly worse than a theta system for the stabilizing ethylene-propylene chains.