Crystallization-induced phase separation in mixtures of model linear and short-chain branched polyethylenes

Abstract

Abstract The possibility of cocrystallization is investigated in a model system of linear and short-chain branched polyethylene. Both components have low molecular weight and narrow molecular weight distribution; the branched component, hydrogenated polybutadiene (HBD), contains one ethyl branch per 60–70 backbone carbon atoms. Cocrystallization was not observed even for the most rapid cooling conditions attainable, despite the essentially identical unit cells of the two materials. A combination of microscopy and scattering techniques was used to demonstrate that the HBD and linear polyethylene (LPE) crystallize into separate lamellar stacks. The rapid growth rate of the LPE creates volume-filling spherulites which trap the HBD in micron-size inclusions, within which it subsequently crystallizes on further cooling.