Partitioning of the components into two-demixed-macrophases from a solution blend emulating high impact polystyrene close to the phase inversion region

Abstract

Blends of a butadiene rich-tapered diblock copolymer (DC) with polystyrene (PS) and/or polybutadiene (PB) in ethylbenzene (EB) were investigated to better understand the phenomena occurring during the synthesis of high impact polystyrene (HIPS). For the first time, the apparent partitioning of components between the demixed phases of quaternary blends PS/PB/DC/EB was determined, involving variations of DC concentration, PS molar mass, simulated conversion of styrene and temperature. The new methodology combines FTIR, solvent extraction, TLC and mass balances and verifies important results by TEM and SEC. During demixing, a molecular fractionation occurs which depends on the DC composition distribution, the ratio between the molar masses of each of the copolymer blocks and the respective homopolymers and the viscosity ratio between the continuous and dispersed phases. The affinity between the low molar mass PS and the PS block in DC favors the stabilization of PS domains in the PB-rich phase.