Distribution of the components between the phases obtained from blends of a styrene-butadiene star-copolymer and polystyrene or polybutadiene

Abstract

With the objective of clarifying the phenomena taking place during the synthesis of high impact polystyrene (HIPS), polymeric mixtures between polystyrene (PS) or polybutadiene (PB) and a star-shaped poly(styrene-butadiene) copolymer (BC) were prepared using ethylbenzene (EB) as a solvent. The molar mass of PS, the BC concentration and the total mass fraction of the PS were varied. The morphology of some of the mixtures or isolated phases was observed by transmission electron microscopy. It was found that the stability of the homopolymer/BC/EB blends increased when their viscosity and affinity between its components were higher. Both, the affinity and the distribution of the components when demixing occurred, were dependent upon the concentration of BC and the relationship between the molar masses of the blocks in BC and each one of the homopolymers investigated. The mixtures PS/BC were stable, except for the case with the high PS molar mass and the highest BC concentration. In this case and also for the PS - rich isolated phase, BC exhibited lamellar microdomains dispersed in a continuous PS-rich phase. The number and diameter of these microdomains were dependent upon the BC concentration in the PS matrix.

Keywords

• demixing
• polymers blends
• star-block copolymer
• polystyrene
• polybutadiene