Synthesis of poly(vinyl acetate)-graft-polystyrene and its compatibilizing effect on PS/PVAc blends

Poly(vinyl acetate)-TEMPO macroinitiators were synthesized by polymerization of vinyl acetate with benzoyl peroxide followed by termination of the radicals using 2,2,6,6,-tetramethyl-1-piperidinyloxy (TEMPO). Copolymerization of styrene was performed in the presence of the macroinitiator. Due to chain transfer to polymer reactions during the bulk polymerization of vinyl acetate, the copolymerization produced graft copolymers of poly(vinyl acetate) (PVAc) and polystyrene (PS) instead of the corresponding block copolymers. The PVAc-g-PS copolymers had a phase-separated morphology, and the phase separation was realized more completely in the copolymer with the highest VAc content (PS124TP115). PS124TP115 enhanced elongation at break of PVAc/PS blend significantly. The size of the PVAc domains in PS/PVAc/PVAc-g-PS blends decreased and adhesion strength measured by the peel test for hot pressed PS and PVAc sheets with the copolymer inserted in between increased in the order of PS124TP115≫PS145TP110≈PS144TP096≈PS162TP089, indicating that PVAc-g-PS copolymers having similar content of the components were more effective in compatibilizing the PS/PVAc blends.