Microstructure and mechanical properties of amphiphilic tetrablock copolymer elastomers via RAFT miniemulsion polymerization: influence of poly[styrene-alt-(maleic anhydride)] segments

Abstract

A series of well-defined poly[styrene-alt-(maleic anhydride)]-block-polystyrene-block-poly(n-butyl acrylate)-block-polystyrene tetrablock copolymers (SMA-PSt-PnBA-PSt) were synthesized via RAFT miniemulsion polymerization. The precursors were amphiphilic macroRAFT agents (poly[styrene-alt-(maleic anhydride)]-RAFT, SMA-RAFT) with different chain lengths. The structure of the copolymers was characterized by ¹H NMR, GPC, and DSC analysis. The influence of the hydrophilic SMA block on the microphase separation and mechanical properties of the copolymers was illustrated by TEM observation and tensile tests. The results showed that the increasing fractions of SMA in the tetrablock copolymers led to sea-island or wormlike morphology in the elastomeric matrix and higher T_g, simultaneously increasing the ultimate tensile strength and lowering the elongation at break. With its moderate amount of compatibility groups and typical elasticity, the synthesized tetrablock copolymer SMA_5k-PSt_20k-PnBA_40k-PSt_20k could be a potential candidate for toughness modification.