Tuning the Viscoelastic Properties of Poly(n-butyl acrylate) Ionomer Networks through the Use of Ion-Pair Comonomers

Abstract

An organic ion-pair comonomer (IPC) based on anionic and cationic styrenic monomers was synthesized and copolymerized with n-butyl acrylate (BA) by reversible addition–fragmentation chain transfer (RAFT) polymerization to generate physically cross-linked polyampholyte ionomer networks. Evidence of microphase separation of the ion pairs to produce ion-rich domains was found by rheological and atomic force microscopy measurements. Comparison of these polymers to chemically similar cationic and anionic ionomers with only one type of ion covalently bound to the polymer backbone demonstrated that the connectivity of the ions to the polymer backbone had a strong effect on the viscoelastic properties. Characterization of the corresponding polyelectrolytes showed a ca. 125 °C increase in the glass transition temperature (Tg) from the cationic to the polyampholytic polyelectrolyte. In the ionomers, this elevated Tg allowed the vitrification of the ion-rich domains at ambient temperatures in the polyampholyte netwo...