Effects of Main-chain and Chain-ends on the Organogelation of Stearoyl Appended Pendant Valine Based Polymers

Abstract

In this work, we investigated the effect of hydrophobic interactions between the polymeric backbone and chain-end groups on the self-assembly pathway of stearoyl appended side-chain valine (Val)-based poly(methacrylate/acrylate) homopolymers in different organic hydrocarbons. Gelation studies conducted revealed that while polymers with polyacrylate as backbone induces gelation in several organic hydrocarbons, polymers with polymethacrylate in the main-chain significantly hinders macroscopic gelation. Morphology of the organogels was analysed by field emission scanning electron microscopy (FESEM), and mechanical strengths of the organogels were determined by rheological measurements. Reversible addition-fragmentation chain transfer (RAFT) polymerization chain transfer agents (CTA)s, [R1-S-C=(S)-S-R2] with different -R1 and -R2 groups, have been employed to study the effect of structural variation at the chain-end on macroscopic assembly mechanism. We found that the additional interactions between terminal groups via hydrogen-bonding or π-π stacking interactions or both help to build up the self-assembly pathway and thereby produces mechanically stable organogels.