Synthesis of thermoresponsive phenyl- and naphthyl-terminated poly(NIPAM) derivatives using RAFT and their complexation with cyclobis(paraquat-p-phenylene) derivatives in water

Abstract

A series of poly(N-isopropylacrylamide)s (poly(NIPAM)s) have been synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization from a functionalized chain transfer agent (CTA) bearing either dialkoxynaphthalene or dialkoxyphenylene moieties. After demonstrating the controlled character of the RAFT polymerization in the presence of these CTAs, well-defined functionalized poly(NIPAM)s with low PDIs and similar molecular weights were selected and subjected to lower critical solution temperature (LCST) measurements using UV-vis spectroscopy. We have investigated the complexation of the polymers with the tetracationic cyclophane cyclobis(paraquat-p-phenylene) (CBPQT⁴⁺) and specifically the role the counter anion (Cl⁻, Br⁻, I⁻) of the cyclophane has on the LCST. Moreover, we have shown that the addition of a competing end-functionalized naphthalene poly(NIPAM) guest to a (CBPQT⁴⁺)–end-functionalized phenylene poly(NIPAM) complex results in the dethreading of the original architecture.