Design of smart polyacrylates showing thermo-, pH-, and CO2-responsive features

Abstract

A novel acrylate monomer 2-((3-(isopropylamino)-3-oxopropyl)(methyl)amino)ethyl acrylate (IMA) was synthesized by facile sequential two-step reactions and polymerized using reversible addition–fragmentation chain transfer (RAFT) polymerization to yield a thermo-, pH- and CO₂-responsive homopolymer PIMA with a well-defined structure. PIMA showed a lower critical solution temperature (LCST) close to body temperature, and the influence of the degree of polymerization (DP), polymer concentration, salt concentration and substituents on the LCST was investigated. Due to the presence of tertiary amino groups in the side chains, the thermoresponsive phase transition of PIMA was tunable by solution pH and bubbling CO₂/N₂. The LCST increased with the decrease of pH, and the solubility of PIMA (at a temperature above the LCST) could be reversibly switched back by bubbling CO₂/N₂.