Exploring amino acid‐tethered polymethacrylates as CO₂‐sensitive macromolecules: A concealed property.

Abstract

Carbon dioxide (CO2)-responsive polymers have been gaining considerable interest because of their reactions with CO2, giving rise to gas-switchable properties, which can easily be reversed by mild heating or purging with inert gases. Herein, the synthesis of a series of side-chain amino acids (alanine, leucine, isoleucine, phenylalanine, tryptophan) appending poly(meth)acrylates carrying primary amine (NH2) groups via reversible addition-fragmentation chain transfer (RAFT) polymerization method was reported. It was found that alanine, leucine, isoleucine containing polymers displayed solubility–insolubility transition behavior and their associated property changes (solution transmittance, electrical conductivity, pH, zeta potential, and hydrodynamic diameter) in water upon alternate bubbling of CO2/N2 at room temperature. Among the three CO2-sensitive polymers only leucine based macromolecule was further chain extended with a thermoresponsive motif, di(ethylene glycol) methyl ether methacrylate (DEGMMA), via RAFT polymerization. CO2-tunable lower critical solution temperature and self-assembling behavior of the diblock copolymer was carefully examined by UV–vis, 1H NMR spectroscopy, dynamic light scattering (DLS), and field emission-scanning electron microscopy (FE-SEM) to establish dual thermo and gas-tunable flip–flop micellizaion from the as-synthesized block copolymer. Formation of polyammonium methacrylate bearing bicarbonate as counter anion is responsible for pendant primary amine containing polymer induced CO2-responsiveness. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2794–2803