Synthesis of Poly(N-isopropylacrylamide) in Supercritical Carbon Dioxide and Properties of Aqueous Solutions of the Obtained Polymers

Poly(N-isopropylacrylamide) has been synthesized for the first time by reversible addition-fragmentation chain transfer polymerization in supercritical carbon dioxide. It has been shown that the molecular weight distribution of the polymer is narrower and its average molecular weights are lower than those of poly(N-isopropylacrylamide) synthesized in supercritical СО₂ (scСО₂) according to the conventional radical mechanism. Both polymers are branched and contain a minor proportion of the gel fraction. The form factors determined by light scattering are 1.35 (conventional polymerization) and 1.11 (reversible addition-fragmentation chain transfer polymerization), which is typical for branched and hyperbranched polymers, respectively. Aqueous solutions of the polymers are thermoresponsive and characterized by a cloud point of 30–31°С.