Polymerization of Acrylamide in Aqueous Solution of Poly(N‐isopropylacrylamide) at Lower Critical Solution Temperature

Abstract

Acrylamide (AAm) was found to polymerize in a solution of poly(N-isopropylacrylamide) (PNIPAAm) in water at around its lower critical solution temperature (LCST) (328C) without any initiators. This phenomenon was specifically observed in aqueous solutions of the polymers having LCST such as PNIPAAm and poly(methylvinylether) (PMVE). AAm polymerized only when PNIPAAm and AAm were dissolved in water below LCST of PNIPAAm and then the solution was warmed up to the polymerization temperature (408C). On the other hand, the polymerization of AAm did not proceed when AAm was added into aqueous PNIPAAm solution during and after the phase separation above 328C. Furthermore the polymerizability of AAm was remarkably affected by the concentration and molecular weight of the PNIPAAm additives. Under the condition of lower PNIPAAm concentration (0.30 mol/L), the increase in the molecular weight of PNIPAAm considerably increased the molecular weight of the resulting PAAm but decreased the yield of PAAm. Under the condition of higher PNIPAAm concentration (0.60 mol/L) the polymerizability was not so affected by the molecular weight of PNIPAAm, while the molecular weight of PAAm formed by using higher molecular weight PNIPAAm was higher than those of PAAm formed by using lower molecular weight PNIPAAm. Moreover, the molecular weight of PAAm formed by the PNIPAAm induced polymerization of AAm was much higher than that of the polymer obtained by the radical polymerization using AIBN in THF or VA-061 in water.

Synthesis and catalytic activity of the thermoresponsive polymers having pyrrolidine side chains as base functionalities

“…In our continuous study, we have found that acrylamide (AAm) was polymerized in a solution of poly( N ‐isopropylacrylamide) (PNIPAAm) in water around its LCST(32°C) without any initiators 17. The mechanism of this polymerization is not always clear at presence, but the solution conditions of PNIPAAm in water at around its LCST is one of most important factors to induce the polymerization.…”

Thermoresponsive and Redox Behaviors of Poly(N-isopropylacrylamide)-Based Block Copolymers Having TEMPO Groups as Their Side Chains

“…This potential shift indicates that the TEMPO moieties are surrounded by the PNIPAAm chains and placed on relatively hydrophobic environment during the phase transition at LCST. We have also observed the concentration behavior of organic substrates into the hydrophobic field generated by PNIPAAm during the phase transition [12,21]. These phenomena encourage us to perform the TEMPO-mediated oxidation of organic compounds in the thermoresponsive polymer field.…”

Preparation of Thermoresponsive Polymer-Modified Electrodes Having a TEMPO Moiety

“…We have also observed the concentration behaviour of organic substrates into the hydrophobic field generated by PNIPAAm during the phase transition in non-electrochemical system. 26 This phenomenon encourages us to perform the electrochemical reactions in the polymer field on the electrode surface. Organic substrates are concentrated on the electrode surface by thermoresponsive shrinking of the grafted PNIPAAm chains, and it possibly enhances the efficiency of the electrochemical reactions mediated by the TEMPO moieties.…”