Ultrasonic Polymerization of N-Isopropylacrylamide below and above Critical Temperature

概要

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Poly(N-isopropylacrylamide) is a well-known thermosensitive polymer exhibiting a phase transition at 32 °C. Here, ultrasonic polymerization of the monomer, N-isopropylacrylamide, in an aqueous solution is reported as a novel reaction. Ultrasound irradiation of an N-isopropylacrylamide aqueous solution for approximately 30 min produced the polymer. The yield and molecular weight ($M_{\text{w}}$) of the polymer were measured for various temperatures and monomer concentrations. At 15 °C (below the critical temperature), the reaction yield did not increase after 1 h. At 33 °C (above the critical temperature), however, polymerization continued even 6 h after sonication, producing twice the yield obtained at 15 °C. The $M_{\text{w}}$ of the polymer obtained at 33 °C was $5 \times 10^{4}$ g/mol, approximately five times that at 15 °C.
2010-07-25