Ultrasonic Polymerization of N-Isopropylacrylamide below and above Critical Temperature

Abstract

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 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 w of the polymer obtained at 33 C was 5 Â 10 4 g/mol, approximately five times that at 15 C. #

Role of External Field in Polymerization: Mechanism and Kinetics

“…Teo et al 885 and Yanagida et al 886 independently reported the preparation of PNIPAM in the absence of extra chemical initiator using ultrasound irradiation at different ultrasonic frequencies (i.e., 20 kHz and 1 MHz, respectively), but the polymerization kinetics showed diametrically opposite results and have been interpreted in two different ways. Teo et al showed that the polymerization rate at 20 °C was higher than that at 45 °C, a temperature above the LCST of PNIPAM.…”

Effect of ultrasonication on polymerization of silicic acid in geothermal water

“…When ultrasound is irradiated onto a liquid, chemical reactions occur by cavitation. The synthesis, 8) decomposition, [9][10][11][12][13][14][15] and polymerization 16) of organic materials in solutions have been conducted. However, the effect of ultrasonic irradiation on silicic acid solution has never been reported to the best of our knowledge.…”