Preparation of poly(N-isopropylmethacrylamide) latexes kinetic studies andcharacterization

Thermosensitive crosslinked polymer latexes have been synthesized by precip itation polymerization of N-isopropylmethacrylamied (NIPMAM) as a main mono mer, methylene bis-acrylamide (MBA) as a crosslinker, and potassium persulf ate (KPS) as the initiator. Polymerizations kinetics were first investigate d by studying both the influence of crosslinker (MBA) and initiator (KPS) c oncentrations and temperature effects on the polymerization conversion, the particle size, and water-soluble polymer (WSP) as a function of time. Part icle size analysis by Scanning Electron Microscopy (SEM) showed that a shor t nucleation step afforded the synthesis of highly monodispersed latexes. I n addition, a strong dependence of WSP formation on MBA and KPS concentrati on and polymerization temperature was found, as well. Comparison of particl e size by SEM and quasielastic light scattering clearly evidenced the drama tic effect of temperature on particle size. Lower critical solubility tempe ratures (LCST) of latexes were determined and compared. Finally, based on t hese results, the mechanism of particle formation in this polymerization pr ocess is discussed. (C) 1999 John Wiley & Sons, Inc.