Improving the control of styrene polymerization at 60 degrees C using a dialkylated alpha-hydrogenated nitroxide
Abstract
A new dialkylated a-hydrogenated linear nitroxide and the corresponding 1-phenylethyl alkoxyamine were synthesized in two and three steps, respectively. The alkoxyamine was involved in the polymerization of styrene at 60 degrees C, and the in situ concentration of nitroxide was monitored by electron spin resonance spectroscopy. The enhanced characteristics of these new alkylated alkoxyamine and nitroxide (k?d60 = 1.5 x 10-4 s-1 and k?c60 = 5.7 x 104 L mol-1 s-1) yielded a monomer consumption one order of magnitude higher than styrene thermal polymerization. This resulted in well-defined polystyrenes up to 70,000 g mol-1 and the observation of a control occurring through the establishment of the radical persistent effect, that is, ln([M]0/[M]) = t2/3. Experimentally determined kinetic constants were involved in PREDICI modelings to investigate the influence of temperature and initial alkoxyamine concentration on the kinetics as well as on the livingness and the controlled character of the polymerization. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012