Chemical modification of poly(methylphenylsiloxane)

Abstract

Poly(methylphenylsiloxane) (PMPS) with a narrow molecular weight distribution (MWD) was prepared by anionic polymerization, and ring-functionalized using procedures optimized to minimize chain degradation. The products were characterized by NMR and IR spectroscopy, and the MWD of the polymers was analyzed by size exclusion chromatography, to monitor polymer degradation and crosslinking during the functionalization reactions. Electrophilic substitution was used to introduce nitro and bromo groups on the phenyl ring of the polymer. Nitration with fuming nitric acid yielded up to 8 mole % substitution with some chain degradation. Bromination was achieved with bromine in the presence of either pyridine or triethylamine. A substitution level of up to 14 mole % and a small increase in the polydispersity index (Mw/Mn) were obtained with triethylamine. Hydroxyethyl functionalities were obtained by lithiation of the brominated PMPS via metal-halogen exchange, and reaction with ethylene oxide. A polymer with 3 mole % hydroxyethyl functionalities was obtained with moderate chain degradation. A substitution level of 6 mole % could be achieved under different conditions, but with more extensive chain degradation. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 653–664, 1999