FREE-RADICAL POLYMERIZATION OF NONLINEAR-OPTICAL SIDE-CHAIN METHACRYLATE COPOLYMERS IN DIMETHYLSULFOXIDE - AN EXPERIMENTAL-DESIGN

Copolymers prepared by free radical initiation of various ratios of tw o comonomers, hyl[4-[2-(4-nitrophenyl)ethenyl]phenyl]amino]ethyl 2-pro penoic acid ester (C2ANS) and methyl methacrylate (MMA) are used in th e fabrication of nonlinear optical (NLO) devices at Hoechst Celanese. Since the production of these polymers is on the kilogram scale, it wa s important to optimize the reaction condition to maximize the convers ion to high molecular weight product. A set of 22 statistically (D-opt imal) designed experiments was run where the variables were temperatur e (55-75 degrees C), ratio of C2ANS to MMA, the 2,2'-azobis[2-methyl-p ropanenitrile] (AIBN) concentration, and the level of a coupling agent . Initiator concentration, the ratio squared of the monomers, and the temperature are the most important factors for the polymer percent and the polymer yield. The concentration of the coupling agent, the ratio squared of the monomers, and the interaction of the ratio with the co upling agent are the key factors for the polymer molecular weight. Thr ee-dimensional plots of these measured values show that the highest mo lecular weight polymer, with a 90% or better yield, is obtained at a t emperature of 64-68 degrees C for a ratio of 45-46:55-56 C2ANS:MMA usi ng 1 mol% AIBN.