PREPARATION OF POLY(METHYL METHACRYLATE) AND COPOLYMERS HAVING ENHANCED THERMAL STABILITIES USING SUCROSE-BASED COMONOMERS AND ADDITIVES

A series of methyl methacrylate polymers have been prepared containing sucrose-based crosslinkers and additives. Thermogravimetry and long-t erm aging studies at 200-degrees-C show that sucrose-based alkyl and a llyl ethers provide unprecedented thermal stability to linear, as well as crosslinked, poly(methyl methacrylate) or PMMA. Linear PMMA and PM MA crosslinked with trimethylolpropane trimethacrylate (TMPTMA) both d egrade at 284-degrees-C. PMMA containing octa-O-crotylsucrose (1 mol % ) degraded at 322-degrees-C. Depending on concentration, PMMA containi ng octa-O-allylsucrose (0.1-1.0 mol% and higher) degraded between 334 and 354-degrees-C, and PMMA containing -trimethacryloyl-2,3,3',4,4'-pe nta-O-methylsucrose (0.1-1.0 mol %) degraded between 309 and 320-degre es-C. PMMA containing (1 mol % each) sucrose-based esters, ester-ether derivatives, all degraded at or below the degradation temperature of pure PMMA. Long-term air aging studies revealed that PMMA containing p enta-O-methylsucrose trimethacrylate, octa-O-allylsucrose, and octa-O- crotylsucrose did not flow or sag after heating for 24 h at 200-degree s-C, but the polymers did show yellowing. While linear and crosslinked samples of PMMA containing compounds other than sucrose ethers lost m ore than 50% of their original weight within 15 h at 200-degrees-C, PM MA containing sucrose-based ethers lost about 8 and 20% of their origi nal weight after 1 and 8.5 days, respectively. Herein we propose a uni que mechanism by which saccharide ethers may be imparting this unprece dented thermal stabilization to PMMA. While tertiary hydrogens alpha t o oxygens in saccharide ethers are stable to chain transfer during nor mal polymerization temperatures, they readily chain transfer at 200-de grees-C where PMMA is unstable. Chain transfer of these hydrogens is f ollowed by fragmentation to produce alkyl, allyl or crotyl radicals, w hich combine with the macroradicals and terminate depropagation. (C) 1 995 John Wiley & Sons, Inc.