Synthesis of semitelechelic POSS-polymethacrylate hybrids by thiol-mediated controlled radical polymerization with unusual thermal behaviors

We have developed an efficient and versatile method for the synthesis of polyhedral oligomeric silsesquioxanes (POSS)-polymethacrylate hybrids, such as POSS-poly(methyl methacrylate) (POSS-PMMA), POSS-poly(ethyl methacrylate) (POSS-PEMA), and POSS-poly(benzyl methacrylate) (POSS-PBzMA) of controllable molecular weights and low polydispersities by thiol-mediated radical polymerization at elevated temperature (100 degrees C). By tuning the reactant concentrations and degree of polymerization of the grafted polymethacrylate chains, POSS content in these hybrid materials could be varied. MALDI-TOF-MS analysis of the hybrid molecule shows that the nanoscale POSS moiety is connected to the end of polymethacrylate chain through the sulfur atom bridge. These hybrid materials were further characterized using various techniques such as FTIR, XRD, NMR, TGA, and DSC. In all synthesized hybrids, the incorporation of POSS moiety at the end of polymethacrylate chain resulted in the decrease of glass transition temperature (T-g) compared to that of neat polymethacrylates of comparable molecular weights. Surprisingly, POSS-PMMA hybrids only with relatively high POSS content (similar to 10 and 16 wt %) showed physical aging behavior as reveled by DSC study. (c) 2007 Wiley Periodicals, Inc.