Starlike polymeric architectures by atom transfer radical polymerization: Templates for the production of low dielectric constant thin films

The synthesis of novel poly(methyl methacrylate)s with starlike architectur es by controlled radical polymerization starting from dendritic 2-, 4-, 6-, and l2-arm multifunctional initiators is described. The more highly functi onalized initiators were obtained by coupling a bromo-functionalized bis(hy droxymethyl)propionic acid (bis-MPA) first generation dendron to hydroxyl-f unctionalized precursors. The controlled free radical character of the atom transfer radical polymerization is supported by the remarkably low polydis persities of the polymers and the close correspondence between the calculat ed and measured molecular weights. NMR studies on the polymers were consist ent with initiation occurring from all initiator arms for the 2-, 4-, and 6 -arm derivatives. Initial studies on deuterated polymers derived from la-ar m initiator suggest that in some cases initiation was not quantitative. In addition, starlike random copolymers of methyl methacrylate containing vary ing amounts of hydroxyethyl methacrylate with slightly higher polydispersit ies have been synthesized. Preliminary results show that these copolymers c an be used to produce nanophase-separated inorganic/organic hybrids by temp lating vitrification of methylsilsesquioxane (MSSQ) and nanoporous thin fil ms after subsequent thermal degradation of the organic polymer. Transmissio n electron microscopy confirms a nanoporous morphology of the thin films, a nd a decrease of the dielectric constant is observed.