Synthesis of Branched Polysiloxanes with Controlled Branching and Functionalization by Anionic Ring-Opening Polymerization

Functionalized branched polysiloxanes with star-branched, comb-branched and dendritic-branched topologies were synthesized. The branched macromolecules were generated by coupling of reactive blocks using a grafting technique (ACS Polym. Prepr. 2001, 42, 227; ACS Symp. Ser. 2003, 838, Chapter 2). The living anionic ring-opening polymerization (ROP) of vinyl-substituted cyclotrisiloxanes (ViMeSiO)3, V3, and, VD2, and the copolymerization of these monomers with hexamethylcyclotrisiloxane, D3, was explored to obtain reactive blocks. Termination of the living polymer, having a lithium silanolate end group, on a reactive core containing SiCl groups led to the grafting of living polysiloxane on the core. Transformation of vinyl groups in the polymer into the reactive SiCl groups by hydrosilylation with Me2HSiCl made possible the grafting of a successive generation of branches. The reactive blocks of high and low density of the precursor vinyl group were obtained by the polymerization of monomers V3 and VD2, resp...