Syntheses of Hyperbranched Poly(carbosilarylenes)

New hyperbranched poly(carbosilarylenes) are described that exhibit low glass transition temperatures and high thermal stabilities. The incorporation of Si−O−Si linkages into the branches leads to a polymer of increased flexibility but considerably lower thermal stability. The hyperbranched polymers are prepared via a one-pot hydrosilylation polymerization of aromatic AB3 monomers. The monomers are prepared from commercially available reagents using lithium−halogen exchange reactions followed by treatment with chlorosilanes. The glass transition temperatures of the hyperbranched polymers range from −45 °C for the siloxane-containing polymer to 12 °C for the 1,4-substituted polymer. Number-average molecular weights (GPC) range from 2560 to 5600. The degree of branching in these polymers was determined by quantitative 29Si NMR spectroscopy and found to be very close to the theoretical value of 0.44 for AB3 systems.