No abstract

Various commercially available thiols react photochemically with tetravinylsilane to give the corresponding tetrasubstituted thioether compounds. The reactions are conducted in air using typical borosilicate glassware. Yields range from 64 to 100%, and purification steps, if necessary, involve simple precipitation or extraction steps. Thiol addition occurs predominantly to give the anti-Markovnikov product; amounts of Markovnikov addition range from 1 to 5%.

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.

The application of thiol-ene chemistry to the synthesis of new carbosilane-thioether dendrimers is presented in this work. The dendrimers are prepared in a divergent fashion starting with tetravinylsilane as a core, followed by a succession of alternating thiol-ene and Grignard reactions. Vinyl-terminated dendrimers up to the fifth generation were isolated in excellent yields (78-94%). Products were characterized by multinuclear NMR spectroscopy, dynamic light scattering, gel permeation chromatography, and MALDI-TOF mass spectrometry.

Coordination between Ag-loaded polystyrene-co-dendrimer microspheres enables the construction of large-area crack-free photonic crystal films and invisible patterned photonic displays.