Makoto Seino

Control of Molecular Weight, Stereochemistry and Higher Order Structure of Siloxane-containing Polymers and Their Functional Design

We describe the precision synthesis schemes of siloxane-containing polymers, i.e., the control of their molecular weight, stereoregularity, and higher-order structures. First, we found a new catalytic dehydrocoupling reaction of water with bis(dimethylsilyl)benzene to give poly(phenylene-disiloxane). Together with this reaction, we applied hetero-condensations to the synthesis of thermally stable poly(arylene-siloxane)s. The dehydrocoupling reaction was applied to the synthesis of syndiotactic poly(methylphenylsiloxane) and poly(silsesquioxane)s, which we also prepared by hydrolysis and deaminative condensation reactions. We discuss the tendency for loop formation to occur in the synthesis of poly(silsesquioxane) by hydrolysis, and provide comments on the design of functionality of the polymers produced. By taking advantage of the low energy barrier to rotation in the silicon-oxygen bond, we designed selective oxygen-permeable membrane materials and liquid crystalline materials. The low surface free energy of siloxane-containing systems allows surface modification of a blend film and the design of holographic grating materials.

Synthesis, end-functionalization and characterization of hyperbranched polysiloxysilanes from AB3 type monomer

Hyperbranched polysiloxysilanes (HBPSs), with a variety of terminal functional groups (vinyl, epoxy, carboxyl and hydroxyl), were synthesized by the self-polymerization of an AB3 type monomer of tris(dimethylvinylsiloxy) silane, with subsequent end-functionalizations, such as epoxidation and radical addition reaction, respectively. The ratio of the α- and β-addition linkages in the HBPS polymerized by hydrosilylation of the AB3 monomer was found to be approximately 1 to 3. The thermal stability and solubility were affected by the terminal functional groups.

High Performance Siloxane-Containing Polymers

Catalytic cross-dehydrocoupling polymerization of silane and water, and deaminative polymerisation between silanol and aminosilane are used to synthesize a variety of silicon-containing polymers with controlled structure.n-Hexylamine-2-ethylhexoate was used to catalyze silanol condensation. Among transition metal derivatives investigated, Pd2(dba)3is the most active catalyst for the dehydrocoupling polymerisation, and deaminative polymerisation proceeded smoothly by heating. Optically active siloxane materials of branched structure were obtained from(S,S)-1,3-dimethyl-1,3-diphenyldisiloxanediol and(S,S)-1,5-di(1-naphthyl)-1,5-diphenyl-1,5-divinyl-3-methyltrisiloxane(>99%ee)as optically active building blocks.

Polymers with cyclotetrasiloxane moiety via cross-dehydrocoupling polymerization of 1,5-dihydro-1,5-dimethyl-3,3,7,7-tetraphenylcyclotetrasiloxane

Catalytic cross-dehydrocoupling polymerization reactions of 1,5-dihydro-1,5-dimethyl-3,3,7,7-tetraphenylcyclotetrasiloxane with water and diols were investigated. Chlorotris(triphenylphosphine)rhodium(I) was an efficient catalyst for the polymerization and afforded polymers with moderate molecular weight. Chemical structures and thermal properties of polymers were characterized by NMR, IR and TGA.