Siloxanes synthesis

Dendritic polymers, fullerene, 12 252 Dendritic salt, 22 805 Dendritic siloxanes, synthesis of, 22 554 Dendrobine, 2 102... 

Linear polarization, and NLO properties, 12, 102 Linear polymers, siloxanes, synthesis, 3, 660 Linkage isomerism, for photochromic behavior, 1, 245 Linked cages, metallacarboranes, 3, 245 Linkers, traceless, chromium carbonyls as, 5, 251 Lipids, in bioorganometallic chemistry, 1, 904 Liquefied noble gases, in low-temperature infrared studies, 1, 264... 

The traditional approach used in poly(imide-siloxane) synthesis is the reaction of aminopropyl-terminated dimethylsiloxane oligomers with aromatic dianhydrides and additional diamines (9-13). Typically, subambient temperatures and dipolar aprotic solvents are used. The resulting high-molecular-weight polyamic acid solution can be heated to effect imidization and solvent evaporation. This procedure is analogous to the synthetic method used to prepare conventional polyimides for films and coatings. 

A Facile Synthetic Route to Phosphazene Base Catalysts and Their Use in Siloxane Synthesis... 

Phosphazene Base Catalysts and their Use in Siloxane Synthesis 629... 

Through steric hindrance and conjugative effects, these ionic phosphonium salts are very stable to hydrolysis. This, coupled with the lipophilic nature of the cation, results in a very soft, loosely bound ion pair, making materials of this type suitable for use as catalysts in anionic polymerization [8 - 13]. Phosphazene bases have been found to be suitable catalysts for the anionic polymerization of cyclic siloxanes, with very fast polymerization rates observed. In many cases, both thermodynamic and kinetic equilibrium can be achieved in minutes, several orders of magnitude faster than that seen with traditional catalysts used in cyclosiloxane polymerization. Exploiting catalysts of this type on an industrial scale for siloxane polymerization processes has been prevented because of the cost and availability of the pho hazene bases. This p r describes a facile route to materials of this type and their applicability to siloxane synthesis [14]. 

The great variety of properties is obtained by the use of different substituting groups in the siloxane synthesis, variation of the molecular weight, the extent of copolymerization with other polymers (alkyd resins, polyesters), and the addition of additives, pigments, fillers. 

Zhou, Y, Shimizu, K., Cha, J.N., Stucky G.D., and Morse, D.E. (1999) Efficient catalysis of poly-siloxane synthesis by silicatein a requires specific hydroxy and imidazole functionalities. Angew Chem. Int. Ed., 38, 779-782. 

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