Synthesis of cross-linked comb-type polysiloxane for polymer electrolyte membranes

Abstract

Hydrosilylation reaction of 2.4.6.8-tetrahydro-2.4.6.8-tetramethylcyclotetrasiloxane with allyl acetoacetate and vinyltriethoxysilane at 1:3:1 ratio of initial compounds in the presence of Karstedt’s catalyst (Pt2[(VinSiMe2)2O]3), platinum hydrochloric acid (0.1 M solution in THF) and platinum on the carbon have been studied and D4R,R’ type methylorganocyclotetrasiloxane has been obtained. Ring-opening co-polymerization reactions of methylorganocyclotetrasiloxane and hexamethyldisiloxane, in the presence of catalytic amount of powder-like potassium hydroxide, have been carried out and linear methylsiloxane oligomer with regular arrangement of propyl acetoacetate and triethoxysilane groups in the side chain has been obtained. The synthesized methylorganocyclotetrasiloxane and oligomers were studied by FTIR, 1H, 13C, 29Si NMR spectroscopy. Comb-type oligomers were characterized by gel-permeation chromatography, wide- angle X-ray and differential scanning calorimetric methods. Via sol-gel processes of doped with lithium trifluoromethylsulfonate (triflate) or lithium bis- (trifluoromethylsulfonyl)imide oligomer systems solid polymer electrolyte membranes have been obtained. The dependence of ionic conductivity as a function of temperature and salt concentration has been studied. The electrical conductivity of these materials at room temperature belongs to the range of 7x10-8 to 4x10-6 S cm-1 and depends on the structures of grafted anion receptors and the polymer backbones.