MICROSTRUCTURE EFFECT IN THE COUPLING REACTIONS OF POLYMERIC ORGANOLITHIUM COMPOUNDS USING CHLOROSILANES

The most important variable affecting the yield in the coupling reacti ons of polymeric organolithium compounds with chlorosilane compounds h as been investigated through size-exclusion chromatographic (SEC) anal ysis. The coupling reaction of poly(styryl)lithium with dichlorodimeth ylsilane as a silane-coupling agent provided 44 wt % of the coupling y ield. The coupling yield, depending on the chain end reactivity of act ive polymers, was not greatly affected. The addition of a Lewis base s uch as N,N,N',N'-tetramethylethylenediamine (TMEDA) even after complet e polymerization of the dienes in hydrocarbon seems to affect the coup ling reaction, resulting in decreasing the yield. The 1,2- or 3,4-ench ain contents in the polydiene backbones affected the reduction of the linking efficiency in the coupling of the poly(dienyl)lithiums with ch lorosilanes as the linking agent. The linking yields of the active pol ymers including over 75 mol % of 1,2- or 3,4-enchainment on the polydi ene segment were below 20 wt %. The linking yields exhibited a depende nce not only on the steric requirement of the chain end, but also the microstructure of the polydiene segment. (C) 1998 John Wiley & Sons, I nc.