A New Methodology for the Synthesis of Star Polymers Utilizing the Reaction of Living Polymers with Alkoxysilyl-Functionalized Polymers

A novel method for linking polymeric organolithium compounds to form heteroarm (miktoarm) star-branched polymers has been demonstrated. After functionalization of a polymeric organolithium compound with excess multifunctional chlorosilane linking agent, the resulting polymeric chlorosilyl groups were converted to methoxysilyl groups with anhydrous methanol followed by precipitation into methanol. This procedure removed excess, nonvolatile, linking agent required to prevent linking reactions. Polystyrene- b -oligo(butadienyl)lithium (PS- b -oligoBD) was functionalized with excess 1,2-bis(dichloromethylsilyl)ethane in benzene with added triethylamine to minimize linking reactions during conversion of chlorosilyl to methoxysilyl groups. Quantitative conversion and complete removal of excess linking agent were demonstrated by SEC, 1 H NMR, 13 C NMR, and 29 Si NMR analyses. MALDI−TOF mass spectral analysis of the methoxysilyl-functionalized PS- b -oligoBD was consistent with the proposed structure and indicated the absence of side reaction products. A 4-arm, star-branched polystyrene prepared by treating methoxysilyl-functionalized PS- b -oligoBD with excess PS- b -oligoBDLi was essentially indistinguishable from an analogous polymer prepared using only 1,2-bis(dichloromethylsilyl)ethane. While the method has been demonstrated for synthesis of a 4-arm star, its use will have greatest benefit for the synthesis of higher order, multibranched, miktoarm star materials.