Efficient synthesis of ω-(p-vinylbenzyl)polystyrene by direct functionalization of poly(styryl)lithium with p-vinylbenzyl chloride in hydrocarbon solvent with lithium 2,3-dimethyl-3-pentoxide

The direct functionalization of poly(styryl)lithium (M _n≈ 2000 g/mol) with p-vinylbenzyl chloride (VBC) has been investigated in hydrocarbon solvent. With a 9-fold excess of VBC and normal addition, the predominant product (55% yield) was the corresponding head-to-head dimer; the macromonomer was formed in only 20% yield as determined by ¹H NMR analysis. MALDI-TOF MS analysis of the products showed that the other major side reaction products resulted from addition of PSLi to the vinyl group of VBC. However, in the presence of excess lithium halides (LiCl, LiBr) the amount of dimer formation was reduced (30%), but the yield of macromonomer was increased only slightly (27%). The principal impurity was the corresponding nonfunctional polystyrene attributed to hydrogen abstraction from VBC by PSLi. A high yield (≥98%) of ω-(p-vinylbenzyl)-polystyrene macromonomer was obtained when the functionalization was effected in the presence of 10 equiv of lithium 2,3-dimethyl-3-pentoxide. No dimer formation was observed by SEC analysis, but the presence of a small amount (≤2%) of nonfunctional polystyrene was detected by MALDI-TOF MS analysis of the product.