Regular comb polystyrenes and graft polyisoprene/polystyrene copolymers with double branches ("Centipedes"). Quality of (1,3-phenylene)bis(3-methyl-1-phenylpentylidene)dilithium initiator in the presence of polar additives

The synthesis of regularly spaced comb polystyrenes and graft polyisoprene/polystyrene copolymers with two branches at each junction point (centipedes) is presented. The synthetic approach involves the selective replacement of two chlorines of SiCl₄ by polystyrene (PS) followed by step-growth polymerization of the produced (PS)₂SiCl₂ with α,ω-dilithium PS or 1,4 polyisoprene (PI). The polydispersity indices of the reaction products, PS-g-PS₂ (homocentipedes) and PI-g-PS₂ (cocentipedes), varied between 2.0 and 3.0 but was reduced to 1.2-1.3 by fractionation. The quality of (1,3-phenylene)-bis(3-methyl-1-phenylpentylidene)dilithium initiator (DLI), used for the synthesis of the dianion, in the presence of polar additives (THF, Et₃N, and s-BuOLi), was evaluated.