Synthesis of a difunctional organolithium compound as initiator for the polymerization of styrene‐butadiene/isoprene‐styrene triblock copolymer

Abstract

A difunctional organolithium compound was prepared by the addition of butyllithium (BuLi) to 1,4-bis(4-methyl-1-phenylethenyl)benzene (MPEB). The effects of the solvent, polar modifier (THF), butyl lithium structure, and reaction time on the formation of the difunctional organolithium compound were studied. Results showed that toluene as solvent was in favor of the addition reaction over cycohexane, in the absence of the polar modifier. However, cycohexane was a better option as solvent for the addition reaction, when polar modifier was employed. A small amount of polar modifier could efficiently accelerate the reaction rate and have no significant effect on the structure of the polydiene, which was initiated by the polar modifier containing organolithium compound. Results also showed that isobutyl lithium was more active in the addition reaction than n-butyl lithium, because of inductive effect. The optimum molar ratio of THF/Liϩ was determined as 4. The THF containing difunctional organolithium cyclohexane solution was sequentially used in the step-wise polymerization of triblock thermoplastic copolymer SIBS. The so-prepared SIBS shared the similar phase separation structure with SBS and exhibited excellent mechanic properties. As the content of the central polyisoprene block increases, the tensile strength of the copolymer is decreased, and the elongation at break is increased. The glass transition temperature T g of the central block was correlated with its content as T g ϭ 0.33 ϫ Ϫ62.81, where ϫ is the wt % of the central block, based on the triblock copolymer.

Influence of (1,3‐phenylene)bis(3‐methyl‐1‐phenyl pentylidene)dilithium initiator concentration on the modality of polybutadiene

“…Organo dilithium compounds are of great interest as difunctional initiators, especially in the anionic polymerization of dienes, because of their potential for simple two‐step syntheses of A‐B‐A triblock copolymers [e.g., where A: polystyrene and B: polyisoprene or polybutadiene (PBd)] with low vinyl content for the central dienic block 5, 6. Furthermore, they allow for the preparation of cyclic polymers via reaction of a telechelic (α,ω‐difunctional) living polymer with the appropriate difunctional linking agent in dilute solution 7…”

One-Pot Synthesis of Natural Rubber-Based Telechelic cis-1,4-Polyisoprenes and Their Use To Prepare Block Copolymers by RAFT Polymerization

“…Telechelic unsaturated polymers are good candidates to obtain block copolymers with a wide range of applications. For instance, block copolymers containing polyisoprene (PIp) as a constituent have found applications as nanofibers, thermoplastic elastomers, pressure sensitive adhesives, , and biocompatible materials. , The PIp block is essentially synthesized by living anionic polymerization of isoprene (Ip), − by controlled/living radical polymerization (CRP) of isoprene, − or ring-opening metathesis polymerization of 1,5-dimethyl-1,5-cyclooctadiene . The cis -1,4-polyisoprene block can be obtained from natural rubber (NR) which is a biomacromolecule and a renewable resource.…”