Synthesis of branched polymers by means of living anionic polymerization. 12. Anionic synthesis of well-defined star-branched polymers by using chain-end-functionalized polystyrenes with dendritic benzyl bromide moieties

A series of five well-defined chain-end-functionalized polystyrenes with 2, 4, 8, 16, and 32 benzyl bromide moieties that were dendritically distributed were synthesized by an iterative methodology using only two sets of the reactions in each iterative reaction sequence. By coupling of these benzyl bromide-functionalized polystyrenes with 1,1-diphenylethylene (DPE)-end-capped polystyryllithium or polyisoprenyllithium in THF at -40 degreesC, 3-, 5-, 9-, 17-, and 33-arm star-branched polystyrenes as well as AA'(8) and AB(8) asymmetric star-branched polymers were quantitatively synthesized. Moreover, a new chain-end-functionalized polystyrene with 16 phenols could successfully be synthesized by a similar coupling reaction between chain-end-functionalized polystyrene with 8 benzyl bromide moieties and the functionalized 1,1-diphenylalkyl anion prepared from see-BuLi and 1,1-bis(4-tert-butyldimethylsilyloxyphenyl)ethylene, followed by deprotection. The well-defined structures and branched architectures of the resulting star-branched and chain-end-multifunctionalized polymers were confirmed by SEC, vapor pressure osmometry (VPO), H-1 NMR, SLS, and viscosity measurements.