Tin‐coupled star‐shaped block copolymer of styrene and butadiene (I) synthesis and characterization

A new kind of star‐shaped block copolymer: tin‐coupled polybutadiene‐ b ‐ploy(styrene‐butadiene) ((SB‐B) 4 Sn) was synthesized by two‐stage anionic polymerization technology. A novel multifunctional organo‐lithium was used as initiator, and two different types of copolymers were formed, namely, S ‐PB‐PSB and S ‐PB‐PSB‐PS, depending on the styrene content in loading solution (St%). In copolymerization, the homo‐polybutadiene block was formed in the first reaction stage, and the residual blocks were formed in the second stage with the presence of tetrahydrofuran (THF). S ‐PB‐PSB was synthesized when the St% was lower than 34.9%, otherwise S ‐PB‐PSB‐PS was generated. Nuclear magnetic resonance (NMR) results showed that the amount of vinyl based upon the butadiene content within poly(butadiene‐styrene) blocks decreased dramatically as the St% was increased. Dynamic mechanical thermal analyzer (DMTA) spectra showed broadened loss peak as the St% was increased. Transmission electron microscopy (TEM) was employed to characterize the copolymer morphology, and the results showed different phase‐separated morphologies as St% increased. Mechanical property testing results indicated that these two copolymers met the requirements of high performance tire tread. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008