Abstract
The first efficient synthesis of poly(α-methylstyrene-b-isobutylene-b-α-methylstyrene) (PαMeSt-PIB-PαMeSt) triblock copolymer thermoplastic elastomers (TPEs) has been accomplished by living cationic polymerization using sequential monomer additions. Living PIB was prepared by the 5-tert-butyl-1,3-bis(1-chloro-1-methylethyl)benzene (tBuDicumcl)/TiclJHex :Mecl 60 :40 v :v/-80°C polymerization system. The living ends were capped by 1,1-diphenylethylene (DPE). TiCl 4 was replaced by SnBr 4 , followed by the addition of αMeSt. Triblock copolymers with close to theoretical molecular weights and narrow molecular weight distributions (M w /M n ∼1.1) were obtained. Homopolymer and diblock contamination have been found to be negligible. The thermal stability of the triblock copolymer was characterized by thermogravimetric analysis. Microphase separation was evidenced by the two glass transitions (at -65 and +180°C) observed by differential scanning calorimetry and in dynamic mechanical analysis. Triblock morphology was examined by transmission electron microscopy. Compression-molded samples with 16-45 wt % PαMeSt exhibited 12-24.5 MPa tensile strength, apparently directly related to the PαMeSt content and independent of the PIB molecular weight.
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