Synthesis of poly(cyclohexyl vinyl ether-b-isobutylene-b-cyclohexyl vinyl ether) triblock copolymer by living cationic sequential copolymerization

摘要

The living cationic polymerization of cyclohexyl vinyl ether (CHVE) and sequential block copolymerization of isobutylene with CHVE were carried out by the so-called capping-tuning technique in hexanes/CH3Cl solvent mixtures at -80degreesC. It involves capping the initiator, 2-chloro-2,4,4-trimethylpentane (TMPCl), or the living polyisobutylene (PIB) chain end with 1,1-ditolylethylene in the presence of titanium(IV) (TiCl4), followed by fine-tuning of the Lewis acidity with the addition of titanium(IV) isopropoxide (Ti(OIp)(4)) to match the reactivity of CHVE. Well-defined PCHVE, PIB-b-PCHVE and PCHVE-b-PIB-b-PCHVE with predesigned molecular weights and narrow molecular weight distributions (M-w/M-n<1.1) were thus prepared with [Ti(OIp)(4)]/[TiCl4] ratios of 1.6-1.8. Differential scanning calorimetry of the triblock copolymers showed two T(g)s (-62degreesC for PIB and 61degreesC for PCHVE) suggesting a microphas-separated morphology of the triblock copolymers and the potential use of them as thermoplastic elastomers.