Abstract:

Polyisobutylenes (PIBs) have excellent properties in chemical stability, thermal stability and resistance to oxidation, ozone and UV. The controlled/living cationic polymerizations of isobutylene (IB) near 100% of initiation efficiency have been achieved. PIBs or living PIB chains with designed number-average molecular weights (Mn) and narrow molecular weight distributions could be obtained. Livingness of cationic polymerization of IB was further confirmed by all monomer in (AMI) technique and incremental monomer addition (IMA) technique.
Stereoregularity is one of the most important factors to affect seriously the crystallinity and physical properties of polymers. It is really rather difficult to achieve high stereoregulation in cationic polymerization for the lack of controlling the stereochemistry and only few stereoregular polymers could be prepared. The stereospecific cationic polymerization of methylstyrene could be achieved in the presence of bulky triphenylamine and the polymers with several isotactic and atactic segments along macromolecular chains could be obtained. The crystallizable polymethylstyrene with high average-number molecular weights and high meso dyad (m) content of 81% could be prepared. The polymethylstyrene samples with predominant isotacticity could form crystal morphology with 10 ~ 20 μm in size by flow-induced crystallization under pressure at 180 ℃.
The triblock copolymers of PS-b-PIB-b-PS and PMS-b-PIB-b-PMS with totally saturated soft segments and crystallizable hard segments could be successfully synthesized via the combination of living cationic polymerization with stereospecific cationic polymerization by sequential monomer addition. The mechanical property and thermal property of these triblock copolymers have been improved. The self-assembly behavior and micromorphology of these polyisobutylene-based copolymers have been also investigated.
Keywords: Polyisobutylene；Thermoplastic Elastomer; stereoregulation

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