LIVING CARBOCATIONIC POLYMERIZATION .36. LIVING CARBOCATIONIC POLYMERIZATION OF PARA-HALOSTYRENES .3. SYNTHESES AND CHARACTERIZATION OF NOVEL THERMOPLASTIC ELASTOMERS OF ISOBUTYLENE AND PARA-CHLOROSTYRENE

Novel linear and three‐arm star radial thermoplastic elastomers (TPE) comprising rubbery polyisobutylene (PIB) center blocks connected to glassy poly(p‐chlorostyrene) (PpClSt) outer blocks have been synthesized by sequential monomer addition. For triblock polymer synthesis isobutylene (IB) was added continuously to a bifunctional initiating system (dicumylmethyl ether/TiCl4) dissolved in CH3Cl/methylcyclohexane solvent mixture at –80°C. After the living PIB sequence has reached the desired molecular weight p‐chlorostyrene (pClSt) was added to produce the PpClSt end blocks. The synthesis conditions for the TPEs were developed with the help of model experiments using the 2‐chloro‐2,4,4‐trimethylpentane (TMPCl)/TiCl4 initiating system and subsequent PIB‐PpClSt diblock syntheses. The triblock and radiol block polymers after solvent extraction exhibited excellent TPE characteristics. Copolymer compositions were determined by 1H‐NMR and UV spectroscopy and further characterization was carried out by GPC, DSC, DMTA, and selective solvent extraction techniques. The TPEs exhibit two Tg's characteristic of glassy PpClSt (129°C) and rubbery PIB (−70°C) segments. Cast TPE films were clear and gave tensile strengths of 1.2‐21 MPa with elongations of 460–1500%. Transmission electron microscopy (TEM) of a triblock polymer containing ca. 38 wt % PpClSt suggests cylindrical PpClSt domains of 40–70 nm length and 25–35 nm diam embedded in a PIB matrix. Copyright © 1990 John Wiley & Sons, Inc.