The controlled/living cationic polymerization of α-methylstyrene (αMeSt) and sequential block copolymerization of isobutylene (IB) with αMeSt were achieved using 2-chloro-2,4,4-trimethylpentane (TMPCl)/titanium tetrachloride (TiCl4)/titanium isopropoxide (Ti(OiPr)4)/2,6-ditert-butylpyridine (DtBP) initiating system in CH3Cl/hexane (50/50 v/v) solvent mixture at -80 ℃.The polymerization rate decreased with increasing [Ti(OiPr)4]/[TiCl4] ratio in the homopolymerization of αMeSt. The effects of [Ti(OiPr)4]/[TiCl4] ratios and PIB+ molecular weight on the polymerization rate and blocking efficiency were also investigated. Well-defined poly(isobutylene-b-α-methylstyrene)s were demonstrated by 1H-NMR and triple detection SEC; refractive index (RI), multiangle laser light scattering (MALLS) and ultraviolet (UV) detectors. Blocking efficiencies for the poly(isobutylene-b-α-methylstyrene)s of almost 100% were obtained when αMeSt was induced by PIB's of Mn ≥ 41000 at [Ti(OiPr)4]/[TiCl4]=1. Differential scanning calorimetry (DSC) of the block copolymers showed two glass transition temperatures, thereby demonstrating microphase separation.

Keywords: controlled/living carbocationic polymerization; poly(α-methylstyrene); kinetics; poly(isobutylene-b-α-methylstyrene)