Kinetic studies on homopolymerization of α-methylstyrene and sequential block copolymerization of isobutylene with α-methylstyrene by living/controlled cationic polymerization

The controlled/living cationic polymerization of alpha-methylstyrene (alpha MeSt) and sequential block copolymerization of isobutylene (IB) with alpha MeSt were achieved using 2-chloro-2,4,4-trimethyl-pentane (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 degrees C. The polymerization rate decreased with increasing [Ti(OiPr)(4)]/[TiCl4] ratio in the homopolymerization of alpha MeSt. 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-alpha-methylstyrene)s were demonstrated by H-1-NMR and triple detection SEC; refractive index (RI), multiangle laser light scattering (MALLS) and ultraviolet (UV) detectors. Blocking efficiencies for the poly (isobutylene-b-alpha-methylstyrene)s of almost 100% were obtained when alpha MeSt was induced by PIB's of M-n >= 41000 at [Ti(OiPr)(4)]/[TiCl4] = 1. Differential scanning calorimetry (DSC) of the block copolymers showed two glass transition temperatures, thereby demonstrating microphase separation.