Synthesis of poly(ε-caprolactone)-block-poly(n-butyl acrylate) by combining ring-opening polymerization and atom transfer radical polymerization with Ti[OCH2CCl3]4 as difunctional initiator: I. Kinetic study of Ti[OCH2CCl3]4 initiated ring-opening polymerization of ε-caprolactone

A new titanium alkoxide, Ti[OCH2CCl3]4, designed to combine the ring-opening polymerization (ROP) of 3-caprolactone and atom transfer radical polymerization (ATRP) of n-butyl acrylate, was synthesized through the ester-exchange reaction of titanium n-propoxide and 2,2,2-trichloroethanol. The mechanism and kinetics of Ti[OCH2CCl3]4 initiated bulk polymerization of 3-caprolactone were studied. The results demonstrate that the polymerization proceeds through the coordination-insertion mechanism and all the four alkoxide groups in Ti[OCH2CCl3]4 share a similar activity in the initiation. The determined polymerization activation energy is 70 kJ/mol. The polymerization process can be well predicted by the obtained kinetic parameters. Furthermore, PCL synthesized with Ti[OCH2CCl3]4 can be used as the macroinitiator in ATRP of n-butyl acrylate to synthesize poly(3-caprolactone)-block-poly(n-butyl acrylate) (PCL-b-PBA) copolymer.