Introducing Polar Monomers into Polyisobutylene by Living Cationic Polymerization: Structural and Kinetic Effects

We report on the direct copolymerization of polar styrene monomers with isobutylene (IB) using living cationic polymerization with TiCl 4 /TMPCl as initiators, for the first time opening the possibility to introduce polar moieties in a direct copolymerization approach into PIB polymers. The investigated polar styrene monomers contain pyridine ( 1a ), collidine ( 1b, 1c ), thymine ( 2c ), and/or triazole moieties ( 2a − 2c ). Copolymerization with styrene monomers 1a, 1b, and 2c proceeded under incorporation of the comonomer into the PIB polymer (as proven by MALDI and NMR spectroscopy), whereas monomer 1c was not incorporated and resulted in broad polydispersities of the resulting PIB polymers. Inline-IR kinetic measurements of the monomer consumption demonstrated strong effects of the monomer structure on the polymerization kinetics, with rates of polymerization ( k p ) increasing up to a factor of 15. The addition of nonpolymerizable additives containing triazole moieties revealed a strong dependency on the attached residue R (R = hexyl ( 3a ), phenyl ( 3b ), p -methoxyphenyl ( 3c ), p -methylphenyl ( 3d ), p -chlorophenyl ( 3e )), with a decreasing rate of polymerization ( k p ) in the order of 3e > 3b > 3c > 3e > 3a = k p (IB). Measurements of k p / k −1 displayed significant changes with respect to homopolymerization of IB under the same conditions, proving that ion equilibria are disturbed by addition of the polar species during the IB polymerization.