Polymerization of vinyl chloride with half-titanocene/methylaluminoxane catalysts

Abstract

The polymerization of vinyl chloride (VC) with half-titanocene /methylaluminoxane (MAO) catalysts is investigated. The polymerization of VC with the Cp*Ti(OCH3)3/MAO catalyst (Cp* = η5-pentamethylcyclopentadienyl) afforded high-molecular-weight poly(vinyl chloride) (PVC) in good yields, although the polymerization proceeded at a slow rate. With the Cp*TiCl3/MAO catalyst, the polymer was also obtained, but the polymer yield was lower than that with the Cp*Ti(OCH3)3/MAO catalyst. The polymerization of VC with the Cp*Ti(OCH3)3/MAO catalyst was influenced by the MAO/Ti mole ratio and reaction temperature, and the optimum was observed at the MAO/Ti mole ratio of about 10. The optimum reaction temperature of VC with the Cp*Ti(OCH3)3/MAO catalyst was around 20 °C. The stereoregularity of PVC obtained with the Cp*Ti(OCH3)3/MAO catalyst was different from that obtained with azobisisobutyronitrile, but highly stereoregular PVC could not be synthesized. From the elemental analyses, the 1H and 13C NMR spectra of the polymers, and the analysis of the reduction product from PVC to polyethylene, the polymer obtained with Cp*Ti(OCH3)3/MAO catalyst consisted of only regular head-to-tail units without any anomalous structure, whereas the Cp*TiCl3/MAO catalyst gave the PVC-bearing anomalous units. The polymerization of VC with the Cp*Ti(OCH3)3/MAO catalyst did not inhibit even in the presence of radical inhibitors such as 2,2,6,6,-tetrametylpiperidine-1-oxyl, indicating that the polymerization of VC did not proceed via a radical mechanism. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 248–256, 2003