Isospecific polymerization of vinyl ethers with titanium catalysts containing modified tridentate anionic donor ligands

BACKGROUND: Stereo-regulated polymerization of vinyl ethers (VEs) assumes significance because of its elegance and the resultant unique polymer properties. Although several Lewis acid catalysts polymerize VEs with good control of molecular weight, achieving stereo-regularity is quite challenging. There are literature reports of a few catalyst systems capable of producing highly isotactic poly(vinyl ether) (PVE) only at lower temperatures with the polymer becoming atactic with an increase in reaction temperature. Hence innovating new catalyst systems which can produce highly stereo-regular PVEs with high molecular weight at ambient temperature is quite challenging. RESULTS: We used two different titanium pre-catalysts (1-TiCl(2) and 2-TiCl(2)) for the polymerization of VEs. These pre-catalysts in combination with methylaluminoxane (MAO)/borate polymerized VEs in higher conversions. Highly isotactic poly(n-butylvinyl ether) (PBVE; 75% dyad isotactic ratio) was obtained with 1-TiCl(2)/MAO at ambient temperature. CONCLUSION: We synthesized unimodal and highly isotactic PBVE with molecular weights of the order of 10(5) g mol(-1) using the non-metallocene-type single-site catalyst system 1-TiCl(2)/MAO even at ambient temperature. The symmetry around the metal centre in the pre-catalyst and the polymerization temperature played a major role in controlling the stereo-regularization of the olefin inserted. (C) 2009 Society of Chemical industry