Renewable chain transfer agents for metallocene polymerizations: The effects of chiral monoterpenes on the polyolefin molecular weight and isotacticity

摘要

Monoterpenes were used as renewable chain transfer agents and polymerization solvents for metallocene/methylaluminoxane (MAO) catalysis. The polymerization of 1-hexene, ethylene, and propylene in d-limonene, hydrogenated d-limonene and a-pinene is reported. As detected by H-1 NMR analysis of the alkene region, chain transfer to d-limonene yielded a higher percentage of trisubstituted alkenes. Size exclusion chromatography detected a decrease in molecular weight values resulting from chain transfer to d-limonene. The [mmmm] pentads for isotactic polypropylene were characterized by C-13 NMR and FTIR spectroscopy. Propylene polymerizations with the Et(Ind)(2)ZrCl2/MAO and Me2Si(Ind)(2)ZrCl2/AIAO catalyst systems in d-limonene gave [mmmm] pentad values as high as 0.97. For the Et(Ind)(2)ZrCl2/MAO catalyst system at 0 degrees C, the mol fraction of [mmmml pentads increased from 0.86 to 0.94 upon switching the solvent from toluene to d-limonene. (c) 2007 Wiley Periodicals, Inc.