"Highly Stereoselective Ruthenium-Catalyzed Ring-Opening Metathesis Polymerization of 2,3-Difunctionalized Norbornadienes and Their 7-Oxa Analogues"
Lionel Delaude, Albert Demonceau, and Alfred F. Noels
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source: e-Polymers
year: 2003
number: P_012
doi: not available
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Abstract:The stereoselective ring-opening metathesis polymerization (ROMP) of 2,3-dicarboalkoxynorbornadienes and their 7-oxa analogues was carried out in the presence of [RuCl2(p-cymene)]2. Previous studies from our group had already shown that this stable and readily available dimer was an efficient catalyst precursor for the ring-opening metathesis polymerization of low strain cyclic olefins when activated by a suitable carbene precursor, such as trimethylsilyldiazomethane (TMSD). The polymerization of 2,3-dicarbomethoxynorbornadiene served as a test reaction and the effect of various experimental parameters, such as nature of the solvent, reaction time and temperature, amount and nature of the diazo compound, were investigated. Strikingly, the addition of tricyclohexylphosphine significantly reduced the yield and the selectivity of the polymerization. Under optimal conditions, conversion reached 86% and a 99+%-trans, highly tactic poly(2,3-dicarbomethoxynorbornadiene) was obtained (Mn = 46 000, Mw/Mn = 1.7). The procedure could be successfully extended to various other 2,3-dicarboalkoxynorbornadienes, benzonorbornadiene, and their 7-oxa analogues. With the diester monomers, an increase of the alkyl substituent size led to a decrease of the polymer trans content and tacticity. Due to the readily availability and marked resistance to oxygen and water of the ruthenium catalyst, these reactions were very easy to set up and to carry out.
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