Development of Highly Active and Regioselective Catalysts for the Copolymerization of Epoxides with Cyclic Anhydrides: An Unanticipated Effect of Electronic Variation
Recent developments in polyester synthesis have established several systems based on zinc, chromium, cobalt, and aluminum catalysts for the ring-opening alternating copolymerization of epoxides with cyclic anhydrides. However, to date, regioselective proc
Diciccio, Angela M.,Longo, Julie M.,Rodríguez-Calero, Gabriel G.,Coates, Geoffrey W.
Bimetallic Chromium Catalysts with Chain Transfer Agents: A Route to Isotactic Poly(propylene oxide)s with Narrow Dispersities
Bimetallic chromium catalysts are investigated for the enantioselective polymerization of propylene oxide. The catalyst is composed of two salen chromium species linked by an alkyl chain, the length of which significantly impacts the rate of polymerization. While the use of a chloride initiator on the catalyst resulted in bimodal molecular weight distributions, switching to a trifluoroacetate initiating group and adding a diol chain transfer agent afforded polymers of controllable molecular weight with low, unimodal dispersities.
Morris, Lilliana S.,Childers, M. Ian,Coates, Geoffrey W.
The invention is a novel bis(phosphoranylidene) ammonium salt useful as an initiator/catalyst in the reaction of oxirane groups in an epoxy resin with aromatic carbonate and/or ester linkages in monomeric, oligomeric, or polymeric carbonates, esters, or estercarbonates.
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(2008/06/13)
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