Development of a new end-functionalization technique in polymer synthesis
Vinyl polymerization (polymerization of vinyl compounds) is a useful method for preparing sp3-carbon-based main-chain polymers including commodity plastics, where the polymer backbone is constructed from a two-carbon unit derived from vinyl groups of monomers.
In contrast, polymerization of diazo compounds can construct the polymer backbone from one carbon unit, also giving sp3-carbon based main-chain polymers. For the latter C1 polymerization system, the diazoacetate is a suitable monomer, producing polymers with an alkoxycarbonyl group (ester) on each main-chain carbon atom [poly(alkoxycarbonylmethylene)s].
Scientist have successfully developed a new initiating system for the polymerization of diazoacetates. More specifically, they have demonstrated that the newly prepared Pd(0) complexes bearing N-arylmaleimide as a ligand, in conjunction with a borate such as NaBPh4, are effective in producing a good yield of polymers by the polymerization of diazoacetates; in particular, the polymerization proceeds in a highly uniform manner with respect to initiation, propagation, and termination.
The most remarkable feature they found about the initiating system [Pd(N-arylmaleimide)/NaBPh4] is that an N-arylmaleimide molecule, which was originally coordinated on the Pd center, was incorporated into the α-chain end of the resulting polymer almost quantitatively.
Accordingly, the initiating system will enable one to introduce a variety of functional groups at the α-chain end of poly(alkoxycarbonylmethylene)s by using N-substituted maleimide bearing a (protected) functional group. The findings—described in Macromolecules—will contribute to broadening the generality and utility of diazoacetate polymerization, which has been gaining importance as a useful method for preparing sp3-carbon-based main-chain polymers.
New palladium-based initiating systems for C1 polymerization of diazoacetates
Hiroaki Shimomoto et al, Polymerization of Diazoacetates Initiated by the Pd(N-arylmaleimide)/NaBPh4 System: Maleimide Insertion into a Pd–C Bond Preceding to Initiation Leading to Efficient α-Chain-End Functionalization of Poly(alkoxycarbonylmethylene)s, Macromolecules (2022). DOI: 10.1021/acs.macromol.2c00508
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Development of a new end-functionalization technique in polymer synthesis (2022, September 2)
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