Well-defined Synthesis of Polyester by Living Anionic Alternating Copolymerization of Ketene and Aldehyde

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Living anionic alternating copolymerization of ethylphenylketene with various aromatic aldehydes was achieved. Butyllithium and tetrahydrofuran were used as an initiator and a solvent, respectively. Addition of lithium chloride was essential to obtain the corresponding polyester having narrow polydispersity. Various aromatic aldehyde such as methoxy-substituted and allyloxy-substituted benzaldehydes can be used as monomers. Copolymerization of ethylphenylketene with siloxy-substituted benzaldehyde was also successful. The corresponding polimer was obtained quantitatively, and its molecular weight distribution was narrow. Desilylation of the side chain siloxy group resulted in successful formation of the corresponding polyester having phenol moiety in the side chain. In addition, stereo-selective copolymerization was also accomplished. The relative stereochemistry in the repeating unit in the main chain was found to be well-controlled by solvent and additive used for the polymerization. The polymer was reductively degradated into the repeating unit, which was further derivatized into the molecule, whose single crystal was analyzed by X-ray to determine the relative stereochemistry in the polymer main chain. Utilization of optically active additive resulted in formation of optically active polyester, which was analyzed by polarometer and HPLC equipped with optically active column.