Isospecific Group-Transfer Polymerization of Diethyl Vinylphosphonate and Multidimensional NMR Analysis of the Polymer Microstructure

Control of stereoregularity is an integral part of a precision polymerization method and for the development of functional materials. Yttrium- and aluminum-based catalysts are known for converting diethyl vinylphosphonate (DEVP) into its stimuli-responsive polymer in a precise but stereoirregular way. Herein, we present Y- and Al-based constrained geometry complexes (CGCs) to induce isotacticity without losing control over other macromolecular parameters. After having established convenient synthesis routes and detailed structural analyses, these CGCs showed exceedingly high turn-over frequencies (up to 45 000 h–1) in the group-transfer polymerization of DEVP. The initiator efficiencies (≤99%) and dispersities (≤1.02) strongly depended on the substitution pattern of the applied ligands. An analysis of the microstructure using multidimensional NMR (1H–1H and 1H–13C­(−31P)) correlation experiments demonstrated significant disparities for the stereospecificity of the CGCs and enabled a reliable signal assignment. The yttrium catalysts produced highly isotactic poly­(diethyl vinylphosphonate), likely following a chain-end control mechanism, whereas the aluminum complexes produced less defined polymers.立体规整性调控是精准聚合方法与功能材料开发的核心组成部分。已知钇基与铝基催化剂可将乙烯基膦酸二乙酯（diethyl vinylphosphonate, DEVP）转化为刺激响应型聚合物，但其聚合过程虽精准，所得聚合物的立体规整性却较差。本文报道了一类钇基与铝基受限几何配合物（constrained geometry complexes, CGCs），可在不影响其他大分子参数调控的前提下，诱导聚合物生成等规结构。在建立便捷的合成路线并完成详细的结构表征后，这类CGCs在DEVP的基团转移聚合中展现出极高的转化频率（最高可达45000 h⁻¹）。引发剂效率（≤99%）与聚合物分散度（≤1.02）均与所使用配体的取代模式密切相关。通过多维核磁共振（¹H–¹H及¹H–¹³C(-³¹P)）相关谱对聚合物微观结构进行分析，结果显示不同CGCs的立体定向性存在显著差异，同时实现了可靠的NMR信号归属。钇基催化剂可制备高等规度的聚(乙烯基膦酸二乙酯)，其聚合过程大概率遵循链端控制机理；而铝基配合物所得聚合物的结构规整度则相对较差。