The ring-opening polymerization (ROP) of the cyclic phosphoester 2-ethoxy-2-oxo-1,3,2-dioxaphospholane (EEP) in tetrahydrofuran solution with co-initiation of stannous octoate and dodecanol yields poly(ethylene ethlyl phosphate) (PEEP) with defined linear molecular structure. NMR analyses reveal every molecule of dodecanol starts growth of one PEEP chain and each polymer chain bears one hydroxyl end group. Kinetics studies for different co-initiator ratios and temperatures reveal that the ROP is a first-order reaction with respect to EEP monomer and suggest the formation of active center stannous alkoxide and a coordination−insertion polymerization mechanism. Side chain transfer leading to branched polymeric structure was observed particularly when the reaction time was extended after monomer consumption reaching equilibrium due to the pentavalent nature of phosphorus. By controlling the polymerization conditions, such side reaction can be suppressed to synthesize polyphosphoester with confined structure. This polymerization procedure is expected to facilitate the synthesis of polyphosphoesters with defined molecular architectures and properties for further biomedical applications.

中文翻译：

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辛酸亚锡引发的2-乙氧基-2-氧代-1,3,2-二氧杂戊环聚合反应的动力学和机理

环磷酸酯2-乙氧基-2-氧代-1,3,2-二氧戊环烷（EEP）在四氢呋喃溶液中与辛酸亚锡和十二烷醇的共引发的开环聚合（ROP）产生聚（乙烯乙基磷酸乙二酯）（ PEEP）具有定义的线性分子结构。NMR分析显示十二烷醇的每个分子都开始一个PEEP链的生长，每个聚合物链带有一个羟基端基。对于不同的共引发剂比率和温度的动力学研究表明，相对于EEP单体，ROP是一阶反应，并提示了活性中心亚锡醇盐的形成和配位插入聚合机理。由于磷的五价性质，​​特别是当单体消耗达到平衡后延长反应时间时，观察到侧链转移导致分支的聚合物结构。通过控制聚合条件，可以抑制这种副反应以合成具有受限结构的聚磷酸酯。预期该聚合程序将促进具有确定的分子结构和性质的聚磷酸酯的合成，以用于进一步的生物医学应用。