有机分子催化环酯类开环可控聚合机制的理论研究

Organo-catalyzed polymerization of cyclic ester can produce biocompatible and biodegradable polyester as drug carrier without metallic residues and has recently gained numerous attentions. However, organocatalyst systems showing stereocontrol over polymerization of ester, especially functional monomer, remained rare. And related theoretical knowledge is relatively lacking. The involvement of weak hydrogen bond makes the reaction mechanism difficult to be clarified just through experimental methods, which hampered the development of control polymerization of cyclic ester by organocatalysts. This proposal will adopt the method of computational chemistry to discover the mechanism of cyclic ester polymerization catalyzed organocatalyst. The interaction between catalyst/initiator and monomer during the monomer activation will be elucidated. The thermodynamic and kinetic properties of functional ester (co)polymerization will be explored. The nature of organo-catalyzed living polymerization of cyclic esters will be illuminated at the molecular level. The steric and electronic effects of stereoselective polymerization will be clarified. Based on aforementioned studies, the beneficially theoretical information on the design of novel both living and stereocontrol (co)polymerization systems by organocatalysts will be provided.

有机分子催化环酯聚合因其可制备无金属残留、生物相容和生物可降解的聚环酯药物载体受到人们的广泛关注。然而能够实现环酯的立体可控聚合以及功能性环酯聚合的有机体系相对罕见，相关理论基础欠缺，仅通过实验手段难以探明弱氢键参与的反应机制，从而妨碍了新型有机催化环酯可控聚合领域的发展。本项目拟运用计算化学手段，通过揭示有机催化环酯聚合的机理，明确催化剂、引发剂等在单体活化中的作用，探明功能性环酯均聚和共聚的热力学与动力学特征；从分子层面上阐明有机催化剂实现环酯活性可控聚合的内在本质，澄清影响立体选择性聚合的空间和电子因素；在此基础上，为设计和开发有机催化环酯活性聚合和立体可控聚合的新体系提供理论信息。

有机催化合成聚酯因其在医药和食品等领域的应用受到广泛专注。本项目通过密度泛函理论(DFT)计算对一系列有机分子催化环酯等极性单体聚合机理进行研究。获得主要研究结果如下：（1）在二氮杂二环/苄基醇(DBU/BnOH)体系催化磷酸酯(iBP)开环聚合中发现DBU主要引发BnOH和传递质子；在二氮杂二环/硫脲/苄基醇(DBU/TU/BnOH)体系中发现DBU诱导开环，TU通过双重氢键活化了单体，TU能够更好地活化单体P-O键有利于开环；（2）双功能甜菜碱(TMG)催化三亚甲基碳酸酯(TMC)开环聚合中发现亲核进攻为速控步，其分子内的CH3COO－和N(CH3)4+通过氢键作用分别活化单体和引发剂，适当延长CH3COO－和N(CH3)4+之间的碳链长度能够提高甜菜碱衍生物催化活性；（3）硫脲(TU)和有机碱(MTBD)共催化δ-戊内酯(δ-VL)开环聚合机理发现非极性甲苯溶剂作用下δ-VL开环聚合遵循氢键机理，极性丙酮溶剂作用下δ-VL开环聚合遵循酰化机理，丙酮可与MTBD形成了氢键作用提高聚合速率。（4）PPNCl/TEB催化环氧化物(CHO)/环酐/CO2共聚机理研究发现PA插入过程在热力学和动力学上均优于CO2插入，计算结果与实验结果一致。