Stereoselective Ring-Opening Polymerization of rac-Lactide Using Organocatalytic Cyclic Trimeric Phosphazene Base,ACS Macro Letters

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Stereoselective Ring-Opening Polymerization of rac-Lactide Using Organocatalytic Cyclic Trimeric Phosphazene Base
ACS Macro Letters ( IF 5.1 ) Pub Date : 2018-05-16 00:00:00 , DOI: 10.1021/acsmacrolett.8b00353
Shaofeng Liu ₁ , Huaike Li ₁ , Na Zhao ₁ , Zhibo Li ₁

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Phosphazene base is an important organocatalyst in polymer chemistry owing to its high activity and versatility. In this contribution, we demonstrate that cyclic trimeric phosphazene base (CTPB) can catalyze stereoselective ring-opening polymerization (ROP) of rac-lactide (rac-LA) to produce isotactic stereoblock PLA (P_i up to 0.93). The polymerizations are highly controlled, as evidenced by linear relationship between molecular weights (MW) and monomer conversions and the narrow dispersity (Đ = M_w/M_n) of the resulted polymers with high fidelity of end groups. The investigations on polymerization parameters show that the tacticity of produced PLA depends on the polymerization temperatures and solvents, while the kinetic studies reveal a faster rate for ROP of l-LA as compared to rac-LA under same conditions. Based on these results, the chain end control mechanism is proposed to explain the production of isotactic stereoblock PLA from rac-LA by an achiral catalyst.

中文翻译：

有机催化环状三聚体磷腈基外消旋丙交酯的立体选择性开环聚合

磷腈碱因其高活性和多功能性而成为高分子化学中重要的有机催化剂。在这项贡献中，我们证明了环状三聚体磷腈碱 ( CTPB ) 可以催化外消旋丙交酯 ( rac -LA)的立体选择性开环聚合 (ROP)以产生等规立构嵌段 PLA ( P _i高达 0.93)。聚合受到高度控制，如分子量 (MW) 和单体转化率之间的线性关系和窄分散性 ( Đ = M _w / M _n) 得到的具有高保真端基的聚合物。对聚合参数的研究表明，生成的 PLA 的立构规整度取决于聚合温度和溶剂，而动力学研究表明，在相同条件下，与rac -LA相比， l -LA 的 ROP 速率更快。基于这些结果，提出了链端控制机制来解释通过非手性催化剂从rac -LA 生产等规立构嵌段 PLA。

更新日期：2018-05-16

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