合成,结构,机械和计算研究单位β-diketiminate锡 (II) 启动剂用于rac-lactide的聚合
Andrew P Dove1, Vernon C Gibson, Edward L Marshall
1Department of Chemistry, Imperial College London, UK.
Journal of the American Chemical Society
|July 27, 2006
概括
锡 (II) β-二甲基二胺酸复合物启动rac-lactide的受控聚合,产生异质性多聚化. 带结构和锡的结构.
科学领域:
- 协调化学 协调化学
- 聚合物科学 聚合物科学
- 有机金属化学 有机金属化学
背景情况:
- () 复合物被探索为乳酸盐聚合物的启动剂.
- β-二甲基胺酸提供可调节的固体和电子特性.
- 乳化物的受控聚合对于生物降解的聚合物合成至关重要.
研究的目的:
- 研究 (II) β-二甲基二胺酸复合物作为rac-lactide聚合的启动剂.
- 阐明影响聚合动力学和立体选择性的结构-活性关系.
- 了解乳化物插入的机制和诱导周期的起源.
主要方法:
- 的合成和表征 (II) β-二甲胺酸复合物.
- 使用各种 (II) 启动剂对rac-lactide聚合物的动力学研究.
- 聚合物分子重量,分布和战术性的分析.
- 进行X射线晶体学和密度函数理论 (DFT) 计算.
主要成果:
- 实现了对rac-lactide的良好控制的"活体"聚合,以线性M(n) 和[M](o) /[I](o) 与转换图表以及狭窄的分子量分布 (Đ = 1.07-1.10) 表示.
- 聚合速率受到连接体硬质阻碍和锡 (II) 中心的易斯酸度的影响,易斯酸复合体较少受到阻碍,更多的易斯酸复合体表现出增强的活动.
- 所有的发起者都表现出对异质性多聚胺的偏见,这归因于由Sn ((II) 孤独对主导的链末控制机制.
- 一个模型 (II) 异 (S) 乳酸盐复合物被合成和特征化;DFT研究显示易于初始乳化物插入,但随后的插入速度较慢,解释了观察到的诱导期.
结论:
- (II) β-二甲基二胺酸复合物是受控的rac-lactide聚合物的有效启动剂.
- 立体选择性主要由 (II) 中心的电子特性,特别是单一对,而不是连接体效应来决定.
- 在聚合过程中,诱导周期与单体插入成长中的聚合物链的动力学有关.
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