Polylactones—18. Polymerization of l,l-lactide with Sn(II) and Sn(IV) halogenides
Polylactones—18. Polymerization of l,l-lactide with Sn(II) and Sn(IV) halogenides
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聚内酯—18. L,L-丙交酯与卤化锡 (II) 和卤化锡 (IV) 的聚合
DOI：
10.1016/0014-3057(89)90010-4
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Movita‐Verena Sumbél
中科院分区：
文献类型：
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作者：
H. Kricheldorf;Movita‐Verena Sumbél
以SnCl 2、SnBr 2、SnCl 4和SnBr 4为引发剂，在不同温度下进行了1，1-丙交酯的本体聚合。尽管反应时间长（48小时），但在100-160°范围内没有发现外消旋化。在180°下，反应时间需要缩短到几个小时以避免外消旋化。在如此高的温度下不存在外消旋化是非离子插入机制的明确指示。最高的数均分子量（Mn = 50，000）与SnBr 4和SnCl 2。分子量基本上是独立的单体/引发剂的比例，但他们增加的1，1-丙交酯的纯度。通过深度纯化，可以获得M ↓ [n] s高达10 5的反应物。通过1H-NMR光谱检测到乳酸或其线性二聚体作为1，1-丙交酯的污染物，显然起共引发剂的作用。它也表明，微量的HBr或HCl不引发1，1-丙交酯的阳离子聚合。
Bulk polymerizations of l, l-lactide initiated with SnCl 2, SnBr 2, SnCl 4 or SnBr 4 were conducted at various temperatures. No racemization was found in the range 100–160° despite long reaction times (48 hr). At 180° the reaction time needs to be shortened to a few hours to avoid racemization. The absence of racemization at such high temperatures is a clear indication of a non-ionic insertion mechanism. The highest number-average molecular weights (M ̄ n= 50,000) were obtained with SnBr 4 and SnCl 2. The molecular weights were essentially independent of the monomer/initiator ratio, yet they increased with the purity of l, l-lactide. With intensively purified, reactants M ̄ n s up to 10 5 may be obtained. Lactic acid or its linear dimer, which were detected by 1 H-NMR spectroscopy as contaminants of l, l-lactide, obviously play the role of co-initiators. It is also demonstrated that traces of HBr or HCl do not initiate cationic polymerization of l, l-lactide.