Synthesis of End-Reactive Monodisperse Polyamides by Living Anionic Polymerization of beta-Lactams

在含5wt%氯化锂的N，N-二甲基乙酰胺溶液中，于25ﾟ℃下实现了3，3-二甲基内酰胺和4，4-二甲基-2氮杂二酮两种甲基取代β-内酰胺的活性阴离子聚合，并定量地进行了均相聚合。凝胶渗透层析法发现，所得聚酰胺的相对分子质量分布较窄。由1H-核磁共振谱峰强度估算的数均分子量与消耗的内酰胺与相应的用作活化剂的N-苯甲酰基衍生物的摩尔比计算的结果几乎相同。此外，还对酰内酰胺类生长链端进行了定量修饰，聚合后通过与苯甲胺的反应实现了内酰胺类的活性阴离子聚合。为了实现内酰胺类的活性阴离子聚合，应在温和的条件下聚合除氮原子以外没有活性氢的高活性内酰胺。在目前的调查中，我们尝试了…3，3-二甲基-3，4-二甲基-3，4-二甲基和3-甲基-2-氮杂环丁酮(分别为1，2和3)与三种β-内酰胺类化合物进行更活泼的阴离子聚合，得到单分散的聚酰胺。在N，N-二甲基乙酰胺(DMAc)和氯化锂(LiCl2)的混合液中，分别用相应的N-苯甲酰内酰胺和吡咯烷酸钾作为活化剂和催化剂，在25ﾟC下进行均相聚合。用含LiCl的DMAc作淋洗液进行凝胶渗透色谱(GPC)测定，发现1和2得到的聚酰胺具有窄的分子量分布(MW/Mn&lt1.1)。另一方面，由3制备的聚酰胺的M_W/M_n值为1.2-1.3，但在聚合过程中没有观察到终止现象。从相应的酰基内酰胺的氨解动力学分析结果推测，加宽主要是由于阴离子聚合中引发反应常数与引发反应常数之比较低所致。

Living anionic polymerization of two kinds of methyl-substituted beta-lactams, 3, 3-dimethyl-, and 4, 4-dimethyl-2azetidinones, was attained at 25ﾟC in N, N-dimethylacetamide containing 5 wt% of lithium chloride and proceeded in a homogeneous phase quantitatively. The resulting polyamides were found to have a narrow molecular weight distribution from the gel permeation chromatography. The number average molecular weights estimated from the peak intensities in the ^1H-NMR spectra were almost equal to those calculated from the mole ratio of the consumed lactam to the corresponding N-benzoyl derivative used as an activator. In addition, the acyllactam-type growing chain ends were modified quantitatively by the reaction with benzylamine after the polymerization.In order to attain the living anionic polymerization of lactams, highly reactive lactams having no active hydrogen except on the nitrogen atoms should be polymerized under mild conditions. In the present investigation, we tried the … More living anionic polymerization of three beta-lactams, 3, 3-dimethyl-, 4, 4-dimethyl-, and 3-methyl-2-azetidinones (1, 2, and 3, respectively) to give monodisperse polyamides. Their polymerization using the corresponding N-benzoyl lactams and potassium pyrrolidonate as activators and a catalyst, respectively, in the mixture of N, N-dimethylacetamide (DMAc) with lithiium chloride (LiCl) proceeded in a homogeneous phase at 25ﾟC.The polyamides obtained from 1 and 2 were found to have a narrow molecular weight distribution (M_W/M_n<1.1) from GPC measurement using DMAc containing LiCl as an eluent. On the other hand, the value of M_W/M_n for the polyamide prepared from 3 was 1.2-1.3, although no termination was observed during the polymerization. From the results of the kinetic analysis of the aminolysis of the corresponding acyllactams, the broadening was speculated to be caused mainly by a low value of the ratio of the initiation reaction constant to the propagation one in the anionic polymerization of 3. Less