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

在含有5 wt%氯化锂的N， N-二甲基乙酰胺中，在25℃的温度下，获得了3,3 -二甲基-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，并在均相中进行了定量。凝胶渗透层析发现所得聚酰胺具有窄分子量分布。由^1H-NMR谱峰强度估计的数平均分子量几乎等于由消耗的内酰胺与用作活化剂的相应n -苯甲酰衍生物的摩尔比计算的数平均分子量。此外，聚合后通过与苄胺的反应对酰基内酰胺型生长链末端进行了定量修饰。为了实现内酰胺的活性阴离子聚合，需要在温和的条件下聚合除氮原子外没有活性氢的高活性内酰胺。在本研究中，我们尝试了三种β -内酰胺，3,3 -二甲基-，4,4 -二甲基-和3-甲基-2-叠氮二酮（分别为1,2和3）的活性阴离子聚合，以得到单分散聚酰胺。在N， N-二甲基乙酰胺（DMAc）和氯化锂（LiCl）的混合物中，以相应的N-苯甲酰内酰胺和吡啶醛酸钾为活化剂和催化剂，在25℃的均相条件下进行聚合。用含LiCl的DMAc作为洗脱液进行GPC测量，发现1和2得到的聚酰胺分子量分布较窄（M_W/M_n<1.1）。另一方面，由3制备的聚酰胺的M_W/M_n值为1.2-1.3，尽管在聚合过程中没有观察到终止。从相应的酰基内酰胺的氨解动力学分析结果推测，增宽主要是由于3的阴离子聚合中引发反应常数与增殖反应常数之比较低所致。少

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