| Research Abstract |
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
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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
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