Synthesis of monodisperse polyamides by living anionic polymerization of β‐lactams in the mixture of N,N‐dimethylacetamide and lithium chloride

Abstract

SYNOPSISLiving anionic polymerization of two kinds of methyl-substituted /3-lactams, 3,3-dimethyl-, and 4,4-dimethyl-2-azetidinones, was attained at 25°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 'H-NMR spectra were almost equal to those calculated from the mol ratio of the consumed lactam to the corresponding N-benzoyl derivative used as a n activator. In addition, the acyllactam-type growing chain ends were modified quantitatively by the reaction with benzylamine after the polymerization. 0

Synthesis and characterization of poly(4-alkyl-4-methyl-2-azetidinone)s

“…Their chemical resistance and melting temperature depend on the chain stereoregularity and the nature of the substituents. More recently, using a variety of initiators, the living polymerization of 3-butyl-3-methyl-2-azetidinone, 6 of a series of 3-alkyl-3-methyl-2-azetidinones, [7][8][9] and of 4,4-dimethyland 3,3-dimethyl-2-azetidinone 10 was reported, confirming the general behavior mentioned above. Finally, Carrière et al 11 studied the polymerization of optically active 3-ethyl-3-phenyl-2-azetidinone and observed, first, that there is a direct correlation between the optical purity of the monomer and the melting temperature of the resulting polymer (193-310°C) and, second, that the atactic polymer exhibits no melting point but only degradation.…”

“…1 Thus, the number of resulting polyamide molecules is equal to that of the activator, and its molecular weight can be estimated from the molar ratio of the consumed monomer to the activator, if no side reaction occurs during the polymerization. 10 The difference here observed between the experimental and expected molecular weights (Table III) indicates that the polymerization does not occur via a living mechanism, and that side reactions are present, contrary to the living polymerization of the same monomer in a N,N-dimethylacetamide/lithium chloride mixture. 10 This difference can be explained by the nature of the solvent that leads, in this latter case, to the complete solubilization of the monomer and polymer until the end of the polymerization.…”

“…These compounds, as, for instance, acylating compounds, which form N-acyl-␤-lactams in the initiation reaction, allow the polymerization of ␤-lactams in solution under mild conditions. 1,10 The lithium salt of the monomer derivative used here as activator was soluble in DMSO and the resulting solution was yellow. The conditions of polymerization and the resulting yields are given in Table III.…”

Proton transfer-controlled anionic polymerization of methyl-substituted ?-lactams with potassiumt-butoxide and subsequent coupling reaction with saccharides

“…10 The N-benzoyl derivatives of 1 and 2 were also prepared by the same methods as described in previous articles. 18,20 Commercially available potassium t-butoxide was used without purification.…”

“…5 We previously demonstrated the potassium pyrrolidonate-catalyzed living anionic polymerization of 3,3-dimethyl-and 4,4-dimethyl-2-azetidinone (structures 1 and 2, respectively) in a mixture of N,N-dimethylacetamide and lithium chloride at 25°C to yield the corresponding monodisperse polyamides. 10,11 The selection of the polymerization solvent was one of the key conditions for the living polymerization of ␤-lactams 1 and 2. In this system the initiation step is demonstrated to involve the nucleophilic attack of the lactamate anion on the endocyclic carbonyl group in the acyllactam called the activator 12 and the subsequent proton transfer from another lactam molecule to the resulting amidate anion, according to "the activated monomer mechanism."…”