The preparation of a monodisperse hydrophilic polyamide was achieved in the anionic polymerization of a bicyclic oxalactam, 8‐oxa‐6‐azabicyclo[3.2.1]octan‐7‐one (abbreviated BOL) with the use of N‐benzoyl BOL and potassium pyrrolidonate (2 and 0.5 mol % to BOL, respectively) in dimethyl sulfoxide at 25°C. The number‐average molecular weight of the polyamide increased in direct proportion to the monomer conversion, and was consistent with the value calculated from the amounts of the consumed monomer and activator. The molecular weight distribution (MWD) of the polyamide obtained until the middle stage of polymerization (polymerization time, < 10 min; monomer conversion, < 60%) was found to be narrow (Mw/Mn = 1.1). The MWD was gradually broadened in the later stage of the polymerization, which may result from the redistribution of molecular weight of the resulting polyamide not only by the polymerization–depolymerization equilibrium, but also by transamidation between polymer chains.

ABSTRACT:The aminolysis of N-acyllactams with n-butylamine was carried out in N,Ndimethylformamide at 25°C. The amine reacted with both of exo-and endocyclic carbonyl groups in the N-benzoyl derivatives of bicyclic oxalactams, such as 8-oxa-6-azabicyclo[3.2. l]octan-7-one (1) and the 4(e)-bromo-substituted analogue. In contrast, only the exocyclic carbonyl group in the monocyclic N-benzoyllactams, N-benzoyl-2-pyrrolidone and N-benzoyl-s-caprolactam, reacted under the same conditions. These results reflect high reactivity of the bicyclic oxalactams in the base-catalyzed ring-opening polymerization. The present aminolysis was kinetically analyzed in order to estimate the reactivity of N-acyllactams more quantitatively.

In the polymerization of various cyclic monomers, the equilibria were observed between the resulting polymers and the unreiicted monomers.'-3 Thus the equilibrium monomer concentrations or the thermodynamic parameters were estimated in the polymerization of several monocyclic lactams:-"The polymerizability of a variety of atom-bridged bicyclic lactams was also found by H. K. Hall, Jr.12 to be dependent upon their ring strain. This article will describe the equilibrium anionic polymerization of a bicyclic oxalactam, 8-oxa-6-azabicyclo[3.2.l]octan-7-one (1) and discuss its thermodynamic polymerizability.(1)Recently the anionic polymerization of 1 in dimethyl sulfoxide (Me,SO) at 25°C was found to give the monodipserse hydrophilic polyamide having an acyllactam-type growable end group (2).'3914 The number-average molecular weight of the polyamide increased in direct proportion to the monomer conversion and was consistent with the value calculated from the amounts of the consumed monomer and a~tivator.'~ From these results 1 can be speculated to have been polymerized without side reaction under the above-mentioned conditions. Nevertheless, the monomer conversion has not yet reached 100% under any Polymerization ~ondition.'~-'~ The refore, we expect the existence of the monomer-polymer equilibrium in the polymerization of 1.In the present work, the polymerization of 1 activated with N-(p-nitrobenzoy1)-8-oxa-6-azabicyclo[3.2.l]octan-7-one in Me,SO at 25°C was first followed by the gravimetrical determination of the resulting polyamide, and the residual monomer concentration ( [ M I , ) was found to reach 0.36 mol/L in about 20 min.'4 The polymer-