New Activating Agents for the Anionic Polymerization of Lactams

Abstract

Metal dialkylaluminum hydrides and strong bases (NaH, BuLi) associated with reducing agents [(alkyl)2AlH, (alkyl)2BH, RMgBr] are shown to form a new class of activating agents for the anionic polymerization of lactams. Upon treating e-caprolactam (ϵCL) with these new activating agents, active species of reduced nucleophilicity, as compared to the mere caprolactamate anions, are obtained. Once deprotonated, the monomer undergoes a reduction by these activating agents at its carbonyl position. These active species behave very similarly to sodium 2-(diaIkoxyaluminoxy)-1-azacycloheptane, a salt obtained upon reacting eCL with sodium dialkoxyaluminum hydride (NaAlH2(OR)2) and whose contribution to the polymerization of lactams has been thoroughly investigated.1 From these similarities, it is suggested that the mechanism of polymerization which occurs in the presence of these new activating agents should be very much the same as that discovered for NaAlH2(OR)2. © 1992, American Chemical Society. All rights reserved.