Isomerization Polymerization of Lactams

Isomerization polymerization affords a macromolecule whose repeating unit is derived from an isomer of the original monomer. Thus hexa- and heptacyclic β-carboxymethyllactams yield polymers containing glutarimide units, whereas penta- and hexacyclic β-carboxylactams furnish polymers containing succinimide units. Some dimethyl derivatives of β-carboxylactams isomerize or rearrange, and 5-oxopyrrolidine-3-acetic acid does not react at all. These observations can be explained in terms of a bicyclic intermediate.