Grafting of polycaprolactam on a polymethacrylate‐type backbone

Abstract Recently it has been found in our laboratories that ϵ‐caprolactam can be very readily polymerized by alkaline catalysts even at room temperature provided diacylamines, such as N ‐acetylcaprolactam, are present. As part of the investigation of the mechanism of this reaction, we have prepared polymers of N ‐methacryloylcaprolactam containing the active secondary imide groupings attached to a polymethacrylate‐type chain. Methacryloylcaprolactam itself will not, for obvious steric reasons, undergo polymerization, but its copolymers may readily, be obtained; thus it will form a copolymer with styrene with the parameters r 1 = 1, r 2 = 0. When this copolymer is allowed to react with caprolactam in the presence of alkaline catalysts, the monomer will enter at the sites of imide groupings. Simultaneously with the addition of the lactam to the copolymer, crosslinking of the polymer takes place which causes the formation of insoluble gels at the very beginning of the grafting. It is assumed that crosslinking is due to a reaction of the Claisen condensation type between two diacyl imide groups. This is supported by the fact that the relationship of the reciprocal specific viscosity and time is approximately linear in solution polymerization. The grafting of lactam which is not controlled by diffusion continues at an undiminished rate even after the gel formation. The rates of grafting and crosslinking are proportional to the concentration of sodium caprolactam added.