Ring‐opening‐closing alternating copolymerization via zwitterion intermediates

The present paper describes comprehensive results based on a new concept, i.e., ring‐opening‐closing alternating copolymerization. The copolymerization is given by combinations of ring‐opening of a cyclic monomer (A) and ring‐closing of a non‐cyclic monomer (B). The cyclic monomers used are five‐, six‐, and seven‐membered cyclic phosphonites and 2‐methyl‐2‐oxazoline. As a monomer (B), muconic acid, dialdehydes, di(meth)acrylic anhydrides, and N ‐methyldiacrylamide are used. A 1:1 mixture of these monomers produced an alternating copolymer having a ring‐opened and a ring‐closed structural unit. A mechanism involving zwitterion intermediates is considered in all copolymerizations.