This article describes a new concept of copolymerization which occurs spontaneously without any added catalyst. A nucleophilic monomer (MN) combines with an electrophilic one (ME) to generate a zwitterion [+]MN—M, which is responsible for the initiation and propagation of copolymerization. Twenty-three novel copolymerizations have been explored on the basis of the new concept. MN monomers which have been investigated are five- and six-membered cyclic imino ethers, dihydro-2(3H)-furanimine, an azetidine, a cyclic phosphinic acid ester and a Schiff base; the ME monomers include β-propiolactone, a cyclic dicarboxylic acid anhydride, a sultone, acrylic acid, acrylamide, a β-hydroxyalkyl acrylate and ethylenesulfonamide. In most combinations, alternating 1 : 1 copolymers were produced. In addition to the above-mentioned combinations, the alternating 1 : 1 copolymerization of cyclic phosphite with α-keto acid was discovered.