Maleimide polymers. I. A polymeric color reaction

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Abstract
Certain copolymers of maleimide and N‐substituted maleimides yield brilliant colors when treated with sufficiently strong basic reagents under nonhydrolytic conditions. For color generation, the copolymer must be capable of HX elimination. The chromophores which account for color probably result from the ionization of acidic protons in structures involving one or more double bonds conjugated with imide carbonyl. The analogy to the color reactions of aconitylanil is pointed out. Spectra covering the range of 330–700 mμ are presented for a number of copolymer–amine color‐generating systems. The colors produced in base with radical‐initiated polymaleimide and imidazole‐initiated poly‐N‐alkylmaleimides as well as the absence of color with anionic polymaleimide and radical poly‐N‐alkylmaleimides are discussed in light of what is known about their polymerization kinetics and mechanisms. Corresponding maleic anhydride copolymer systems are mentioned.