Dependence of color change of vinylethylene carbonate copolymers having N-substituted maleimides on chemical structure by acid-base switching in solution and solid state

Abstract

The copolymers of vinylethylene carbonate (VEC) and N-substituted maleimide (NMI) having various N-substituents were synthesized by radical polymerization. The color of P(VEC/NMI)s changed from colorless to red reversibly based on the acid-base switching in solution and solid state. Furthermore, the color depth of P(VEC/NMI) solution and powder changed systematically depending on the electric effect of N-substituents. However, the copolymers of styrene and NMIs barely changed under the same conditions. These color change and depth behaviors of NMI copolymers were analyzed in detail by UV–vis and IR spectra, and the results were also supported by the density functional theory (DFT) calculation for the model compound of maleimide tautomers. Additionally, the powder color of P(VEC/NMI)s changed reversibly before and after exposure to cigarette smoke and vinegar.