Donor/acceptor vinyl monomers and their polymers: Synthesis, photochemical and photophysical behavior

This review describes two classes of vinyl monomers bearing chromophores and their polymers based on the electron-accepting (A) or electron-donating (D) properties of vinyl double bonds, i.e., electron-poor vinyl monomers bearing electron-donating chromophores ([A(=)]n-D), and electron-rich vinyl monomers bearing electron-accepting chromophores ([D(=)]n-A). These D/A monomers generally display no or weak fluorescence, while their saturated analogs and polymers show strong fluorescence at the same chromophore concentration. This fluorescence structural self-quenching effect is attributed to an intramolecular charge transfer interaction. The polymerizable double bonds play a key role in the structural self-quenching. The fluorescence structural self-quenching is strongly correlated with the interaction strength and spacer length between A and D units, and solvent properties. Emphasis is laid on a special class of vinyl monomers with strong electron-accepting ability, i.e., maleimides, and their synthesis, polymerization, and photochemical and photophysical properties. Various macromolecular architectures of maleimides are described in detail. Several practical applications exemplify the photochemical and photophysical behavior of these D/A monomers and their polymers.