Azobenzene-Containing Side-Chain Ionic Metathesis Polymers: Facile Synthesis, Self-Assembly And Photoresponsive Behavior

A series of well-defined azobenzene-functionalized ionomers were produced via ring-opening metathesis polymerization of norbornene-dicarboximide tethered to an ionic group further connected with an azobenzene unit in ionic liquid. The corresponding azobenzene-containing non-ionic polymers were also synthesized by the similar method. All the polymerizations were confirmed to be the characteristic of living based on the linear relationship between molecular weight and feed ratio. As expected, the distinct photoresponsive properties from azobenzene units in ionomers were observed under alternating irradiation of UV and visible light, which cannot be achieved by traditional azobenzene-containing non-ionic polymers. The ability and efficiency of trans -cis photoisomerization was depressed to some extent due to the presence of ionic groups nearby azobenzene units. Moreover, the sizes and morphologies of these ionomers can be modulated through changing the number of the methylene spacer to generate regular and uniform spherical nanostructures, ultimately leading to the unique photoisomerization behaviors. All these interesting results will not only provide a facile and efficient method for constructing photosensitive ionic metathesis polymers, but also expand the optical properties and application prospect of azobenzene-containing polymers.