Azobenzene-containing ionic metathesis copolymers: Composition, self-assembly and photoresponsive property

The properties of synthetic polymers are influenced by the connection mode of polymer chains even polymers made from the same monomer. In this work, the diverse composition systems of cyclooctene-based alternating, random and block azo-copolymers containing imidazolium cation units as side group were successfully achieved based on different metathesis methods in the ionic liquid with good control over the polymerization processes. All these ionic azo-copolymers were tailored to explore the effects of monomers sequences and non-covalent interactions on photoresponsive behaviors and self-assembly morphologies. Since the special alternating structure, UV-light-triggered the shackling trans-*cis photoisomerization transition was observed, ultimately spontaneously forming highly regular and uniform polymer vesicle with recoverable size variation in THF directly. Differently, the micellar characterization was carried out by the self-assembly of ionic block azo-copolymers in a selective solvent of toluene to obtain spherical micelle with reversible shape evolution considering nearly 86 % trans-*cis relative isomerization efficiency. These interesting results not only demonstrate the diversity of metathesis polymerization but also expand the property of azo-copolymers.