Macrocycle-based topological azo-polymers: facile synthesis and unusual photoresponsive properties
Three kinds of well-defined topological azo-polymers with controlled molecular weights are prepared using an acrylate-functionalized cyclic polymeric azo-precursor by a selective head-to-tail acyclic diene metathesis (ADMET) polymerization. First, a multifunctional linear precursor bearing the terminal alkyne, hydroxyl, and azido groups were elaborately synthesized. A well-defined acrylate-containing monocyclic azo-polymer was then prepared via “click” ring closure and esterification, which can be considered a selective macromolecular chain stopper in the subsequent ADMET polymerizations of three different types of azo-functionalized monomers. Finally, azo-polymers with cyclic–linear, cyclic–linear–cyclic, and cyclic–hyperbranched topologies were successfully constructed, respectively. Interestingly, these prepared azo-polymers show distinct and unusual photoresponsive behaviors.