Synthesis and Characterization of Coumarin-Containing Cyclic Polymer and Its Photoinduced Coupling/Dissociation

Cyclic polystyrene (PS) with a pendant coumarin group is prepared by the combination of atom transfer radical polymerization and click chemistry. Fluorescence resonance energy transfer process is observed in the fluorescence measurement of coumarin-containing PS, and cyclic PS exhibits stronger emission than that of its linear precursor. When cyclic PS is irradiated under UV light at lambda = 365 nm, 8-shaped PS is achieved due to the dimerization of pendant coumarin group. Subsequently, 8-shaped PS can be divided into single macrocycle under UV irradiation at lambda = 254 nm via the photocleavage of coumarin dimer. The photoinduced coupling and dissociation are monitored by UV/vis spectra and gel permeation chromatography (GPC).