Photoinduced Formation of Microscopic Ordering and Macroscopic Pattern in Spiropyran-Containing Polyacrylate−Tetraoctylammonium Bromide Films

In this study, photoisomerizable polyacrylate containing spiropyran moieties was synthesized. By taking advantage of the photoinduced structural transformations of the spiropyran moieties, photoinduced microscopic ordering and eventually macroscopic patterns were formed in the polymer films consisting of spiropyran-containing polyacrylate (SPPA) and tetraoctylammonium bromide (TOAB). The patterns thus obtained are composed of concentric rings, which alternatively consist of macroscopic convex ridges and concave valleys, with the former being amphormous phases and the latter being ordered mesomorphous ones. It was found that the open-ring protonated merocyanine (MC) form of the spiropyran moieties, which is triggered by UV illumination, was crucial to the formation of mesomorphous structure and macroscopic patterns for this polymer−surfactant system. It is possible that the interaction between the MC form and TOAB leads to the formation of the microscopic ordering and macroscopic pattern in the polymer−TOAB films. This photoinduced macroscopic patterning in solid polymer−surfactant system could offer a new way for modulating and/or fabricating ordered supramolecular structure in macroscopic dimension by using light as a trigger.