Zwitterion Interlocked Diarylethene Molecules Order, Unconnected Diarylethene Molecules Disorder

A diarylethene-based zwitterionic molecule (DZM) is newly synthesized for the development of smart films exhibiting reversible color change and switchable ionic conductivity in response to external light stimuli. This dual molecular building block is constructed through zwitterionic interlocking and strong phase separation between the dendron-shaped aliphatic tails and the diarylethene head. Uniaxial shear coating and molecular self-assembly result in anisotropically oriented nanostructures, which are further solidified through photopolymerization. In the absence of zwitterionic interlocking, DZM fails to form ordered structures and remains disordered. The anisotropically oriented nanostructures of DZM exhibit polarization-dependent photochromic properties despite the inherent low anisotropy of a single diarylethene chromophore. Structural analysis reveals that the zwitterion-interlocked molecular building block self-assemble into nanocolumns that align uniaxially during the shear coating process. Alternating ultraviolet and visible light reversibly switches the ionic conductivity of the DZM thin film and a change in color is observed due to the photoisomerization of the diarylethene chromophore. Utilizing the polarization-dependent photochromic properties, light-sensitive smart thin films are demonstrated with potential applications in anti-counterfeiting labels and sensors.