Reversible Photoinduced Twisting of Molecular Crystal Microribbons Lingyan Zhu Rabih O. Al-Kaysi Christopher J. Bardeen 10.1021/ja201925p.s001 https://acs.figshare.com/articles/journal_contribution/Reversible_Photoinduced_Twisting_of_Molecular_Crystal_Microribbons/2622762 9-Anthracenecarboxylic acid, a molecule that undergoes a reversible [4 + 4] photodimerization, is prepared in the form of oriented crystalline microribbons. When exposed to spatially uniform light irradiation, these photoreactive ribbons rapidly twist. After the light is turned off, they relax back to their original shape over the course of minutes. This photoinduced motion can be repeated for multiple cycles. The final twist period and cross-sectional dimensions of individual microribbons are measured using a combination of atomic force and optical microscopies. Analysis of this data suggests that the reversible twisting involves the generation of interfacial strain within the ribbons between unreacted monomer and photoreacted dimer regions, with an interaction energy on the order of 3.4 kJ/mol. The demonstration of reversible twisting without the need for specialized irradiation conditions represents a new type of photoinduced motion in molecular crystals and may provide new modes of operation for photomechanical actuators. 2011-08-17 00:00:00 generation Reversible Photoinduced Twisting photomechanical microribbon acid demonstration ribbon Molecular monomer combination actuators unreacted microscopie photodimerization type photoinduced motion mode strain uniform light irradiation kJ molecule Crystal data interaction photoreactive 3.4 analysis Microribbon crystal photoreacted dimer regions dimension