Photodriven, Flexural-Torsional Oscillation of Glassy Azobenzene Liquid Crystal Polymer Networks

• Published in: Advanced functional materials 2011-08, Vol.21 (15), p.2913-2918
• Main Authors: Lee, Kyung Min, Smith, Matthew L., Koerner, Hilmar, Tabiryan, Nelson, Vaia, Richard A., Bunning, Timothy J., White, Timothy J.
• Format: Article
• Language: English
• Subjects: actuators; Amplitudes; Bending; Correlation; Glassy; Lasers; Liquid crystal polymers; liquid crystals; Networks; Oscillations; photochemistry; stimuli-responsive materials
• ISSN: 1616-301X; 1616-3028; 1616-3028
• DOI: 10.1002/adfm.201100333

Cantilevers composed of glassy, photoresponsive liquid crystalline polymer networks (LCNs) are shown to oscillate at high frequency (∼50 Hz) and large amplitude when exposed to light from a 442 nm coherent wave (CW) laser. Added dimensionality to previously reported in‐plane oscillations is enabled by adjusting the orientation of the nematic director to the long axis of the cantilever yielding in‐plane bending accompanied by out‐of‐plane twisting (flexural–torsional oscillation). The fundamental photoresponse of this class of glassy azobenzene liquid crystal polymer networks (azo‐LCN) is further probed by examining the influence of cantilever aspect ratio, laser intensity, and temperature. The frequency of photodirected oscillations is strongly correlated to the length of the cantilever while the amplitude and threshold laser intensity for oscillation is strongly correlated to temperature. Flexural–torsional oscillations consisting of in‐plane bending and out‐of‐plane twisting are observed in cantilevers composed of monodomain, photoresponsive liquid crystal polymers with the nematic director offset at intermediate angles to the long axis of the cantilever.