Light-Induced High Frequency Oscillation of Aligned Azobenzene Liquid Crystalline Polymers

Photoactuators are attractive systems in which light energy is converted into motion. Previously, we reported the oscillatory behavior of cantilevers composed of glassy, azobenzene-functionalized liquid crystalline polymer networks (azo-LCNs). The azo-LCN cantilever containing 20% azobenene oscillates at high frequencies (50-120 Hz) and large amplitudes when exposed to light from a 442 nm coherent wave (CW) laser. The frequency of photoinduced oscillations was strongly affected by the aspect ratio of the cantilever, whereas the amplitude of the oscillation was affected by temperature. An azobenzene functionalized LC elastomer (azo-LCE) was prepared and the photoresponsive behavior is compared with the glassy azo-LCN. The glass transition temperature of azo-LCE is lower than room temperature. The fundamental photoresponses of these glassy and elastomeric azobenzene liquid crystal polymers (azo-LCN and azo-LCE) are further compared by examining the cantilever aspect ratio, laser intensity, and temperature. This photoinduced large bending and oscillation response of azo-LC polymers can be used for soft robotics and flow control.