Photoinduced Bending Behaviour of Cross-linked Liquid Crystalline Polymers with High Cross-linking Densities.doc


Photoinduced Bending Behaviour of Cross-linked Liquid
Crystalline Polymers with High Cross-linking Densities#
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Jiang Zhen, Lv Jiu-an, Chen futao, Wei Jia, Yu Yanlei**
(Department of Materials Science, Fudan University, Shanghai 200433, China.)
Abstract: In this paper, highly crosslinked liquid-crystalline polymer (CLCP) films with a longer
spacer and different locations and concentrations of azobenzene chromophores were prepared. The
dichroic ratios and the order parameters of the films were estimated from polarized UV absorbance.
The effects of various factors on the photoinduced bending behavior of this highly crosslinked CLCPs
were also explored. It was found that longer spacer and higher crosslinking density contributed to much
faster bending of the CLCP films than those reported in the literature with shorter spacer and lower
crosslinking density. The azobenzene chromophores at crosslinks affected the photoinduced bending
behavior of the CLCP films more significantly than those with the chromophores at side chains.
Furthermore, it was observed that the decrease on the concentration of the azobenzene chromophores
brought faster bending and larger photoinduced stress of the CLCP films containing the azobenzene
chromophores at side chains than those incorporated with the chromophores at the crosslinks. In
addition, the CLCP film with relatively low azobenzene concentration and thin thickness exhibited
bending towards reverse direction after bent to maximum extent by continuous irradiation with UV
light, showing that the photomobile behavior could be determined by proper design of the material
system.
Key words: azobenzene; liquid crystalline polymer; photoresponsive
0 Introduction
Materials that can adopt different shapes or volumes when exposed to stimuli, such as pH
variation, temperature, electric field, and light, have received widespread interest.[1] Light, a
clean source of energy, affords specific adv