偶氮苯介晶基元取向方式对其取向稳定性影响

根据取向透射率变化研究了偶氮苯侧链液晶聚合物在不同光照功率条件下的取向,用锥光干涉法表征了侧链介晶基元的取向方向,并研究了升温对取向膜的稳定性影响.实验结果表明介晶基元的取向速度和取向度都随光照时间和光照功率增加而增加|超过一定阈值功率（20 mW/cm2）时,随着光照时间延长薄膜的透射率（取向度）反而降低.高功率光照使侧链介晶基元发生了面内和面外两种取向,面外取向使聚合物膜的透射率降低.面外倾斜取向的介晶基元不稳定,在取向未达到饱和时停止光照,倾斜取向的介晶基元容易发生解取向,而面内取向的介晶基元则能维持取向的状态.用不饱和取向的方法,在光照功率为 20 mW/cm2时,取向时间缩短为饱和取向的1/20,薄膜的取向度提高1.3倍.4 ms的一次曝光足以使聚合物膜产生可读出、稳定的面内取向,取向的结果能保持2年不发生变化.

Orientation Mode of Azobenzene Mesogens and Their Effects on the Orientation Stability

 Out-of-plane and in-plane reorientations of mesogens were observed upon a linearly polarized light irradiation of azobenzene containing side-chain liquid crystalline polymer,which were characterized by the transmission various and polarized optical microscopy observation of the pumped film.Higher power density polarized light (20 mW/cm2) irradiation on the film induces that a maximal value of the photoinduced transmission is firstly obtained and then a decrease in the transmission value was observered.This suggests an out-of-plain orientation happened.Out-of-plane orientation decreases the stability of the oriented mesogens,which is confirmed by the lost of the anisotropy when the exposure light turn-off.The in-plane and out-of-plane reorientation depend on the laser fluence.The photoinduced anisotropy measurements results reveal that a stable orientation occurred by using an unsaturated irradiation upon a low power density laser beam.The unsaturated irradiation enables to shorten 95% of the incident time and increases the orientation order 1.3 times as compared to that of full orientation.A quick and high stable bit recording is achieved by unsaturated orientation upon 4 ms light irradiation.