2. Introduction
Although the LC mixtures composed of nematic or cholesteric liquid crystals (LCs) and azobenzene compounds have been comprehensively studied, the LC mixtures composed of smectic LC and the photoresponsive molecule are rarely reported.
・Experiment1
　Phase transitions in smectic LCs doped with the azobenzene AB
・Experiment2
Phase transitions in smectic LCs doped with a chiral molecule and the azobenzen AB
・Experiment 3
Effect of temperature on the photo-switching

3. Sample compounds

4. Photocromism of LC-A1(97% of 8 CB,3% of AB)
Figure shows the photoisomerizaiton of trans to cis(under UV irradiation, 21℃)

5. Phase transitions in smectic LCs doped with the azobenzen
Before UV
After UV(480s)
Before UV
After UV(480s)
a:LC-A1(3%AB)　　　　　 b:LC-A2(5%AB)　　　　　 c:LC-A3(7%AB) 　　　　d(10%AB)　21℃
・With the increase of the amount of the azobenzen, the smectic states 　　　　could be changed to nematic and isotropic states.(b and c).
・The smectic textures of the cells could be recoverd.

6. Phase transitions in smectic LCs doped with a chiral molecule and the azobenzene
LC-A1(96% of 8CB,1% of BD, 3% of AB) 28℃
・Change from smectic states to cholesteric states was observed by adding chiral dopants.

7. Isotropic phase could be recoverd to cholesteric and smectic phase
LC-A-B2
(89% of 8CB, 1% of BD, 10% of AB)
・After changed cholesteric states,recoverd smectic states by irradiating visible light.

8. Change of reflection wavelength by amount of chiral dopant
λ=nP
LC-A-B3
(92.5% of CB ,2.5% of BD, 5.0% of AB)
LC-A-B5
(90% of 8CB,5% of BD, 5% of AB)
・ The higher the concentration of chiral dopant, the smaller the helical pitch, and then the shorter the reflection wavelnegth.

9. Effect of temperature on the photo-switching
LC-A-B4
(92.5% of 8CB, 2.5% of BD, 5.0% of AB)
UV0s
UV120s
UV0s
UV60s
UV300s
UV480s
UV120s
UV300s
21℃
28℃
・A t28℃ the higher temperature resulted in the decrease of the order of the smectic 8CB and then the cholesteric phase formed before UV irradiation.

10. Effect of temperature on the photo-switching
LC-A-B4
(92.5% of 8CB, 2.5% of BD, 5.0% of AB)
21℃
28℃
・The trans isomers could be transformed into cis isomers more quickly at 28℃ under UV irradiation compared with the lower temperature 21℃.

11. Conclusion
・For the LC cells of 8 CB doped with the azobenzene compound AB, the smectic phase could be switched to nematic and then to isotoropic phase induced by the trans-to-cis photoisomerization of AB upon the UV irradiation.
・For the LC cells of 8CB doped with the azobenzene compound AB and a chiral compuond BD, the smectic phase could be switched to cholesteric and then to the isotoropic phase induced by the trans-to-cis photoisomerization of AB upon the UV irradiation.
・By adjusting the concentration of the azobenzene compound AB and chiral comopound BD and the temperature performed, the phase tarnsitions from smectic to nematic or to cholesteric and then to isotropic can be reversibly controlled by the UV and Vis irradiations.