ALIGNMENT PHOTOREGULATION OF LIQUID-CRYSTALS ON PRECISELY AREA CONTROLLED AZOBENZENE LANGMUIR-BLODGETT MONOLAYERS

Single Langmuir-Blodgett monolayers of an azobenzene (Az) side chain a mphiphilic polymer are prepared with various monolayer areas ranging f rom 0.30 to 1.20 nm2 per Az unit at the air-water interface. Alignment photoregulation of a nematic liquid crystal (LC) is investigated usin g these precisely area controlled Az layers. It is newly found here th at photoresponding behaviours, such as (i) the magnitude of tilt angle changes, (ii) the in-plane orientation of LC molecules with respect t o the dipping direction on UV irradiation, and (iii) the reorienting b ehaviours effected by the polarized UV light, are influenced by the Az packing density in crucial ways. On the basis of the above LC respons e behaviours, the Az monolayer can be categorized into four area regio ns that should be of particular importance in the understanding and de sign of photo-commanding Az layers.