INVESTIGATION OF DIPOLAR ALIGNMENT OF MESOGENIC CHROMOPHORES IN SIDE-CHAIN LIQUID-CRYSTALLINE POLYSILOXANE USING ELECTRIC-FIELD-INDUCED 2ND-HARMONIC GENERATION

The behavior of the electric field induced dipolar alignment of mesogenic chromophores for a thin film of a side-chain liquid crystalline polysiloxane containing mesogenic NLO-active azo chromophores is investigated by UV-visible, polarized FTIR-ATR, variable-temperature FTIR, and second harmonic generation (SHG) measurements. This polymer exhibits a smectic C liquid crystalline phase from 59 to 113 degrees C, and the glass transition is observed near -19 degrees C. The mesogenic chromophores in the mesophase and the once-annealed solid were found to be aligned spontaneously nearly normal to the substrate (the homeotropic texture). When an electric field was applied to the once-annealed solid, a rapid increase in the SHG signal intensity was observed. It was shown that, under an electric field, the dipolar directions of the mesogenic chromophores would be easily aligned in the same direction in the once-annealed solid owing to the low T-g of the polymer, which indicates potential application for a room temperature SHG switching device.