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 mesoge nic chromophores for a thin film of a side-chain liquid crystalline po lysiloxane containing mesogenic NLO-active azo chromophores is investi gated by UV-visible, polarized FTIR-ATR, variable-temperature FTIR, an d second harmonic generation (SHG) measurements. This polymer exhibits a smectic C liquid crystalline phase from 59 to 113 degrees C, and th e glass transition is observed near -19 degrees C. The mesogenic chrom ophores 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 soli d, a rapid increase in the SHG signal intensity was observed. It was s hown that, under an electric field, the dipolar directions of the meso genic chromophores would be easily aligned in the same direction in th e once-annealed solid owing to the low T-g of the polymer, which indic ates potential application for a room temperature SHG switching device .