Time-Resolved FT-IR Study of Electric-Field Induced Homogeneous-to-Homeotropic Transition of Nematic 4-Pentyl-4'-cyanobiphenyl

A time-resolved FT-IR study of electric-field induced homogeneous-to-homeotropic transition of nematic 4-pentyl-4'-cyanobiphenyl (5CB) is reported. A homogeneous 5CB sample exhibits a bond orientational order parameter S b =0.40 for the C ≡N stretching band and for the phenyl C–C stretching band, both polarized parallel to the para-axis of the cyanobiphenyl core. Transition to the homeotropic structure under a DC pulse field requires an induction period of ca. 5 ms, and takes place in the 5∼10 ms region. The potential applicability of the FT-IR time-resolved spectroscopy in the study of dynamic properties of liquid crystals is emphasized.