Laser Raman Study of Terepthalylidene-bis-p-n-Decylaniline (TBDA)

Abstract

The Raman spectra of Terepthalylidene-bis-p-n-declyaniline (TBDA), have been recorded as a function of temperature in the temperature range from 55.0°C (solid) to 199.0°C (isotropic liquid) in the 1100–1200cm⁻¹ and 1520–1650cm⁻¹ regions. The precise values of peak positions, integrated intensities and linewidths of some selected Raman bands have been obtained by deconvoluting the bands. The changes in the molecular alignment and its effect on inter/intra molecular interactions at two particular phase transitions viz., solid-smectic G (K-S_G ) and smectic I-Smectic C (S_I-S_c ) have been discussed on the basis of variation in the Raman spectral parameters with temperature. From detailed considerations, it is inferred that the increased orientational/vibrational freedom of long alkyl chain on the core is responsible for major spectral changes at the K-S_G transition while the changes in the intramolecular interactions of the core part with increased fluidity, is responsible for spectral anomalies at the S_I-S_c transition.

Key Words:

• Liquid crystals
• Laser Raman spectroscopy
• molecular dynamics
• SI-Sc transition