Dynamic ft‐ir spectroscopy of polymer films and liquid crystals

The use of continuous‐scan and step‐scan Fourier transform infrared (FT‐IR) spectroscopic techniques to study the dynamics of the response of polymer films and liquid crystals to external perturbations is described here. The first application of dynamic stepscan FT‐IR deals with the response of various polymer films to sinusoidally modulated tensile strain. In these experiments, a small amplitude sinusoidal stress is applied to a polymeric film and the transition dipole responses are monitored as a phase lag with respect to the external perturbation. The degree of deformation is small enough to cause only linear reversible responses to the sample. The main advantage of the technique is that it can provide valuable information at the molecular level that can be used to interpret the macroscopic properties of the polymeric material under investigation. Results for heterogeneous polymers include semicrystalline high density/low density polyethylene blends and the micro‐phase separated copolymer Kratonr̀ are presented. In addition, continuous‐scan stroboscopic FT‐IR was used to explore the submolecular (functional group) contributions to the reorientation dynamics of the liquid crystal director in response to pulsed (DC) electric fields. For the nematic liquid crystal molecules, 4‐pentyl‐4'‐cyanobiphenyl (5CB) and 4‐pentyl‐4'‐cyanophenylcyclohexane (5PCH), the individual response of the rigid and floppy parts was examined. Copyright © 1995 Hüthig & Wepf Verlag

Duke Scholars

Author Richard A. Palmer Chemistry