Mechanism of thermal phase transition of a ferroelectric liquid crystal with monotropic transition temperature studied by infrared spectroscopy combined with principal component analysis and sample-sample two-dimensional correlation spectroscopy.

摘要: Infrared (IR) spectra of FLC-154 (FLC: ferroelectric liquid crystal) with monotropic phase transition under a nonalignment state sample layer thickness 24.5 microm were measured for heating process from 55 to 90 degrees C and cooling in increments 1 C. The thermal dynamics investigated by use IR spectroscopy combined principal component analysis (PCA) sample-sample two-dimensional (2D) correlation spectroscopy. During the cooling, molecule passes through smectic-C* (Sm-C*) phase, which is transformed Sm-A phase. results PCA suggest that during process, alkyl chains, core moiety, C=O groups are similar each other. Furthermore, 2D indicate chains chiral moieties responsible emergence Sm-C* This conclusion very important because data have given more evident cause than theoretical models such as molecular-statistical theory ordering indigenous polarization theory. Moreover, it has been found some trans conformations change partly gauche conformation when crystalline occurs. It also intermolecular interactions group moiety weaker those conformational occurs on C-O-C bonds upon going