Raman Spectroscopic and Calorimetric Investigation of the Multiple Smectic Phase Material TBBA
Smectic mesophase formation and structure have been the subject of vigorous scientific inquiry in recent years. 1–6 Among those phases investigated most intensively, the B and H phases are thought to possess the highest degree of local three-dimensional order. As determined by X-ray crystallography 1–5 both phases exhibit long-range two dimensional pseudo-hexagonal order within each layer; in addition there appears to be some degree of correlation between planes.1,5 In the H phase the director lies at an angle to the smectic planes, while in the B phase it is normal to the planes. The nature of the degrees of freedom available and the intermolecular ordering in these phases has been the subject of a number of theoretical and experimental studies.3,7,8 Since terephthal-bis-butylaniline (TBBA) exhibits a smectic H phase as well as at least eight other phases (see schematic below), it has been extensively studied by various experimental techniques including X-ray,4 NMR,9 DSC,10 neutron scattering,11 infrared12 and Raman10,13–14 spectroscopy. This paper provides new information on the nature of the various smectic phases observed in TBBA.
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