Thermal, Optical, X-ray, Infrared and NMR'Studies on the a-phase of Some Saturated Aliphatic Esters

The paper reports the results of the investigations carried out from diverse aspects on the a-phase exhibited by ethyl, n-pmpyl and n-butyl stearates and mixtures of methyl stearate and palmitate, prior to their solidification into the crystalline 8-phase. Optical examination reveals the formation of stepped drops and facetted drops, indicating a high degree of molecular order in the a-phase. From the features observed in X-ray difTrtxtion, it emerges that the ct-phaso corresponds to the ordered smectic mesophase in which there is hexagonal cylindrical packing of the molecules in the smectic layers. Infrared absorption spectra also show that in the a-phase the zig-zag chaine of molecules me fully extended. In the u-phase, the existence of rotational motions of the molecules is revealed both by infiared and proton magnetic resonance studies.