STUDY OF THE PHYSICAL-PROPERTIES OF AN ESTER BIPHENY, MIXTURE, EXHIBITING AN INJECTED SMECTIC PHASE, BY SMALL-ANGLE X-RAY-DIFFRACTION/

Small angle x-ray diffraction intensities from binary mixtures of 4-n- pentyl 4'cyanobiphenyl (5CB) and 4-n pentyl phenyl 4-n' hexyloxy benzo ate (ME60.5), which show an injected smectic phase, have been analysed to determine the orientational order parameters [P-2] and [P-4], the translational order parameter, the layer thickness in the smectic phas e, and the apparent molecular length in the nematic phase. The order p arameters have been fitted satisfactorily to those calculated from McM illan's theory by varying the potential parameters alpha and delta. Th e experimental variation of the layer thickness with mole fraction of 5CB has been explained fairly well by assuming the presence of both ho me dimers (5CB + 5CB) and hetero dimers (5CB + ME 60.5) in the mixture . Orientational order parameters, layer thickness, and packing fractio n all exhibit minima at about 50% molar concentration of 5CB.