Bernard J. Bulkin

Vibrational Spectra of Liquid Crystals. I. Changes in the Infrared Spectrum at the Crystal–Nematic Transition

The infrared spectra of 4,4′‐bis(alkoxy) azoxybenzenes (methyl, ethyl, butyl, pentyl, and hexyl) have been examined as a function of temperature through the crystal–nematic transition. Several bands are observed to disappear gradually as this transition is approached. The nature of these vibrational modes and the relative rates of their disappearance are discussed in terms of a lattice defect model of the crystal–nematic transition. Preliminary results for the crystal–smectic transition in 4,4′bis(heptyloxy) azoxybenzene are also reported.

Vibrational Spectra of Liquid Crystals. II. The Raman Spectrum of p‐Azoxyanisole in Crystal, Nematic, and Isotropic Phases, 10–100‐cm−1 Region

The Raman spectrum of p‐azoxyanisole has been observed in the crystal, nematic, and isotropic phases between 10 and 100 cm−1. The spectrum of an oriented single crystal at − 90°C shows that all 12 predicted lattice modes are found. In the polycrystalline sample, a soft mode is observed as the crystal–nematic transition is approached. The liquid crystal exhibits pseudolattice modes, which disappear in the isotropic melt. Assignments for the observed bands are discussed.

Raman spectroscopic study of human erythrocyte membranes

Abstract The Raman spectrum of human erythrocyte membranes in the 1000–1500 cm −1 region is reported. The results indicate the presence of considerable fluidity in the hydrocarbon chains of the phospholipids.

Vibrational Spectra of Liquid Crystals. VIII. Infrared Spectroscopic Measurements of Order in Nematics and Nematic Solutions

In an early study of the infrared spectrum of a nematic phase, Neff et. al. (1) used infrared dichroism to examine the effect of an electric field on the intensity of the CN stretching vibration in 4-methoxybenzylidene-4′-cyanoaniline. The dichroic ratios were used to obtain values of the order parameter as a function of field strength.

Vibrational Spectra of Liquid Crystals VI. Relative Intensities in Raman Spectra of Cholesteric and Nematic Solutions(1)

Abstract The Raman spectra of solutes in cholesteric solvents show differences in relative intensity from those in isotropic liquids. These are discussed in terms of a polarization scrambling model. Similar effects should be seen for solutes in some nematic phases. The intensity perturbations may occur for liquid crystal modes as well as for solute modes.

Vibrational Spectra of Liquid Crystals. VII. Infrared Spectra of Lecithin—Phosphatidyl Serine—Water Systems

Abstract Infrared spectroscopic studies of a mixed phospholipid-water system can be used to construct the phase diagram for this system. The results show that a small amount of phosphatidyl serine (PS) causes an inordinately large depression in the liquid crystal phase transition temperature. Results at higher concentrations of PS are also presented.

Lipid-protein interactions.I. Role of divalent ions in binding of glycylglycine to phosphatidylserine

Abstract The reaction between glycylglycine, divalent metals, and phosphatidylserine has been investigated. Calcium is unique among eight ions in forming a mixed lipid-dipeptide-Ca 2+ complex exclusively. The pH dependence of complex formation and results for all eight ions are reported.

Infrared Spectroscopic Measurements on the Crystal-Nematic Transition

Although many studies have been carried out to measure the extent of order as a function of temperature in the liquid crystalline state of thermotropic liquid crystals, little work has been done to indicate the amount of order or disorder in solids as the liquid crystalline state is approached. Such studies as have been reported (1), mainly deductions based on the shape of thermal analysis curves in the pre transition region, indicate that the crystal-nematic transition maybe of greater than first order or that there maybe some pre-transition phenomena. The shapes of DTA and DSC curves are, however, very dependent on instrumental response, etc., often in ways which have yet to be fully explored.

Raman Spectroscopy for the Study of Nematic Liquid Crystals

Liquid crystals, primarily as a consequence of their potential electro-optic applications, have attracted considerable scientific interest in the past decade. This interest has extended to a large number of theoretical studies of the structure and properties of liquid crystals, as well as to a variety of spectroscopic techniques which nicely complement the theoretical work.

Anonmalous Spherulitic Crystallization from a Cholesteric Mesophase

Abstract A ring crystallization pattern has been observed for a mixture containing 80% cholesteryl nanoate −20% cholesteryl propionate. This is discussed in terms of a segregation of components originating in the smectic phase of the nanoate.