Allen Bloom

Use of carbon dioxide in energy storage

We have investigated an energy‐storage cycle in which CO2 is electrochemically reduced to formic acid, HCOOH. The product can be used in several ways. By means of a catalyst, it can be converted to hydrgen for use as a fuel or raw material. We have obtained data on the efficiency of the process and analyzed the energetics.

The Effect of Dye Structure on Order Parameter in a Nematic Liquid Crystalline Host1

Abstract The order parameters (S) of a number of substituted azobenzenes and phenylazothiazole, -benzothiazole and -heterocyclic compounds dissolved in a nematic liquid crystalline host have been determined. The measured order parameters for a class of azo compounds bear a strong relationship to the structure of the dye. For azobenzenes, there is an additivity of substituent effects which leads to good agreement between empirically-derived and observed S values. Disazo dyes give higher S values than the corresponding monoazo dyes. For heterocyclic phenylazo dyes, the end group substituents on the phenyl ring play a significant role in influencing S, whereas the nature of the heterocyclic system, as well as the end group substituents on the heterocyclic ring, are only of minor importance. The presence of an N-H moiety as part of a heterocyclic ring, or the fusion of a benzene ring onto a heterocyclic ring, can lead to significant changes in the order parameter.

Organic recording medium for volume‐phase holography

A new organic recording medium for volume‐phase holography is described. Holograms can be read out nondestructively at the recording wavelength and power. Self‐erasure may also be obtained. Holographic data and the effect of structure on recording and fixing behavior are described. The recording medium may be used to record multiple holograms.

The Effect of Host on Pleochroic Dye Order Parameter

Abstract The order parameters of three dyes in seven nematic liquid crystalline hosts have been measured. A correlation between a dyes length and its order parameter could be seen. Variations of as much as 50% in a dyes order parameter occurred on changing host.

Multiple storage of holograms in an organic medium

The multiple storage of volume phase holograms in samples of camphorquinone in an acrylic polyester is discussed.

Criteria for evaluating pleochroic dye liquid-crystal displays

Pleochroic dye liquid-crystal displays are generally characterized by the order parameter (S) or the contrast ratio (CR) of the dye at its absorption maximum. In this paper, we show the pitfalls of relying on these criteria. Instead, we introduce a descriptor that includes the relative spectral efficiencies for photopic vision that does correlate with viewer preferences. In addition, we delineate dye properties that are important for display applications.

Volume holographic recording characteristics of an organic medium

Volume holographic recording characteristics of camphorquinone in a rigid, acrylic polyester host are presented and related to the observed photoinduced refractive index changes. The dependence of the holographic recording on camphorquinone concentration, temperature, and light intensity is discussed in detail. The holograms are permanent and develop to their final efficiency slowly at room temperature. Heating after exposure can be used to accelerate fixing of the hologram.

Nonpolymeric organic host for recording volume phase holograms

Sucrose benzoate has been used as a host for recording volume phase holograms. Diffraction efficiencies up to 75% are obtained using a variety of photosensitive guests. Fixed or self‐erasing holgrams can be obtained.

Order Parameters of Schiff Base Azo Dyes in Nematic Liquid Crystalline Hosts

Abstract The order parameter (S) of a number of Schiff base azo compounds having the structure where Ar = 4-cyanophenyl, 4-nitrophenyl, 5-chlorothienyl, or2-pyridyl; Y = hydrogen, methyl, or methoxy; R = methyl, ethyl, n-butyl, or n-hexyl; NR2 = N-pyrrolidinyl have been determined in two different nematic liquid crystalline hosts both of which have a positive dielectric anisotropy. The results are discussed in terms of the effects of the dye structure on the order parameter.