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Show moreQuadrupolar and octupolar invariants may be used as methods to attain noncentrosymmetric materials for application in second order nonlinear optics. The structure-property relationships for the J = 2, or quadrupole rotational invariant, are investigated. Proper citation for the Technical Digest CD-ROM should be written in the following format: Ostrovekhov V., Ostroverkhova O., Petschek R.G., Singer K.D., Sukhomlinova L., Twieg R.J., “`Quadrupolar' molecular nonlinear optics,” in the Conference on Lasers and Electro-Optics (CLEO)/The International Quantum Electronics Conference (IQEC) (Optical Society of America, Washington, DC, 2009), Proceedings, 8-9
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Show moreWe investigated 1:1 mixtures of a variety of 4,4′-disubstituted diphenyldiacetylenes (PTTP series) and cyano-containing mesogens for possible complex formation Complexes were formed when alkyl/alkoxy cyanobiphenyls (CB series) were mixed with alkyl/alkoxy PTTP homologues. We found complexes having a melting temperature higher than that for either component, and complexes with lower melting temperatures. A fluoro substituent on the PTTP gave an enhanced nematic phase and a cyclohexane ring in place of a benzene ring yielded an enhanced smectic A phase, but a cyano on the PTTP gave poor liquid crystalline properties. Phase diagrams were constructed for PTTP-24/5-CB and PTTP-24/8O-CB mixtures. Both complexes formed had melting temperatures higher than those for either component. These complexes were recrystallized and shown by X-ray studies to be 1:1 complexes. The PTTP-24/5-CB complex showed only a monotropic nematic phase, but the PTTP-24/8O-CB complex showed induced smectic A and hexatic B phases in addition to an enantiotropic nematic phase. ©1999 Taylor & Francis Ltd.
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Show moreOrganic chromophores have been exploited for a wide range of discrete optical and electronic functions as well as a growing number of combined opto-electronic functions. We are pursuing development of organic and polymer materials for a range of applications that require properties including liquid crystallinity, second order optical nonlinearity, photorefractivity and, more recently, special nonlinear optical behavior involving molecular chirality. On publication the full bibliographical details of the paper (Proceedings 561(1999), 119-130) must be inserted after the journal title, along with a link [http://journals.cambridge.org/abstract_S1946427400208403] to the Cambridge website address for the journal. Inclusion of this version of the paper in Institutional Repositories outside of the institution in which the contributor worked at the time the paper was first submitted will be subject to the additional permission of Cambridge University Press (not to be unreasonably withheld).
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Show moreSecond-order nonlinear optical (NLO) polymers, which polymers are functionalized with second-order NLO chromophores, offer advantages of large susceptibilities, high laser damage threshold, faster response time, a high density of NLO moieties, versatility of molecular structural modifications, improved processability and relatively higher thermal stability compared with small molecular weight organic materials. The design, synthesis and characterization of novel elastic-polymer containing NLO chiral conjugated chromophores based on the derivatives of chiral camphorquinone, which would be expected to display large three dimensional polarity and more thermal stable NLO optical materials are discussed.
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Show moreThe optical retardation of a liquid crystal above the nematic-isotropic phase transition temperature TNI and subjected to planar alignment conditions at the substrate was investigated in the presence of an electric field applied normal to the substrates. The response was found to exhibit "S"-shaped behavior with electric field, and was larger near TNI than well above TNI. The results were examined in the context of a model that permits both biaxiality and a field-induced tilt of the molecular director. The results suggest that the primary effect of the electric field is to induce biaxiality, and in consequence suppress the order induced by the surface. No clear indication of a Freedericksz-like transition, either experimental or theoretical, was observed. Appropriate bibliographic citation and notice of the APS copyright must be included- "Kim J.-H., Petschek R.G., Rosenblatt C., Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 60:0.208333333333333, 5600-5606 (1999). Copyright 1999 by the American Physical Society."
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Show moreIn this paper we develop a self-consistent model for the equilibrium statistics of nematic branched polymeric liquid crystals in the mean-field approximation. We have solved the resulting system of equations numerically and find a nematic-isotropic phase transition. We find that the order-disorder transition temperature scales as a function of the bond continuation probability, or equivalently the molecular weight, with an exponent that depends on the interaction potential. These results are compared with the experimentally observed behaviour. ©1999 Taylor & Francis Ltd.
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Show moreIn a previous article [Phys. Rev. E 60, 1799 (1999)], the authors considered a model Landau free energy that explained the ferriclinic phases of chiral smectic liquid crystals as a series of short period helical modulations. In this paper we begin with a physically more realistic, more microscopic interlayer free energy and show how our previous work can be derived using only simple short-ranged interactions. We then discuss what additional information this provides about the Landau coefficients used previously to construct the phase diagram for the heliclinic phases of chiral smectic liquid crystals. Finally, we investigate a means for explicitly including chirality in our model. Appropriate bibliographic citation and notice of the APS copyright must be included- "Stott J.J., Petschek R.G., Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 60:0.25, 6826-6830 (1999). Copyright 1999 by the American Physical Society."
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Show moreStatic light scattering and electric field-induced Kerr measurements were performed above the nematic-isotropic phase transition of a terminal-lateral-lateral-terminal negative Poisson ratio trimer. For both measurements the inverse susceptibility was observed to be nearly linear with temperature, a result inconsistent with our previously reported Kerr data [Phys. Rev. E 58, 2041 (1998)]. Appropriate bibliographic citation and notice of the APS copyright must be included- "Kang D., Mahajan M.P., Zhang S., Petschek R.G., Rosenblatt C., He C., Liu P., Griffin A.C., Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 60:4 B, 4980-4982 (1999). Copyright 1999 by the American Physical Society."
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Show moreThe formation of double-twisted helix in achiral liquid crystal and isoregic chiral smectic C polyesters is presented. Mixing chlorinated and the non-chlorinated banana liquid crystals at an appropriate formulation have lowered the transition temperature of the switchable banana phase. The achiral liquid crystal exhibit a polarization of 50 nC/cm2 in the switchable banana phase. The isoregic chiral polyesters exhibit a smectic C and A phases. Optoelectronic studies of the isoregic chiral smectic C polyesters require a well aligned sample, which the development of an improved methods is in progress.
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Show moreWe prepared a series of isoregic chiral smectic polyesters based on (R)-(-)-4′-{ω-[2-(p-hydroxy-o-nitrophenyloxy)-1-propoxy]-1-alkyloxy} -4-biphenylcarboxylic acid. The head-to-tail (p-hydroxybenzoic acid) type monomers enable us to proceed the isoregically controlled polycondensation. All the monomers exhibited the chiral smectic C and nematic mesophases. The isoregic chiral smectic polyesters have good thermal stability and exhibit monolayered chiral smectic C and smectic A structures. © 1999 American Chemical Society. Appropriate credit for the requested material should be given as follows: "Reprinted (adapted) with permission from Chemistry of Materials 11:7, 1666-1671. Copyright 1999 American Chemical Society."
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Show moreBy considering short period helical planar modulations about the layer normal, we construct a model free energy for the ferriclinic phases observed in chiral smectic liquid crystals. We then use this free energy to construct the phase diagram for our model. The resulting phases are compared with the experimentally observed smectic-C* subphases (ferroclinic, antiferroclinic, and heliclinic). A strong coupling is found between the ferroclinic q=2Ï€/a and the heliclinic q=2Ï€/3a modes. This coupling was not considered in previous models. The resulting additional stability of this "locked in" phase is discussed. © 1999 The American Physical Society. Appropriate bibliographic citation and notice of the APS copyright must be included- "Stott J.J., Petschek R.G., Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics 60:2 B, 1799-1807 (1999). Copyright 1999 by the American Physical Society."
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