Optical diffractometry is proposed as a practical method of quantitatively analyzing the microscopic structural origins of a wide range of highly efficient and linearly polarized optical diffraction grating produced from holographic polymer-dispersed liquid crystal. The structure is organized by a spatially periodical distribution of submicrometer-scale liquid crystal (LC) droplets in a polymer matrix. Six independent Bragg diffraction spectra were obtained at two orthogonal polarization states at temperatures below, at, and above the nematic-to-isotropic phase transition point. These spectra were simultaneously analyzed by employing anisotropic diffraction theory under the restraint of a simple and widely useful structural model constructed on the basis of the previously reported microscopic observations. The refractive indices of spatially periodic LC- and polymer-rich phases were analyzed using Cauchy's equation as a function of optical wavelength. The present diffractometry was demonstrated for a variety of holographic structures, and the structural parameters were discussed such as the filling ratio of LC droplets to polymer matrix, the orientational order in the droplets, and the thermo-optic properties in the LC droplets. Furthermore, the higher order Bragg diffractions were measured and discussed. The proposed method was examined in consistency by comparisons with polarizing optical microscopy and scanning electron microscopy.
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http://dx.doi.org/10.1103/PhysRevE.86.061701 | DOI Listing |
Polymers (Basel)
January 2025
Department of Physics, Washington State University, Pullman, WA 99163, USA.
This work aims to determine the mechanism of the photomechanical response of poly(Methyl methacrylate) polymer doped with the photo-isomerizable dye Disperse Red 1 using the non-isomerizable dye Disperse Orange 11 as a control to isolate photoisomerization. Samples are free-standing thin films with thickness that is small compared with the optical skin depth to assure uniform illumination and photomechanical response throughout their volume, which differentiates these studies from most others. Polarization-dependent measurements of the photomechanical stress response are used to deconvolute the contributions of angular hole burning, molecular reorientation and photothermal heating.
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January 2025
Department of Organic Chemistry and Technology, Faculty of Chemical Technology and Biotechnology, Budapest University of Technology and Economics, Műegyetem rkp. 3., 1111 Budapest, Hungary.
A series of α-hydroxy-alkylphosphonates and α-hydroxy-alkylphosphine oxides were synthesized by the Pudovik reaction of acetaldehyde and acetone with dialkyl phosphites or diarylphosphine oxides. The additions were performed in three different ways: in liquid phase using triethylamine as the catalyst (1), on the surface of AlO/KF solid catalyst (2), or by a MW-assisted NaCO-catalyzed procedure (3). In most of the cases, our methods were more efficient and more robust than those applied in the literature.
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January 2025
Department of Chemistry, University of Connecticut, Storrs, CT 06269, USA.
Optically responsive materials are applied in sensing, actuators, and optical devices. One such class of material is dye-doped liquid crystal polymers that self-assemble into cholesteric mesophases that reflect visible light. We report here the synthesis and characterization of a family of linear and mildly crosslinked terpolymers prepared by the ROMP of norbornene-based monomers.
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January 2025
Department of Information Display, Kyung Hee University, Seoul 02447, Republic of Korea.
In this paper, we demonstrate a blazed phase grating to achieve tunable beam steering and propose a novel algorithm to reduce the stripe noise in wrapped phase. To control the diffraction angle to steer light to the desired direction, an electrically tunable transmission-type beam deflector based on liquid crystals is introduced, and electric fields are applied to the patterned indium tin oxide electrodes to change its phase retardation. Two different 2π phase-wrapping methods are applied to obtain various diffraction angles within the minimum cell-gap, and the method of equal interval of phase achieves a worthwhile diffraction efficiency compared to the methods based on equal interval of diffraction angle.
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January 2025
Division of Smart Construction and Environmental Engineering, Daejin University, Pocheon 11159, Republic of Korea.
This study investigates the quality characteristics and healing performance of precast concrete incorporating self-healing technology, with the aim of supporting smart city implementation. To enhance the self-healing capabilities of concrete, hybrid self-healing capsules, combining solid capsules and liquid capsules, were utilized, and their applicability and practicality were assessed. The findings revealed that incorporating hybrid self-healing capsules into precast concrete resulted in a reduction in slump by up to 14% and air content by up to 9%.
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