1
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Jahnke JP, Kim D, Wildemuth DJ, Nolla J, Berkow MW, Gwak H, Neyshtadt S, Segal-Peretz T, Frey GL, Chmelka BF. Mesostructured Materials with Controllable Long-Range Orientational Ordering and Anisotropic Properties. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2306800. [PMID: 37849390 DOI: 10.1002/adma.202306800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 10/02/2023] [Indexed: 10/19/2023]
Abstract
Inorganic-organic mesophase materials provide a wide range of tunable properties, which are often highly dependent on their nano-, micro-, or meso-scale compositions and structures. Among these are macroscopic orientational order and corresponding anisotropic material properties, the adjustability of which are difficult to achieve. This is due to the complicated transient and coupled transport, chemical reaction, and surface processes that occur during material syntheses. By understanding such processes, general criteria are established and used to prepare diverse mesostructured materials with highly aligned channels with uniform nanometer dimensions and controllable directionalities over macroscopic dimensions and thicknesses. This is achieved by using a micropatterned semipermeable poly(dimethylsiloxane) stamp to manage the rates, directions, and surfaces at which self-assembling phases nucleate and the directions that they grow. This enables mesostructured surfactant-directed silica and titania composites, including with functional guest species, and mesoporous carbons to be prepared with high degrees of hexagonal order, as well as controllable orthogonal macroscopic orientational order. The resulting materials exhibit novel anisotropic properties, as demonstrated by the example of direction-dependent photocurrent generation, and are promising for enhancing the functionality of inorganic-organic nanocomposite materials in separations, catalysis, and energy conversion applications.
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Affiliation(s)
- Justin P Jahnke
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Donghun Kim
- School of Chemical Engineering, Chonnam National University, Gwangju, 61186, Republic of Korea
| | - Douglas J Wildemuth
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Jordi Nolla
- Institute for Advanced Chemistry of Catalonia, Spanish National Research Council (IQAC-CSIC), Carrer Jordi Girona 16-26, Barcelona, 08034, Spain
| | - Maxwell W Berkow
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Hosu Gwak
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
| | - Shany Neyshtadt
- Department of Materials Science and Engineering, Technion Institute of Technology, Haifa, 32000, Israel
| | - Tamar Segal-Peretz
- Department of Chemical Engineering, Technion Institute of Technology, Haifa, 32000, Israel
| | - Gitti L Frey
- Department of Materials Science and Engineering, Technion Institute of Technology, Haifa, 32000, Israel
| | - Bradley F Chmelka
- Department of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA, 93106, USA
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2
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Ettinger S, Slaughter CG, Parra SH, Kikkawa JM, Collings PJ, Yodh AG. Magnetic-field-driven director configuration transitions in radial nematic liquid crystal droplets. Phys Rev E 2023; 108:024704. [PMID: 37723717 DOI: 10.1103/physreve.108.024704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 07/21/2023] [Indexed: 09/20/2023]
Abstract
We study the director configurations of nematic liquid crystal (NLC) droplets with homeotropic anchoring in a magnetic field and report observation of a magnetic-field-driven transition from a deformed radial to an axial-with-defect configuration. Magnetic-field-induced transitions in NLC droplets differ fundamentally from the traditional planar Freedericksz transition due to the spherical droplet geometry and resulting topological defect. This transition has been studied theoretically, but the director configurations and mechanism of defect evolution in an applied magnetic field have yet to be observed experimentally. To this end, we combine polarized optical microscopy with a variable electromagnet (≤1 T) for continuous observation of droplet director fields, and we employ Landau-de Gennes numerical simulations to elucidate the director configurations and first-order nature of the transition. We report a configuration transition from point defect to ring defect at a critical field, which varies inversely with droplet radius and is relatively independent of surfactant type and concentration. We also estimate anchoring strengths of commonly used surfactants at the NLC-aqueous interface.
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Affiliation(s)
- Sophie Ettinger
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Charlotte G Slaughter
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Sebastian Hurtado Parra
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - James M Kikkawa
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Peter J Collings
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - A G Yodh
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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3
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Wu K, Sun W, Li D, Diao J, Xiu P. Inhibition of Amyloid Nucleation by Steric Hindrance. J Phys Chem B 2022; 126:10045-10054. [PMID: 36417323 DOI: 10.1021/acs.jpcb.2c06330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Despite recent experiments and simulations suggesting that small-molecule inhibitors and some post-translational modifications (e.g., glycosylation and ubiquitination) can suppress the pathogenic aggregation of proteins due to steric hindrance, the effect of steric hindrance on amyloid formation has not been systematically studied. Based on Monte Carlo simulations using a coarse-grained model for amyloidogenic proteins and a hard sphere acting as steric hindrance, we investigated how steric hindrance on proteins could affect amyloid formation, particularly two steps of primary nucleation, namely, oligomerization and conformational conversion into a β-sheet-enriched nucleus. We found that steric spheres played an inhibitory role in oligomerization with the effect proportional to the sphere radius RS, which we attributed to the decline in the nonspecific attractions between proteins. During the second step, small steric spheres facilitated the conformational conversion of proteins while large ones suppressed the conversion. The overall steric effect on amyloid nucleation was inhibitory regardless of RS. As RS increased, oligomeric assemblies changed from amorphous into sheet-like, structurally ordered species, reminiscent of the structure of amyloid fibrils. The oligomers with large RS were off-pathway with their ordered structures induced by the competition between steric hindrance and nonspecific attractions of soluble proteins. Interestingly, the equimolar mixture of proteins with and without steric hindrance amplified the sterically inhibitory effect by increasing the energy barrier of protein's conformational conversion. The physical mechanisms and biological implications of the above results are discussed. Our findings improve the current understanding of how nature regulates protein aggregation and amyloid formation by steric hindrance.
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Affiliation(s)
- Kai Wu
- Department of Engineering Mechanics, Zhejiang University, Hangzhou 310027, People's Republic of China.,School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.,Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou 325001, China.,Department of Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267, United States of America
| | - Wuxuepeng Sun
- Department of Engineering Mechanics, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - Dechang Li
- Department of Engineering Mechanics, Zhejiang University, Hangzhou 310027, People's Republic of China
| | - Jiajie Diao
- Department of Cancer Biology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267, United States of America
| | - Peng Xiu
- Department of Engineering Mechanics, Zhejiang University, Hangzhou 310027, People's Republic of China
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4
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Mesoscale Anisotropy in Porous Media Made of Clay Minerals. A Numerical Study Constrained by Experimental Data. MATERIALS 2018; 11:ma11101972. [PMID: 30322150 PMCID: PMC6212813 DOI: 10.3390/ma11101972] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 10/11/2018] [Accepted: 10/12/2018] [Indexed: 11/16/2022]
Abstract
The anisotropic properties of clay-rich porous media have significant impact on the directional dependence of fluids migration in environmental and engineering sciences. This anisotropy, linked to the preferential orientation of flat anisometric clay minerals particles, is studied here on the basis of the simulation of three-dimensional packings of non-interacting disks, using a sequential deposition algorithm under a gravitational field. Simulations show that the obtained porosities fall onto a single master curve when plotted against the anisotropy value. This finding is consistent with results from sedimentation experiments using polytetrafluoroethylene (PTFE) disks and subsequent extraction of particle anisotropy through X-ray microtomography. Further geometrical analyses of computed porous media highlight that both particle orientation and particle aggregation are responsible of the evolution of porosity as a function of anisotropy. Moreover, morphological analysis of the porous media using chord length measurements shows that the anisotropy of the pore and solid networks can be correlated with particle orientation. These results indicate that computed porous media, mimicking the organization of clay minerals, can be used to shed light on the anisotropic properties of fluid transfer in clay-based materials.
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5
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Davis-Purcell B, Soulard P, Salez T, Raphaël E, Dalnoki-Veress K. Adhesion-induced fingering instability in thin elastic films under strain. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2018; 41:36. [PMID: 29564573 DOI: 10.1140/epje/i2018-11643-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 02/28/2018] [Indexed: 06/08/2023]
Abstract
In this study, thin elastic films supported on a rigid substrate are brought into contact with a spherical glass indenter. Upon contact, adhesive fingers emerge at the periphery of the contact patch with a characteristic wavelength. Elastic films are also pre-strained along one axis before the initiation of contact, causing the fingering pattern to become anisotropic and align with the axis along which the strain was applied. This transition from isotropic to anisotropic patterning is characterized quantitatively and a simple model is developed to understand the origin of the anisotropy.
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Affiliation(s)
- Benjamin Davis-Purcell
- Department of Physics & Astronomy, McMaster University, Hamilton, L8S 4M1, Ontario, Canada
| | - Pierre Soulard
- Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 10 rue Vauquelin, 75005, Paris, France
| | - Thomas Salez
- Univ. Bordeaux, CNRS, LOMA, UMR 5798, F-33405, Talence, France
- Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan
| | - Elie Raphaël
- Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 10 rue Vauquelin, 75005, Paris, France
| | - Kari Dalnoki-Veress
- Department of Physics & Astronomy, McMaster University, Hamilton, L8S 4M1, Ontario, Canada.
- Laboratoire de Physico-Chimie Théorique, UMR CNRS Gulliver 7083, ESPCI Paris, PSL Research University, 10 rue Vauquelin, 75005, Paris, France.
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6
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Guin T, Kowalski BA, Rao R, Auguste AD, Grabowski CA, Lloyd PF, Tondiglia VP, Maruyama B, Vaia RA, White TJ. Electrical Control of Shape in Voxelated Liquid Crystalline Polymer Nanocomposites. ACS APPLIED MATERIALS & INTERFACES 2018; 10:1187-1194. [PMID: 29239172 DOI: 10.1021/acsami.7b13814] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Liquid crystal elastomers (LCEs) exhibit anisotropic mechanical, thermal, and optical properties. The director orientation within an LCE can be spatially localized into voxels [three-dimensional (3-D) volume elements] via photoalignment surfaces. Here, we prepare nanocomposites in which both the orientation of the LCE and single-walled carbon nanotube (SWNT) are locally and arbitrarily oriented in discrete voxels. The addition of SWNTs increases the stiffness of the LCE in the orientation direction, yielding a material with a 5:1 directional modulus contrast. The inclusion of SWNT modifies the thermomechanical response and, most notably, is shown to enable distinctive electromechanical deformation of the nanocomposite. Specifically, the incorporation of SWNTs sensitizes the LCE to a dc field, enabling uniaxial electrostriction along the orientation direction. We demonstrate that localized orientation of the LCE and SWNT allows complex 3-D shape transformations to be electrically triggered. Initial experiments indicate that the SWNT-polymer interfaces play a crucial role in enabling the electrostriction reported herein.
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Affiliation(s)
- Tyler Guin
- Air Force Research Laboratory, Materials and Manufacturing Directorate , 3005 Hobson Way, Wright-Patterson AFB, Ohio 45433-7750, United States
- Azimuth Corporation , 4027 Colonel Glenn Highway, Beavercreek, Ohio 45431, United States
| | - Benjamin A Kowalski
- Air Force Research Laboratory, Materials and Manufacturing Directorate , 3005 Hobson Way, Wright-Patterson AFB, Ohio 45433-7750, United States
- Azimuth Corporation , 4027 Colonel Glenn Highway, Beavercreek, Ohio 45431, United States
| | - Rahul Rao
- Air Force Research Laboratory, Materials and Manufacturing Directorate , 3005 Hobson Way, Wright-Patterson AFB, Ohio 45433-7750, United States
| | - Anesia D Auguste
- Air Force Research Laboratory, Materials and Manufacturing Directorate , 3005 Hobson Way, Wright-Patterson AFB, Ohio 45433-7750, United States
| | - Christopher A Grabowski
- Air Force Research Laboratory, Materials and Manufacturing Directorate , 3005 Hobson Way, Wright-Patterson AFB, Ohio 45433-7750, United States
- UES, Inc. , 4401 Dayton Xenia Rd, Beavercreek, Ohio 45432, United States
| | - Pamela F Lloyd
- Air Force Research Laboratory, Materials and Manufacturing Directorate , 3005 Hobson Way, Wright-Patterson AFB, Ohio 45433-7750, United States
- UES, Inc. , 4401 Dayton Xenia Rd, Beavercreek, Ohio 45432, United States
| | - Vincent P Tondiglia
- Air Force Research Laboratory, Materials and Manufacturing Directorate , 3005 Hobson Way, Wright-Patterson AFB, Ohio 45433-7750, United States
- Azimuth Corporation , 4027 Colonel Glenn Highway, Beavercreek, Ohio 45431, United States
| | - Benji Maruyama
- Air Force Research Laboratory, Materials and Manufacturing Directorate , 3005 Hobson Way, Wright-Patterson AFB, Ohio 45433-7750, United States
| | - Richard A Vaia
- Air Force Research Laboratory, Materials and Manufacturing Directorate , 3005 Hobson Way, Wright-Patterson AFB, Ohio 45433-7750, United States
| | - Timothy J White
- Air Force Research Laboratory, Materials and Manufacturing Directorate , 3005 Hobson Way, Wright-Patterson AFB, Ohio 45433-7750, United States
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7
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Hu H, Rey AD. Multi-step modeling of liquid crystals using ab initio molecular packing and hybrid quantum mechanics/molecular mechanics simulations. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2017. [DOI: 10.1142/s0219633617500122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A density functional theory (DFT) based multi-step simulation method is used to characterize the detailed molecular structure and inter/intra- molecular interactions of two benchmark liquid crystals (LC) 5CB, 8CB and a novel tri-biphenyl ring bent core LC material. The method uses hybrid DFT at the B3LYP/6-31G* level to obtain molecular structure and Raman data. These results are fed to a crystal packing simulation to find possible crystal structures. A pico-second quantum mechanics/molecular mechanics (QM/MM) simulation model is built for the selected structures with lower overall energy as well as optimal density. The stabilized crystal structures are then extended into a super cell, heated and simulated using a mixed force field and nano-second molecular dynamics (MD). The described simulation process sequence provides predictions of molecular Raman spectrum, LC density, isotropic depolarization ratio, ratio of differential polarizability, order parameters, molecular structures, and rotating Raman spectrum of the different mesophases. The Raman spectra, order parameters and depolarization ratios all agree well with existing experimental and previous simulation results. The study of the novel tri-biphenyl ring bent core LC system shows that the ratio of differential polarizability depends on intra-molecular interactions. The findings presented in this manuscript contribute to the on-going efforts to establish links between LC molecular structures and their properties, including optical behavior.
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Affiliation(s)
- Hang Hu
- Department of Chemical Engineering, McGill University, H3A 0G4, Montreal, Canada
| | - Alejandro D. Rey
- Department of Chemical Engineering, McGill University, H3A 0G4, Montreal, Canada
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8
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Singh G, Fu J, Agra-Kooijman DM, Song JK, Vengatesan MR, Srinivasarao M, Fisch MR, Kumar S. X-ray and Raman scattering study of orientational order in nematic and heliconical nematic liquid crystals. Phys Rev E 2016; 94:060701. [PMID: 28085478 DOI: 10.1103/physreve.94.060701] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Indexed: 05/16/2023]
Abstract
The temperature dependence of the orientational order parameters 〈P_{2}(cosβ)〉 and 〈P_{4}(cosβ)〉 in the nematic (N) and twist-bend nematic (N_{tb}) phases of the liquid crystal dimer CB7CB have been measured using x-ray and polarized Raman scattering. The 〈P_{2}(cosβ)〉 obtained from both techniques are the same, while 〈P_{4}(cosβ)〉, determined by Raman scattering is, as expected, systematically larger than its x-ray value. Both order parameters increase in the N phase with decreasing temperature, drop across the N-N_{tb} transition, and continue to decrease. In the N_{tb} phase, the x-ray value of 〈P_{4}(cosβ)〉 eventually becomes negative, providing a direct and independent confirmation of a conical molecular orientational distribution. The heliconical tilt angle α, determined from orientational distribution functions in the N_{tb} phase, increases to ∼24^{∘} at ∼15 K below the transition. In the N_{tb} phase, α(T)∝(T^{*}-T)^{λ}, with λ=0.19±0.03. The transition supercools by 1.7 K, consistent with its weakly first-order nature. The value of λ is close to 0.25 indicating close proximity to a tricritical point.
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Affiliation(s)
- Gautam Singh
- Department of Physics, Kent State University, Kent, Ohio 44242, USA
- Department of Applied Physics, Amity Institute of Applied Sciences, Amity University, Noida, UP 201313, India
| | - Jinxin Fu
- School of Materials Science and Engineering, School of Chemistry and Biochemistry, and Center for Advanced Research on Optical Microscopy, Georgia Institute of Technology, Atlanta, Georgia 30332-0295, USA
| | | | - Jang-Kun Song
- School of Electronic and Electrical Engineering, Sungkyunkwan University, Suwon, Republic of Korea
| | - M R Vengatesan
- School of Electronic and Electrical Engineering, Sungkyunkwan University, Suwon, Republic of Korea
| | - Mohan Srinivasarao
- School of Materials Science and Engineering, School of Chemistry and Biochemistry, and Center for Advanced Research on Optical Microscopy, Georgia Institute of Technology, Atlanta, Georgia 30332-0295, USA
| | - Michael R Fisch
- College of Applied Engineering Sustainability and Technology, Kent State University, Kent, Ohio 44242, USA
| | - Satyendra Kumar
- Department of Physics, Kent State University, Kent, Ohio 44242, USA
- Division of Research and Department of Physics, University at Albany, Albany, New York 12222, USA
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9
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Ranganathan S, Maji SK, Padinhateeri R. Defining a Physical Basis for Diversity in Protein Self-Assemblies Using a Minimal Model. J Am Chem Soc 2016; 138:13911-13922. [DOI: 10.1021/jacs.6b06433] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Srivastav Ranganathan
- Department of Biosciences
and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Samir K. Maji
- Department of Biosciences
and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Ranjith Padinhateeri
- Department of Biosciences
and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
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10
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Jenz F, Osipov MA, Jagiella S, Giesselmann F. Orientational distribution functions and order parameters in "de Vries"-type smectics: A simulation study. J Chem Phys 2016; 145:134901. [PMID: 27782446 DOI: 10.1063/1.4963660] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Simple smectic A liquid crystal phases with different types of prescribed orientational distribution functions have been simulated and compared in order to study the possibility to distinguish between the Maier-Saupe type and cone-like orientational distributions using the popular method of Davidson et al. [J. Phys. II 5, 113 (1995)]. This method has been used to extract the orientational distribution functions from simulated diffraction patterns, and the results have been compared with actual distribution functions which have been prescribed during simulations. It has been shown that it is indeed possible to distinguish between these two qualitatively different types of orientational distribution already from the shape of the 2D diffraction pattern. Moreover, typical experimental diffraction patterns for "de Vries"-type smectic liquid crystals appear to be close to the ones which have been simulated using the prescribed Maier-Saupe orientational distribution function.
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Affiliation(s)
- Frank Jenz
- Institute of Physical Chemistry, Pfaffenwaldring 55, University of Stuttgart, Stuttgart, Germany
| | - Mikhail A Osipov
- Department of Mathematics and Statistics, G1 1XH, University of Strathclyde, Glasgow, United Kingdom
| | - Stefan Jagiella
- Institute of Physical Chemistry, Pfaffenwaldring 55, University of Stuttgart, Stuttgart, Germany
| | - Frank Giesselmann
- Institute of Physical Chemistry, Pfaffenwaldring 55, University of Stuttgart, Stuttgart, Germany
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11
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Nozawa T, Takahashi KZ, Kameoka S, Narumi T, Yasuoka K. Application of isotropic periodic sum method for 4-pentyl-4′-cyanobiphenyl liquid crystal. MOLECULAR SIMULATION 2015. [DOI: 10.1080/08927022.2014.998210] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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12
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Sereda V, Lednev IK. Polarized Raman Spectroscopy of Aligned Insulin Fibrils. JOURNAL OF RAMAN SPECTROSCOPY : JRS 2014; 45:665-671. [PMID: 25316956 PMCID: PMC4194063 DOI: 10.1002/jrs.4523] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Amyloid fibrils are associated with many neurodegenerative diseases. The application of conventional techniques of structural biology, X-ray crystallography and solution NMR, for fibril characterization is limited because of the non-crystalline and insoluble nature of the fibrils. Here, polarized Raman spectroscopy was used to determine the orientation of selected chemical groups in aligned insulin fibrils, specifically of peptide carbonyls. The methodology is solely based on the measurement of the change in Raman scattered intensity as a function of the angle between the incident laser polarization and the aligned fibrils. The order parameters 〈 P2 〉 and 〈 P4 〉 of the orientation distribution function were obtained, and the most probable distribution of C=O group orientation was calculated. The results indicate that the peptides' carbonyl groups are oriented at an angle of 13±5° from the fibril axis, which is in consistent with previously reported qualitative descriptions of an almost parallel orientation of the C=O groups relative to the main fibril axis.
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Affiliation(s)
- Valentin Sereda
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Avenue, Albany, NY 12222, USA
| | - Igor K. Lednev
- Department of Chemistry, University at Albany, SUNY, 1400 Washington Avenue, Albany, NY 12222, USA
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13
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Roscioni OM, Muccioli L, Della Valle RG, Pizzirusso A, Ricci M, Zannoni C. Predicting the anchoring of liquid crystals at a solid surface: 5-cyanobiphenyl on cristobalite and glassy silica surfaces of increasing roughness. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:8950-8. [PMID: 23597166 DOI: 10.1021/la400857s] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
We employ atomistic molecular dynamics simulations to predict the alignment and anchoring strength of a typical nematic liquid crystal, 4-n-pentyl-4'-cyano biphenyl (5CB), on different forms of silica. In particular, we study a thin (~20 nm) film of 5CB supported on surfaces of crystalline (cristobalite) and amorphous silica of different roughness. We find that the orientational order at the surface and the anchoring strength depend on the morphology of the silica surface and its roughness. Cristobalite yields a uniform planar orientation and increases the order at the surface with respect to the bulk whereas amorphous glass has a disordering effect. Despite the low order at the amorphous surfaces, a planar orientation is established with a persistence length into the film higher than the one obtained for cristobalite.
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Affiliation(s)
- Otello Maria Roscioni
- Diartimento di Chimica Industriale Toso Montanari and INSTM, Università di Bologna, Bologna, Italy
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14
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Palermo MF, Pizzirusso A, Muccioli L, Zannoni C. An atomistic description of the nematic and smectic phases of 4-n-octyl-4′ cyanobiphenyl (8CB). J Chem Phys 2013; 138:204901. [DOI: 10.1063/1.4804270] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
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15
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Sanchez-Castillo A, Osipov MA, Jagiella S, Nguyen ZH, Kašpar M, Hamplovă V, Maclennan J, Giesselmann F. Orientational order parameters of a de Vries-type ferroelectric liquid crystal obtained by polarized Raman spectroscopy and x-ray diffraction. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:061703. [PMID: 23005110 DOI: 10.1103/physreve.85.061703] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Revised: 03/29/2012] [Indexed: 06/01/2023]
Abstract
The orientational order parameters (P{2}) and (P{4}) of the ferroelectric, de Vries-type liquid crystal 9HL have been determined in the SmA and SmC phases by means of polarized Raman spectroscopy, and in the SmA phase using x-ray diffraction. Quantum density functional theory predicts Raman spectra for 9HL that are in good agreement with the observations and indicates that the strong Raman band probed in the experiment corresponds to the uniaxial, coupled vibration of the three phenyl rings along the molecular long axis. The magnitudes of the orientational order parameters obtained in the Raman and x-ray experiments differ dramatically from each other, a discrepancy that is resolved by considering that the two techniques probe the orientational distributions of different molecular axes. We have developed a systematic procedure in which we calculate the angle between these axes and rescale the orientational order parameters obtained from x-ray scattering with results that are then in good agreement with the Raman data. At least in the case of 9HL, the results obtained by both techniques support a "sugar loaf" orientational distribution in the SmA phase with no qualitative difference to conventional smectics A. The role of individual molecular fragments in promoting de Vries-type behavior is considered.
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Affiliation(s)
- A Sanchez-Castillo
- Institut of Physical Chemistry, University of Stuttgart, Stuttgart, Germany
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16
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Yankova TS, Bobrovsky AY, Vorobiev AK. Order Parameters ⟨P2⟩, ⟨P4⟩, and ⟨P6⟩ of Aligned Nematic Liquid-Crystalline Polymer As Determined by Numerical Simulation of Electron Paramagnetic Resonance Spectra. J Phys Chem B 2012; 116:6010-6. [DOI: 10.1021/jp301170b] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- T. S. Yankova
- Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Leninskiye gory, 1/3,
Russia
| | - A. Yu. Bobrovsky
- Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Leninskiye gory, 1/3,
Russia
| | - A. Kh. Vorobiev
- Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Leninskiye gory, 1/3,
Russia
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Segnorile HH, Zamar RC. Quantum decoherence and quasi-equilibrium in open quantum systems with few degrees of freedom: application to 1H NMR of nematic liquid crystals. J Chem Phys 2011; 135:244509. [PMID: 22225171 DOI: 10.1063/1.3668559] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Explanation of decoherence and quasi-equilibrium in systems with few degrees of freedom demands a deep theoretical analysis that considers the observed system as an open quantum system. In this work, we study the problem of decoherence of an observed system of quantum interacting particles, coupled to a quantum lattice. Our strategy is based on treating the environment and the system-environment Hamiltonians fully quantum mechanically, which yields a representation of the time evolution operator useful for disentangling the different time scales underlying in the observed system dynamics. To describe the possible different stages of the dynamics of the observed system, we introduce quantum mechanical definitions of essentially isolated, essentially adiabatic, and thermal-contact system-environment interactions. This general approach is then applied to the study of decoherence and quasi-equilibrium in proton nuclear magnetic resonance ((1)H NMR) of nematic liquid crystals. A summary of the original results of this work is as follows. We calculate the decoherence function and apply it to describe the evolution of a coherent spin state, induced by the coupling with the molecular environment, in absence of spin-lattice relaxation. By assuming quantum energy conserving or non-demolition interactions, we identify an intermediate time scale, between those controlled by self-interactions and thermalization, where coherence decays irreversibly. This treatment is also adequate for explaining the buildup of quasi-equilibrium of the proton spin system, via the process we called eigen-selectivity. By analyzing a hypothetical time reversal experiment, we identify two sources of coherence loss which are of a very different nature and give rise to distinct time scales of the spin dynamics: (a) reversible or adiabatic quantum decoherence and (b) irreversible or essentially adiabatic quantum decoherence. Local irreversibility arises as a consequence of the uncertainty introduced by the coupling with an infinite quantum environment. The reversible part can be represented by a semiclassical model, similar to standard line-shape adiabatic models. By exploiting the separation existing between the time scales of the spin coherences and the irreversible decoherence, we present a novel technique to obtain the orientational molecular distribution function for a nematic liquid crystal. The procedure is based on the comparison of the observed coherence time evolution and numerical calculation under the adiabatic quantum decoherence approach. As an example, it is used the experimental free induction decay from a nematic PAA(d6) sample to extract such an orientational distribution. This is the first theoretical description of the experimental liquid crystal NMR signal in the time domain. On the contrary, the irreversible decoherence is intrinsically full-quantum mechanical, as it is governed by the commutation properties of the environment and the spin-lattice Hamiltonians. Consistently, it depends on the molecular correlation in a decisive way, since it vanishes under a mean-field model for the molecular dynamics. The results of this work can contribute to the understanding of the open question of the applicability of the spin-temperature concept in spin systems with few degrees of freedom.
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Affiliation(s)
- Héctor H Segnorile
- Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Córdoba, Argentina.
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Castriota M, Fasanella A, Cazzanelli E, De Sio L, Caputo R, Umeton C. In situ polarized micro-Raman investigation of periodic structures realized in liquid-crystalline composite materials. OPTICS EXPRESS 2011; 19:10494-10500. [PMID: 21643304 DOI: 10.1364/oe.19.010494] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In situ polarized micro-Raman Spectroscopy has been utilized to determine the liquid crystal configuration inside a periodic liquid crystalline composite structure made of polymer slices alternated to films of liquid crystal. Liquid crystal, Norland Optical Adhesive (NOA-61) monomer and its polymerized form have been investigated separately. The main Raman features, used as markers for the molecular orientation estimation, have been identified. In situ polarized Raman spectra indicate that the orientation of the liquid crystal director inside the structure is perpendicular to its polymeric slices. Results show the usefulness of in situ polarized micro-Raman spectroscopy to investigate liquid crystalline composite structures.
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Affiliation(s)
- Marco Castriota
- Liquid Crystal Laboratory, IPCF-CNR, Center of Excellence CEMIF.CAL and Department of Physics, University of Calabria, 87036 Arcavacata di Rende, CS, Italy.
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