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de Souza RF, Zannoni C. Rotational diffusion of shape switching particles in nematic liquid crystals. Phys Rev E 2017; 94:062702. [PMID: 28085296 DOI: 10.1103/physreve.94.062702] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Indexed: 11/07/2022]
Abstract
The theory of rotational diffusion of particles of various symmetry embedded in a liquid crystal host, essential to interpret a variety of spectroscopic observables, has been available for some time, but only for the case of rigid molecules. Here we generalize the treatment and present a theory to describe the rotational diffusion of shape-changing particles dispersed in nematic liquid crystals. The interaction of the particles with the environment is modeled by an effective field potential, while the particles are allowed to assume an arbitrary discrete number of shapes. The transition between shapes is modeled by a Markovian process which is combined with rotational diffusion. Our model is applied to the simple case of a particle that can exchange between three shapes: a rod, a disk, and a sphere. We consider in detail the effect of shape transitions in some selected correlation functions which are relevant for experiments.
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Affiliation(s)
- R F de Souza
- Dipartimento di Chimica Industriale "Toso Montanari" and INSTM, Università di Bologna, Viale del Risorgimento 4, 40136 Bologna, Italy.,CAPES Foundation, Ministry of Education of Brazil, Brasília, DF 70040-020, Brazil
| | - C Zannoni
- Dipartimento di Chimica Industriale "Toso Montanari" and INSTM, Università di Bologna, Viale del Risorgimento 4, 40136 Bologna, Italy
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Satoh K. Thermodynamic scaling of dynamic properties of liquid crystals: verifying the scaling parameters using a molecular model. J Chem Phys 2013; 139:084901. [PMID: 24007031 DOI: 10.1063/1.4818418] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The thermodynamic scaling of molecular dynamic properties of rotation and thermodynamic parameters in a nematic phase was investigated by a molecular dynamic simulation using the Gay-Berne potential. A master curve for the relaxation time of flip-flop motion was obtained using thermodynamic scaling, and the dynamic property could be solely expressed as a function of TV(γτ) , where T and V are the temperature and volume, respectively. The scaling parameter γτ was in excellent agreement with the thermodynamic parameter Γ, which is the logarithm of the slope of a line plotted for the temperature and volume at constant P2. This line was fairly linear, and as good as the line for p-azoxyanisole or using the highly ordered small cluster model. The equivalence relation between Γ and γ(τ) was compared with results obtained from the highly ordered small cluster model. The possibility of adapting the molecular model for the thermodynamic scaling of other dynamic rotational properties was also explored. The rotational diffusion constant and rotational viscosity coefficients, which were calculated using established theoretical and experimental expressions, were rescaled onto master curves with the same scaling parameters. The simulation illustrates the universal nature of the equivalence relation for liquid crystals.
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Affiliation(s)
- Katsuhiko Satoh
- Department of Chemistry, College of General Education, Osaka Sangyo University, 3-1-1 Nakagaito, Daito, Osaka 574-8530, Japan
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Satoh K. Characteristic behavior of short-term dynamics in reorientation for Gay-Berne particles near the nematic-isotropic phase transition temperature. J Chem Phys 2006; 125:204902. [PMID: 17144735 DOI: 10.1063/1.2393238] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
A specific transition behavior was found in the tumbling motion near the nematic-isotropic phase boundary using molecular dynamics simulations of the Gay-Berne mesogenic model under isobaric conditions at a reduced pressure P* of 2.0. The relaxation time for the motion obtained from the second-rank orientational time correlation function and the rotational diffusion coefficient showed a clear jump at the nematic-isotropic phase transition temperature. Regardless of the temperature dependence of the relaxation time, the change in the rotational diffusion coefficient evaluated from the orientational order parameters and the relaxation time agreed qualitatively with that of real mesogens. The rotational viscosity coefficients gamma(1) and gamma(2) were obtained from the simulation data for the relaxation time for the short-term dynamics and for the rotational diffusion coefficients. gamma(1) was proportional to <P2>(2), where <P2> is the second-rank orientational parameter. Furthermore, the rotational behavior of the model was compared with that of the Debye approximation in the isotropic phase.
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Affiliation(s)
- Katsuhiko Satoh
- College of General Education, Osaka Sangyo University, 3-1-1 Nakagaito, Daito, Osaka 574-8530, Japan.
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Arcioni A, van Zandvoort MAMJ, Bartolini P, Torre R, Tarroni R, Righini R, Zannoni C. Effective Shape and Dynamics of Chlorophyll a in a Nematic Liquid Crystal. J Phys Chem B 1998. [DOI: 10.1021/jp9726504] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alberto Arcioni
- Dipartimento di Chimica Fisica e Inorganica, Università degli Studi di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy, LENS (European Laboratory for Non-linear Spectroscopy), Università, Largo E. Fermi 2, I-50125 Firenze, Italy, and Dipartimento di Chimica, Università, Via G. Capponi 9, I-50121 Firenze, Italy
| | - Marc A. M. J. van Zandvoort
- Dipartimento di Chimica Fisica e Inorganica, Università degli Studi di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy, LENS (European Laboratory for Non-linear Spectroscopy), Università, Largo E. Fermi 2, I-50125 Firenze, Italy, and Dipartimento di Chimica, Università, Via G. Capponi 9, I-50121 Firenze, Italy
| | - Paolo Bartolini
- Dipartimento di Chimica Fisica e Inorganica, Università degli Studi di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy, LENS (European Laboratory for Non-linear Spectroscopy), Università, Largo E. Fermi 2, I-50125 Firenze, Italy, and Dipartimento di Chimica, Università, Via G. Capponi 9, I-50121 Firenze, Italy
| | - Renato Torre
- Dipartimento di Chimica Fisica e Inorganica, Università degli Studi di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy, LENS (European Laboratory for Non-linear Spectroscopy), Università, Largo E. Fermi 2, I-50125 Firenze, Italy, and Dipartimento di Chimica, Università, Via G. Capponi 9, I-50121 Firenze, Italy
| | - Riccardo Tarroni
- Dipartimento di Chimica Fisica e Inorganica, Università degli Studi di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy, LENS (European Laboratory for Non-linear Spectroscopy), Università, Largo E. Fermi 2, I-50125 Firenze, Italy, and Dipartimento di Chimica, Università, Via G. Capponi 9, I-50121 Firenze, Italy
| | - Roberto Righini
- Dipartimento di Chimica Fisica e Inorganica, Università degli Studi di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy, LENS (European Laboratory for Non-linear Spectroscopy), Università, Largo E. Fermi 2, I-50125 Firenze, Italy, and Dipartimento di Chimica, Università, Via G. Capponi 9, I-50121 Firenze, Italy
| | - Claudio Zannoni
- Dipartimento di Chimica Fisica e Inorganica, Università degli Studi di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy, LENS (European Laboratory for Non-linear Spectroscopy), Università, Largo E. Fermi 2, I-50125 Firenze, Italy, and Dipartimento di Chimica, Università, Via G. Capponi 9, I-50121 Firenze, Italy
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Dong RY, Shen X. Dynamics of a Liquid Crystal by Deuterium NMR: The Analysis of Director Fluctuations and Reorientation of Molecules. J Phys Chem A 1997. [DOI: 10.1021/jp970798h] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ronald Y. Dong
- Department of Physics and Astronomy, Brandon University, Brandon, Manitoba R7A 6A9, Canada, and Physics Department, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Xiaodong Shen
- Physics Department, Univerisity of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
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