Kinetics of photoinduced anisotropy in azopolymers: models and mechanisms

Kiselev, Alexei D.

doi:10.1088/0953-8984/14/49/301

Cited by 19 publications

(40 citation statements)

References 32 publications

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“…It gives the value of λ equal to (1 + 0.6 √ 30)/7. The results of numerical analysis reported in [31] shows that this heuristic procedure gives reasonably accurate approximation for correlators of the mean field distributions (26).…”

Section: Modelmentioning

confidence: 89%

“…[18,31]. This approach describes the kinetics of POA in terms of one-particle angular distribution functions and angular redistribution probabilities.…”

Section: Discussion and Conclu-sionsmentioning

confidence: 99%

“…(More details on the model and the underlying phenomenological approach can be found in Refs. [18,31]). …”

Section: Modelmentioning

confidence: 99%

“…In Sec. IV we describe the theoretical model formulated by using the phenomenological approach of [18,31]. We discuss the physical assumptions underlying the model and make brief comments on the derivation of the kinetic equations for the concentrations of isomers and the order parameter tensor.…”

Section: Introductionmentioning

confidence: 99%

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Photoinduced three-dimensional orientational order in side chain liquid crystalline azopolymers

et al. 2003

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We apply experimental technique based on the combination of methods dealing with principal refractive indices and absorption coefficients to study the photoinduced 3D orientational order in the films of liquid crystalline (LC) azopolymers. The technique is used to identify 3D orientational configurations of trans azobenzene chromophores and to characterize the degree of ordering in terms of order parameters. We study two types of LC azopolymers which form structures with preferred in-plane and out-of-plane alignment of azochromophores, correspondingly. Using irradiation with the polarized light of two different wavelengths we find that the kinetics of photoinduced anisotropy can be dominated by either photo-reorientation (angular redistribution of trans chromophores) or photoselection (angular selective trans-cis isomerization) mechanisms depending on the wavelength. At early stages of irradiation the films of both azopolymers are biaxial. This biaxiality disappears on reaching a state of photo-saturation. In the regime of photoselection the photo-saturated state of the film is optically isotropic. But, in the case of the photo-reorientation mechanism, anisotropy of this state is uniaxial with the optical axis dependent on the preferential alignment of azochromophores. We formulate the phenomenological model describing the kinetics of photoinduced anisotropy in terms of the isomer concentrations and the order parameter tensor. We present the numerical results for absorption coefficients that are found to be in good agreement with the experimental data. The model is also used to interpret the effect of changing the mechanism with the wavelength of the pumping light.

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Section: Modelmentioning

confidence: 89%

“…[18,31]. This approach describes the kinetics of POA in terms of one-particle angular distribution functions and angular redistribution probabilities.…”

Section: Discussion and Conclu-sionsmentioning

confidence: 99%

“…(More details on the model and the underlying phenomenological approach can be found in Refs. [18,31]). …”

Section: Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photoinduced three-dimensional orientational order in side chain liquid crystalline azopolymers

et al. 2003

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“…[18][19][20][21][22][23][24][25][26][27] Molecular interactions are treated within mean-field approximation, where microscopic details such as the different shapes of the isomers are neglected.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Monte Carlo simulations for birefringence relaxation of photo-switchable molecules on a surface

Tavarone

Stark

2016

The Journal of Chemical Physics

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Recent experiments have demonstrated that in a dense monolayer of photo-switchable dye methyl-red molecules the relaxation of an initial birefringence follows a power-law decay, typical for glass-like dynamics. The slow relaxation can efficiently be controlled and accelerated by illuminating the monolayer with circularly polarized light, which induces trans-cis isomerization cycles. To elucidate the microscopic mechanism, we develop a two-dimensional molecular model in which the trans and cis isomers are represented by straight and bent needles, respectively. As in the experimental system, the needles are allowed to rotate and to form overlaps but they cannot translate. The out-ofequilibrium rotational dynamics of the needles is generated using kinetic Monte Carlo simulations. We demonstrate that, in a regime of high density and low temperature, the power-law relaxation can be traced to the formation of spatio-temporal correlations in the rotational dynamics, i.e., dynamic heterogeneity. We also show that the nearly isotropic cis isomers can prevent dynamic heterogeneity from forming in the monolayer and that the relaxation then becomes exponential. C 2016 AIP Publishing LLC. [http://dx

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