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Open AccessArticle

Modeling of Stripe Patterns in Photosensitive Azopolymers

Leibniz-Institut für Polymerforschung, Hohe Straße 6, 01069 Dresden, Germany
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Polymers 2020, 12(4), 735; https://doi.org/10.3390/polym12040735
Received: 24 February 2020 / Revised: 20 March 2020 / Accepted: 21 March 2020 / Published: 26 March 2020
(This article belongs to the Special Issue Theory of Polymers at Interfaces)
Placed at interfaces, azobenzene-containing materials show extraordinary phenomena when subjected to external light sources. Here we model the surface changes induced by one-dimensional Gaussian light fields in thin azopolymer films. Such fields can be produced in a quickly moving film irradiated with a strongly focused laser beam or illuminating the sample through a cylindrical lens. To explain the appearance of stripe patterns, we first calculate the unbalanced mechanical stresses induced by one-dimensional Gaussian fields in the interior of the film. In accordance with our orientation approach, the light-induced stress originates from the reorientation of azobenzenes that causes orientation of rigid backbone segments along the light polarization. The resulting volume forces have different signs and amplitude for light polarization directed perpendicular and parallel to the moving direction. Accordingly, the grooves are produced by the stretching forces and elongated protrusions by the compressive forces. Implementation into a viscoplastic model in a finite element software predicts a considerably weaker effect for the light polarized along the moving direction, in accordance with the experimental observations. The maximum value in the distribution of light-induced stresses becomes in this case very close to the yield stress which results in smaller surface deformations of the glassy azopolymer. View Full-Text
Keywords: azopolymers; surface patterning; viscoplastic modeling azopolymers; surface patterning; viscoplastic modeling
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MDPI and ACS Style

Yadav, B.; Domurath, J.; Saphiannikova, M. Modeling of Stripe Patterns in Photosensitive Azopolymers. Polymers 2020, 12, 735.

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