Photoinduced reorientation in liquid‐crystalline polymers below the glass transition temperature studied by time‐dependent infrared spectroscopy

Wiesner, Ulrich; Reynolds, Nicholas; Boeffel, Christine; Spieß, Hans Wolfgang

doi:10.1002/marc.1991.030120801

Cited by 106 publications

(77 citation statements)

References 11 publications

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“…There are a number of reports on the photoinduced out-of-plane reorientation of azobenzenes. [37][38][39][40][41] Moreover, spectroscopic evidence reported to date is consistent with the out-of-plane orientation of azobenzene molecules, reorientation of azobenzene chromophores toward the direction of propagation of the excitation light. [42,43] In order to evaluate the photoinduced in-plane and out-of-plane orientations of azobenzene chromophores, angular resolved absorption spectra of photoirradiated films were usually measured with various incident angles of probe light, which are defined as the angles between the propagation direction of light and the surface normal.…”

Section: Photo-induced Stop-band Tunability In a Pdo3 Infiltrated Andsupporting

confidence: 74%

Photoinduced Tuning of Optical Stop Bands in Azopolymer Based Inverse Opal Photonic Crystals

Hong

Park

Chun

et al. 2007

Adv Funct Materials

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Photo‐tunable photonic crystals were prepared from three dimensional (3D) colloidal crystal templates using a photoresponsive azopolymer. For the preparation of azopolymer infiltrated photonic crystals, silica colloidal crystals were fabricated by gravity sedimentation, a self‐assembly technique. The interstitial voids between colloidal particles were filled with azopolymer and azopolymer inverse opals were produced by treatment with aqueous hydrofluoric acid. These photonic crystals exhibited stop bands in their transmission spectra measured in the normal incidence to the (111) plane of face centered cubic (fcc). The photonic bandgap of the azopolymer infiltrated opal and inverse opal could be controlled by the refractive index change due to the photoinduced orientation of azobenzene chromophores. When the azopolymer photonic crystals were irradiated with linearly polarized light, their bandgap positions were shifted to shorter wavelength regions with increasing irradiation time. This behavior experimentally produced a photoinduced orientation of the azobenzene groups in parallel with the incidence of the excitation light. Through such an out‐of‐plane orientation of azo chromophores, parallel to the [111] fcc crystallographic axis, the effective refractive index of the photonic crystal medium was decreased. Therefore, a blue‐shift in bandgap positions was consequently induced with 20–40 nm tuning ranges. The out‐of‐plane orientation was confirmed by angular resolved absorption spectral measurements.

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Section: Photo-induced Stop-band Tunability In a Pdo3 Infiltrated Andsupporting

confidence: 74%

Photoinduced Tuning of Optical Stop Bands in Azopolymer Based Inverse Opal Photonic Crystals

Hong

Park

Chun

et al. 2007

Adv Funct Materials

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“…[121] Dieser Effekt tritt ebenfalls bei einer reinen trans-cis-Isomerisierung in Gegenwart anderer mesogener Gruppen auf. [119,[122][123][124] Dafür müssen die Substituenten an den mesogenen Einheiten zur Bildung sterischer oder dipolarer Wechselwirkungen auf die Azobenzolseitenketten abgestimmt werden. Untersuchungen haben gezeigt, dass dieser "Nachbargruppeneffekt" nur für Gruppen derselben Polymerhauptkette auftritt.…”

Section: Photochrome Und Andereunclassified

Von der Fläche ins Volumen – Materialkonzepte für optisch‐holographische Datenspeicher der Zukunft

et al. 2011

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Die optische Datenspeicherung hat seit Ihrer Markteinführung 1982 das tägliche Leben geprägt. Compact Disk (CD), Digital Versatile Disk (DVD) und Blu‐ray Disk (BD) sind universelle Datenträgerformate mit den Vorteilen des kontaktfreien und damit abnutzungslosen Lesens und Schreibens der digitalen Daten. Sie ermöglichen einen schnellen Datenzugriff, hohe Transferraten und eine stromfreie Datenspeicherung bei sehr günstigen gesamten Archivierungskosten. Der stete Wunsch nach der Erhöhung der Datenspeicherkapazitäten und ‐transferraten treibt die Entwicklung an. Für optische Datenspeicher ist die Nutzung holographischer Prinzipien ein eleganter Weg, diese Parameter weiter zu erhöhen, da hier im Inneren (also im Volumen) des Speichermaterials Daten abgelegt werden und zudem optisch parallel verarbeitet werden können. Dieser Aufsatz beschreibt die grundlegenden Materialanforderungen für holographische Speicher und vergleicht generelle Materialkonzepte. Ein Überblick über aktuelle Demonstrationen von Lese‐Schreib‐Geräten zeigt auf, wie weit die holographische Datenspeicherung schon entwickelt wurde.

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“…It was found that when the power was lower than 9.55 mW Á cm À2 , the transmittance of the probe light would be not obvious and the alignment could not be observed. Furthermore, most experiments of photo-induced alignment are executed at a temperature of about 30 8C [14] to 40 8C [15] below T g and no observation of photo-induced alignment behavior at a lower temperature is reported. These experiment phenomena are hard to explain, since the photochemical reaction is not found to have activation energy.…”

Section: à2mentioning

confidence: 99%

Dynamic Temperature Distribution in Photo‐induced Alignment of Azobenzene Liquid Crystalline Polymer

Zhao

Zhang

Yong

et al. 2003

Macro Theory & Simulations

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A theoretical model has been established to describe the dynamic temperature distribution during the alignment of an azobenzene liquid crystalline polymer irradiated by a linearly polarized laser beam. The dynamic heat diffusion equations are used, and the relationship between heat source item and time is introduced, based on experimental results. With the model, the contours of the temperature distribution at different time have been worked out. It can be found from the theoretical model that there is a maximum temperature rise during the photo‐induced alignment, which is coincident with the analysis of experimental observations. The existence of a minimum laser power and an offset photo‐alignment temperature Toff required to carry on photo‐induce alignment are explained based on the theoretical model.Temperature distribution after two minutes.imageTemperature distribution after two minutes.

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Photoinduced reorientation in liquid‐crystalline polymers below the glass transition temperature studied by time‐dependent infrared spectroscopy

Cited by 106 publications

References 11 publications

Photoinduced Tuning of Optical Stop Bands in Azopolymer Based Inverse Opal Photonic Crystals

Photoinduced Tuning of Optical Stop Bands in Azopolymer Based Inverse Opal Photonic Crystals

Von der Fläche ins Volumen – Materialkonzepte für optisch‐holographische Datenspeicher der Zukunft

Dynamic Temperature Distribution in Photo‐induced Alignment of Azobenzene Liquid Crystalline Polymer

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