Photoorientation in Lb Multilayers of Thermotropic Polymers

Stumpe, Joachim; Fischer, Thomas; Ziegler, A.; Geue, Thomas; Menzel, Henning

doi:10.1080/10587259708042001

Cited by 10 publications

(3 citation statements)

References 10 publications

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“…In the case of the film, prepared by pressing a dendrimer drop between quartz plates (Figure 2b), the absorption maximum of the π-π* transition is somewhat shifted to shorter wavelengths. As is shown for LC side chain azobenzene-containing polymers, [15][16][17][18][19] this behavior is caused by the aggregation of azobenzene chromophores because of π-π stacking. This headto-head aggregation is always promoted by the development of smectic order.…”

Section: Resultsmentioning

confidence: 97%

Photochemical and Photoorientational Behavior of Liquid Crystalline Carbosilane Dendrimer with Azobenzene Terminal Groups

et al. 2001

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The photochemical and photooptical properties of the first-generation LC dendrimer with terminal azobenzene groups which forms a SmA mesophase in a wide temperature range have been studied. A comparative analysis of its photochemical behavior in a dilute solution and a thin film was carried out. Under the action of UV irradiation, the E/Z photoisomerization of the azobenzene group takes place both in the solution and in the film. This process is found to be photochemically and thermally reversible. The kinetics of the thermal Z/E process is studied, and the activation energy of the process is calculated. The process of the photoinduced orientation of the terminal azobenzene groups in films of the dendrimer upon irradiation with linearly polarized UV light (365 nm) and with the green light of an Ar + laser (488 nm) was studied. Under irradiation with linearly polarized UV light, the E/Z isomerization takes place, but photoorientation is not observed. However, in the case of linearly polarized green light exposure (488 nm), a well pronounced linear dichroism is generated. The kinetics of the process was studied, and the photoinduced orientational order parameter was calculated.

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Section: Resultsmentioning

confidence: 97%

Photochemical and Photoorientational Behavior of Liquid Crystalline Carbosilane Dendrimer with Azobenzene Terminal Groups

et al. 2001

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“…Therefore, monodomain samples should be prepared first, to achieve an acceptable transparency required for optical applications, and the thicker the film, the more difficult is to obtain the large size non‐defect monodomain orientation. Of the most usage are the Langmuir‐Blodgett films consisting of several molecular layers,19,20 the 0.05–0.5 μm thick spin‐coated films,21–23 or 1–5 μm thick cast films 24,25. We should notice also that the monodomain samples of LC polymers possess ab initio a macroscopic birefringence which has to be overcome during the photorecording process, thus reducing photosensitivity of the film.…”

Section: Introductionmentioning

confidence: 99%

The Photoinduced Birefringence in Thick Films of Chiral Azodye Copolymers

Kozlovsky

Лазарев

2003

Macro Chemistry & Physics

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The photoinduced birefringence, Δnind, in 19–35 μm thick films has been studied for two series of chiral photochromic liquid crystalline side chain copolymers. The birefringence measured is induced by excitation of the n‐π* band only. The Δnind value induced in 10 min is linear upon concentration of dye moieties but achieves saturation with increase of illumination intensity. Evolution of the birefringence can be described by double exponent growth; the faster exponent is the same for both copolymer series and should relate to the photoselection process, while the slower one should relate mainly to photo‐orientation and differs strongly dependent on chemical structure of photochromic groups. The different behaviour of two copolymer series during the growth governed by the second exponent is interpreted in terms of the “frictional model”. Due to elevated thickness of the films, rather moderate Δnind values result in huge phase retardation up to 270° and more. The materials are promising therefore for holography applications.

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“…Quite a diOE erent situation is observed in the case of azobenzene-containing photosensi tive systems [ 1,2,[10][11][12][13][14][15][16][17][18][19][20][21][22][23] which have been studied in detail. It is well known, that 1382 A. Y. Bobrovsky et al…”

Section: Introductionmentioning

confidence: 99%