An infrared spectroscopic study of photo-induced reorientation in dye containing liquid-crystalline polymers

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

doi:10.1080/02678299208028986

Cited by 114 publications

(90 citation statements)

References 18 publications

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“…[10,15]. In addition, it was found that the photoinduced orientational structures can show biaxiality [8,10,16,17,18].…”

Section: Introductionmentioning

confidence: 99%

“…This, however, can be done in the regime of POA where the fraction of cis isomers is negligible (the photo-reorientation mechanism) by using the method proposed in Refs. [8,36]. The key point is that the sum of all the principal absorption coefficients,…”

Section: Absorption Methodsmentioning

confidence: 99%

“…The stable POA was observed later on in polymers containing chemically linked azochromophores (azopolymers) [4]. It turned out that stable anisotropy can be induced in both amorphous and liquid crystalline (LC) azopolymers [4,5,6,7,8,9,10]. The efficiency of POA in LC azopolymers is generally much higher than it is for amorphous homologues.…”

Section: Introductionmentioning

confidence: 99%

“…These methods have the indisputable advantage that the order parameters of various molecular groups can be estimated from the results of these measurements. Shortcomings of the known absorption methods [8,27] are the limited field of applications and the strong approximations.…”

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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“…[10,15]. In addition, it was found that the photoinduced orientational structures can show biaxiality [8,10,16,17,18].…”

Section: Introductionmentioning

confidence: 99%

Section: Absorption Methodsmentioning

confidence: 99%

Section: Introductionmentioning

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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“…10,11 These studies clearly indicate that cooperative motions are possible in amorphous polymers, even below T g , and that the polarity of the groups involved in the cooperative motions is an important factor. Similarly, the photoinduced orientation of azobenzene groups has been used to reorient non photochromic groups in liquid crystalline (LC) polymers [12][13][14][15] or to align LC molecules in Langmuir-Blodgett films. 16,17 The nature of the matrix in the doped polymer systems is also a factor that influences the angular reorientation of azobenzene derivatives.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Orientation of Azobenzene Chromophores in Amorphous Polymers As Studied by Real-Time Visible and FTIR Spectroscopies

et al. 1998

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ABSTRACT:In situ dynamical study of the photoinduced orientation of the DR1 azobenzene derivative in a doped PMMA matrix and in p(DR1A-co-MMA) copolymers was carried out using real-time visible and infrared spectroscopies. The different mechanisms occurring during the photoisomerization cycles were highlighted by following the time dependence of the normalized average absorbance (T 0), the normalized linear dichroism (T2) and the order parameter (P2) during the orientation (laser on) and the relaxation (laser off) periods. The thermal cis-trans back-relaxation and the angular redistribution were followed separately from the T0 and T2 relaxation curves, respectively. The orientation and relaxation curves were fitted by the Kohlrausch-Williams-Watts (KWW) function in order to compare the rate constant and the distribution width for various samples. On one hand, the chromophore-matrix interactions were investigated in doped systems by changing the tacticity of the PMMA matrix. On the other hand, the chromophore-chromophore interactions in functionalized polymers were studied by changing the concentration of azobenzene units in copolymer systems.

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Synthesis, characterization and liquid crystalline properties of polyacrylates and polymethacrylates containing aryl ester pendant unit

Sainath

Rao

Reddy

2000

J. Appl. Polym. Sci.

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Aryloxycarbonylphenyl acrylates and methacrylates were prepared by reacting 4-acryloyloxybenzoyl chloride and 4-methacryloyloxybenzoyl chloride with different phenols. They were homopolymerized using benzoyl peroxide as the initiator at 65°C in dimethylformamide. The polymers were characterized by IR and 1 H-NMR spectra and size exclusion chromatography. Differential scanning calorimetry and polarizing optical microscopy studies revealed that the phenyl esters of poly(4-acryloyloxybenzoic acid) and poly(4-methacryloyloxybenzoic acid) did not show any liquid crystalline properties, but, the para-aryl-substituted phenyl esters did exhibit mesophase properties in the temperature range of 98 -265°C depending on the nature of the aryl substituent. Polymethacrylates exhibit higher T g , and lower T m and T i than the polyacrylates having the same pendant mesogen. Thermogravimetric analyses have shown that the initial decomposition temperatures of the polymers are above 230°C.

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An infrared spectroscopic study of photo-induced reorientation in dye containing liquid-crystalline polymers

Cited by 114 publications

References 18 publications

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

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

Photoinduced Orientation of Azobenzene Chromophores in Amorphous Polymers As Studied by Real-Time Visible and FTIR Spectroscopies

Synthesis, characterization and liquid crystalline properties of polyacrylates and polymethacrylates containing aryl ester pendant unit

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