Local gratings due to angular hole burning in a photorefractive polymer

Smith, Mark A.; Mitchell, Geoffrey R.; O'Leary, S.V.

doi:10.1088/1464-4258/4/4/318

Cited by 9 publications

(9 citation statements)

References 11 publications

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“… − Curve-fitting of the photoorientation kinetics indicates that for both complexes at all F A the time constant of the fast process is on the order of 15–30 s, while the slow process is more than an order of magnitude slower. The fast orientation process is generally ascribed to angular hole burning (AHB) of the trans isomers, and the slow process is associated with their angular redistribution (AR). , AHB is due to the rapid depletion of trans isomers with initial orientation along the laser polarization direction when isomerized to the cis form, − while AR, sometimes called orientational redistribution, involves progressive reorientation of the long axis of the chromophores perpendicular to the laser polarization direction during repeated trans – cis – trans cycles. − , AR is made possible by photoinduced rotational diffusion (RD), − which is strongly influenced by the lateral azo–azo interactions as well as internal molecular motions of the chromophore, such as bond torsion, rotation, and bending. , In the relaxation process, the fast and slow processes can be associated with the rapid thermal isomerization of the cis isomers back to trans conformation and to the much slower thermal RD of the oriented trans isomers toward the isotropic state, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…57,58 AHB is due to the rapid depletion of trans isomers with initial orientation along the laser polarization direction when isomerized to the cis form, [60][61][62] while AR, sometimes called orientational redistribution, 63 involves progressive reorientation of the long axis of the chromophores perpendicular to the laser polarization direction during repeated trans-cis-trans cycles. [60][61][62]64 AR is made possible by photoinduced rotational diffusion (RD), [65][66][67] which is strongly influenced by the lateral azo-azo interactions 65 as well as internal molecular motions of the chromophore, 68 such as bond torsion, rotation and bending. 69,70 In the relaxation process, the fast and slow processes can be associated with the rapid thermal isomerization of the cis isomers back to trans conformation and to the much slower thermal RD of the oriented trans isomers toward the isotropic state, respectively.…”

Section: Quantification Of the Extent Of Complexationmentioning

confidence: 99%

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Molecular-Level Study of Photoorientation in Hydrogen-Bonded Azopolymer Complexes

et al. 2018

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To optimize azobenzene-containing materials for applications such as rewritable waveguides and holographic data storage, it is imperative to understand the effect of the azobenzene structure on the photoresponse of the material. Supramolecular materials, in which a complexed photoactive azobenzene controls the motion or other properties of a passive polymer, are uniquely convenient for studying the impact of specific chemical modifications. Here, we use polarization modulation infrared structural absorbance spectroscopy (PM-IRSAS) to hydrogen-bonded supramolecular azobenzene complexes using poly(4-vinylpyridine) (P4VP) as a model polymer. We show that changing the tail group from hydrogen (AH) to cyano (ACN) induces greater angular redistribution of the chromophores and, remarkably, provokes P4VP pyridine ring orientation. Increasing the degree of complexation decreases the saturated orientation of both AH and ACN, whereas for P4VP/ACN it increases the pyridine orientation as well as the orientation stability of both components. These results explain the contrasting photoinduced birefringence behavior previously observed for these complexes and identify azo-azo intermolecular interactions as the main reason. To our knowledge, this is the first molecular-level spectroscopic analysis of the contrasting contributions of azobenzenes to the photo-orientation of supramolecular azopolymer complexes and the first report of the large impact of small molecular changes on the capacity of azo dyes to transfer light-induced orientation to a photopassive polymer. 29 bonds. In many cases, the passive polymer host employed is poly(4-vinylpyridine) (P4VP). [16][17][18][19][20][21][23][24][25][26][27][28][29] Various studies have revealed that the chemical structure and the content of the supramolecularly attached azo have significant impact on the measured PIB [23][24][25]30 and on SRG formation efficiency. [20][21][22] For example, the saturated PIB per azobenzene unit of hydrogen-bonded P4VP-azo complexes, where the azos used differ only by the nature of its tail group (Scheme 1), increases by more than a factor of 2 when increasing azo content for the cyano-tailed azo (CN-tailed or ACN), whereas it decreases by up to a factor of 2 for the hydrogen-tailed azo (H-tailed or AH). 25

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Section: Resultsmentioning

confidence: 99%

Section: Quantification Of the Extent Of Complexationmentioning

confidence: 99%

Molecular-Level Study of Photoorientation in Hydrogen-Bonded Azopolymer Complexes

et al. 2018

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“…Changes in the diffraction efficiency and coef ficients of nonlinear refraction and cubic susceptibility have been observed in systems based on poly(vinyl car bazole), polyimide (PI), and other polymer matrices, as well as in liquid crystalline materials sensitized by nanoobjects [1][2][3][4][5]. The investigations performed by the author with coworkers have also contributed to research in this field of materials science [6][7][8][9][10][11].…”

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confidence: 99%

The effect of the charge transfer pathway during intermolecular complex formation on nonlinear optical and photoconducting properties of nanocomposites

Каманина

2012

Tech. Phys. Lett.

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In the past decade, the influence of nanostructure and complex formation in conjugated organic systems sensitized by new effective nanoobjects-such as fullerenes, carbon nanotubes (CNTs), and quantum dots (QDs)-on nonlinear optical and photoconduct ing properties of these materials has been actively dis cussed. Changes in the diffraction efficiency and coef ficients of nonlinear refraction and cubic susceptibility have been observed in systems based on poly(vinyl car bazole), polyimide (PI), and other polymer matrices, as well as in liquid crystalline materials sensitized by nanoobjects [1][2][3][4][5]. The investigations performed by the author with coworkers have also contributed to research in this field of materials science [6][7][8][9][10][11].There are some discrepancies in the published data on photorefraction, which are related to difficulties encountered in attempts to directly separate mecha nisms of the diffusion and drift of charge carriers and strictly determine the pathlengths of the charge trans fer in systems with donor-acceptor interaction under conditions in which intermolecular complex forma tion is dominant over intramolecular processes. These discrepancies hindered an adequate explanation of differences in nonlinear optical parameters observed at various spatial frequencies for the same conjugated matrix and the same concentration of a sensitizer.This Letter presents the results of an analysis and systematization of data on photorefraction in applica tion to a PI-CNT model system. On this basis, we will consider the possible influence of the arrangement of a sensitizing nanoobject and the charge transfer path way during intermolecular complex formation on nonlinear optical properties and photoconductivity characteristics of nanocomposites.Experimental investigations have been performed on thin (1-3 μm thick) PI films containing tripheny lamine and diimide fragments that play the roles of intramolecular donor and acceptor, respectively. The PI matrix was doped by various dispersed sensitizing additives based on nanoobjects such as fullerenes, QDs, shungites, CNTs, and mixtures of CNTs with nanofibers (CNT/NF). Nanosensitizing additives of the latter type are advantageous in being inexpensive as they are available from domestic manufacturers and ensuring good reproducibility of experimental data (comparable in this respect to the results obtained with pure fullerenes and single walled nanotubes). The concentrations c of fullerenes, QDs, shungites, CNTs (or CNT/NF mixtures) amounted to 0.03-0.003, 0.1-0.2, 0.05-0.1, and 0.1 wt %, respectively (relative to the dry matrix substance). Thin films were prepared using tetrachloroethane as a solvent.The properties of the obtained nanocomposites were studied using pulsed second harmonic radiation of a neodymium laser operating at a wavelength of 532 nm and pulse durations within τ ~ 10-20 ns. Gratings were recorded using variable incident energy density (W in ) at various spatial frequencies Λ (90, 100, 150, and 170 mm -1 ). Experiments were performed u...

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“…The changes in the diffraction efficiency and the coefficients of the nonlinear refraction and the cubic susceptibility have been observed in the systems based on the poly(vinyl carbazole), polyimide (PI), pyridines, polyaniline, and other polymer matrices as well as in the liquid–crystalline materials sensitized by the abovementioned nanoobjects [ 28 , 29 , 30 ]. The investigations performed by the author with coworkers have also contributed to the research in this field of materials science.…”

Section: Introductionmentioning

confidence: 99%

Advances in Material Nanosensitization: Refractive Property Changes as the Main Parameter to Indicate Organic Material Physical–Chemical Feature Improvements

Каманина

2022

Materials

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In the current paper, the results of the sensitization process’ influence on the refractive organic materials’ features are shown. The correlation between the refractive properties and the intermolecular charge transfer effect of doped organic thin films are shown via estimation of the laser-induced change in the refractive index. The refractive parameter is shown for a model organics matrix based on a polyimide doped with fullerenes, carbon nanotubes, reduced graphene oxides, etc. A second harmonic of the Nd-laser was used to record the holographic gratings in the Raman–Nath diffraction conditions at different spatial frequencies. The laser-induced refractive index change was considered to be an indicator in order to estimate the basic organic materials’ physical–chemical characteristics. Additional data are presented for the liquid crystal cells doped with nanoparticles. The correlation between the content of the nanoobjects in the organics’ bodies and the contact angle at the thin film surfaces is shown. Some propose to use this effect for general optoelectronics, for the optical limiting process, and for display application.

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Local gratings due to angular hole burning in a photorefractive polymer

Cited by 9 publications

References 11 publications

Molecular-Level Study of Photoorientation in Hydrogen-Bonded Azopolymer Complexes

Molecular-Level Study of Photoorientation in Hydrogen-Bonded Azopolymer Complexes

The effect of the charge transfer pathway during intermolecular complex formation on nonlinear optical and photoconducting properties of nanocomposites

Advances in Material Nanosensitization: Refractive Property Changes as the Main Parameter to Indicate Organic Material Physical–Chemical Feature Improvements

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