Molecular Orientations in Azopolymer Holographic Diffraction Gratings as Studied by Raman Confocal Microspectroscopy

Labarthet, F. Lagugné; Buffeteau, and T.; Sourisseau, C.

doi:10.1021/jp980859r

Cited by 60 publications

(78 citation statements)

References 47 publications

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“…At present, we can only speculate on the reason for the periodic adhesion variations. The most promising candidate is again the orientational distribution of chromophores, which results from competition between the light‐induced and flow‐induced orientations (Geue et al ., 1997; Lagugne‐Labarthet et al ., 1998). Depending on the preferential orientation at the particular local position, highly anisotropic azobenzene moieties can impose different attractive interactions onto the cantilever tip.…”

Section: Resultsmentioning

confidence: 99%

Optical patterning in azobenzene polymer films

Stiller

Geue

Morawetz

et al. 2005

Journal of Microscopy

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SummaryThin azobenzene polymer films show a very unusual property, namely optically induced material transport. The underlying physics for this phenomenon has not yet been thoroughly explained. Nevertheless, this effect enables one to inscribe different patterns onto film surfaces, including one-and two-dimensional periodic structures. Typical sizes of such structures are of the order of micrometers, i.e. related to the interference pattern made by the laser used for optical excitation. In this study we have measured the mechanical properties of one-and two-dimensional gratings, with a high lateral resolution, using force -distance curves and pulse force mode of the atomic force microscope. We also report on the generation of considerably finer structures, with a typical size of 100 nm, which were inscribed onto the polymer surface by the tip of a scanning near-field optical microscope used as an optical pen. Such inscription not only opens new application possibilities but also gives deeper insight into the fundamentals physics underlying optically induced material transport.

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Section: Resultsmentioning

confidence: 99%

Optical patterning in azobenzene polymer films

Stiller

Geue

Morawetz

et al. 2005

Journal of Microscopy

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“…For systems showing uniaxial symmetry, the order parameters P 2 and P 4 , the first two coefficients of the expansion in Legendre polynomials of the orientation distribution function, can be calculated by Raman spectromicroscopy (39,41,42). The method used is applicable to vibrational mode for which the Raman tensor is cylindrical.…”

Section: Orientationmentioning

confidence: 99%

“…Since there is no compelling argument to favor the Raman tensor of Pajcini et al (43) at the expense of that of Tsuboi et al (44), and since the orientation results are basically unaffected by the differences between the three tensors, we have decided to use the values of the order parameters obtained for a cylindrical Raman tensor, as done in previous studies (39,45). The calculation procedure is based on the measurement of four polarized spectra by Raman spectromicroscopy in the backscattering configuration (39,41,42). From these spectra, two intensity ratios for a given band…”

Section: For a Cylindrical Tensorþmentioning

confidence: 99%

Protein Secondary Structure and Orientation in Silk as Revealed by Raman Spectromicroscopy

Lefèvre

Rousseau

Pézolet

2007

Biophysical Journal

385

397

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Taking advantage of recent advances in polarized Raman microspectroscopy, and based on a rational decomposition of the amide I band, the conformation and orientation of proteins have been determined for cocoon silks of the silkworms Bombyx mori and Samia cynthia ricini and dragline silks of the spiders Nephila clavipes and Nephila edulis. This study distinguished between band components due to beta-sheets, beta-turns, 3(1)-helices, and unordered structure for the four fibers. For B. mori, the beta-sheet content is 50%, which matches the proportion of residues that form the GAGAGS fibroin motifs. For the Nephila dragline and S. c. ricini cocoon, the beta-sheet content (36-37% and 45%, respectively) is higher than the proportion of residues that belong to polyalanine blocks (18% and 42%, respectively), showing that adjacent GGA motifs are incorporated into the beta-sheets. Nephila spidroins contain fewer beta-sheets and more flexible secondary structures than silkworm fibroins. The amorphous polypeptide chains are preferentially aligned parallel to the fiber direction, although their level of orientation is much lower than that of beta-sheets. Overall, the results show that the four silks exhibit a common molecular organization, with mixtures of different amounts of beta-sheets and flexible structures, which are organized with specific orientation levels.

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“…They have shown that the orientation distribution of the chromophores varies spatially along the grating (i.e., whether on a hill, slope, or valley) and depends on the polarization combination used for the interfering beams. They concluded that the orientation of the chromophores is not only dictated by the spatially varying polarization of the incident irradiation but also by the mass transport of the polymer chains . They also reported differences in dye concentration between the hills and the valleys of an SRG .…”

Section: All‐optical Mass Transport Of Materialsmentioning

confidence: 99%

Taming Macromolecules with Light: Lessons Learned from Vibrational Spectroscopy

Vapaavuori

Bazuin

Pellerin

2017

Macromol. Rapid Commun.

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application of vibrational spectroscopy to rotaxane-based molecular machines, [11] molecular motors, [12] and molecule-based electronics, such as molecular electronic switches, [13] are highly recommended.In this feature article, we will focus on one of the most commonly used photoswitches, both for materials engineering and biological applications, namely, azobenzene. [14] This motif is known to change its geometry upon illumination with ultraviolet or visible light, in a socalled photoisomerization reaction from the thermodynamically stable trans conformation to the bent cis conformation (Figure 1a). [15,16] This reaction can be used to both decrease and destroy existing order in materials, as in the cases of photoinduced unfolding of azobenzenecrosslinked alpha-helical peptides, [17] photo induced nematic-isotropic phase transitions [18] and isothermal solid-toliquid transitions, [19] or, on the contrary, to induce order and anisotropy in initially isotropic or less ordered materials, such as in photoinduced birefringence, photoinduced chirality, alloptical poling, and surface relief grating (SRG) formation. [2,20,21] The photoisomerization of individual azobenzene moieties is known to occur in the picosecond timescale and results in changes in its molecular dimensions and properties, such as its dipole moment, solubility and UV-vis absorption. [15] Apolar azobenzene molecules typically have well isolated cis and trans absorption bands along with long thermal cis lifetimes. They are therefore suitable for optical switching applications where two "stable" long-lived states are required. By contrast, functionalizing azobenzene molecules with electron donating and electron withdrawing substituents (or push-pull substitution) alters their photochemistry, typically leading to an overlap of cis and trans absorption bands and thus to quasi-continuous photoswitching between the trans and the cis geometrical isomers. [15,16] Examples of drastic changes in material systems resulting from bistable photoswitching between trans and long-lived cis isomers are illustrated in Figure 1b-d and include photoswitching of the tilt of liquid crystals by an azopolymer command layer, [22] the light-powered contraction of a helical ribbon of a liquid crystalline azopolymer, mimicking plant tendrils, [23] and the photoinduced decrease in helix content of a peptide cross-linked by an azobenzene. [17] Demonstrations of the use of continuous azobenzene photoswitching between the two geometrical isomers, shown in Figure 1e

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Molecular Orientations in Azopolymer Holographic Diffraction Gratings as Studied by Raman Confocal Microspectroscopy

Cited by 60 publications

References 47 publications

Optical patterning in azobenzene polymer films

Optical patterning in azobenzene polymer films

Protein Secondary Structure and Orientation in Silk as Revealed by Raman Spectromicroscopy

Taming Macromolecules with Light: Lessons Learned from Vibrational Spectroscopy

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