Polarized 3D Raman and nanoscale near-field optical microscopy of optically inscribed surface relief gratings: chromophore orientation in azo-doped polymer films

Florio, Giuseppe Di; Bründermann, Erik; Yadavalli, Nataraja Sekhar; Santer, Svetlana; Havenith, Martina

doi:10.1039/c3sm51787j

Cited by 22 publications

(23 citation statements)

References 54 publications

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“…The light‐driven phenomena like molecular photoorientation, photo‐induced mass transfer, generation of mechanical forces, and so on have been used extensively to create various functional materials for optics, photonics, and soft‐robotics . Particularly, azobenzene‐based polymers are increasingly drawing attention of the scientific community as materials for the holographic data storage and the recording of a wide range of diffraction gratings (polarized gratings, surface relief gratings, reflection gratings, and so on) . In contrast to amorphous polymers, which are mostly interesting for the fabrication of surface relief gratings, liquid crystalline (LC) polymers are suitable for a polarization grating recording due to their high optical birefringence and cooperativity at the molecular level .…”

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confidence: 99%

Polarization Gratings in Azobenzene‐Based Fully Liquid Crystalline Triblock Copolymer

Bugakov

Sakhno

Boiko

et al. 2019

Macromol. Rapid Commun.

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surface relief gratings, liquid crystalline (LC) polymers are suitable for a polarization grating recording due to their high optical birefringence and cooperativity at the molecular level. [15] The majority of recent reports on this kind of materials concern LC homopolymers, random copolymers, and block copolymers that contain azobenzene and amorphous blocks. In block copolymers, the formation of an LC phase competes with the nanoscale segregation of constituent blocks. It yields synergy of various nanostructures such as spheres, cylinders and lamella, and properties of an LC phase (a cooperative molecular motion and high anisotropy of physical parameters). [16,17] In addition, due to the formation of a microphase-separated structure, the local concentration of azobenzene groups in block copolymer films is as high as in azobenzene homopolymers. It can provide considerable faster recording and higher efficiency in comparison with random copolymers. [18] To date the holographic recording in LC block copolymers containing azobenzene and amorphous blocks has been studied extensively. [17][18][19][20][21][22] Amorphous blocks of such block copolymers do not contribute to the optical response and do not participate in the holographic recording. On the other hand, introducing LC (mesogenic) groups in each block of block copolymers assures controlling optical properties of every microphase. [23] The presence of mesogenic groups in each block may bring into a play the whole polymer volume, thus increasing efficiency of these materials from the standpoint of the holographic recording. However, there is only one short mention concerning the holographic recording in films of azobenzene LC diblock copolymers comprised of only mesogenic monomer units. [24] Although fully LC block copolymers are envisioned as novel efficient materials for the holographic recording, such copolymers are far from being elucidated properly.In our previous work, we have synthesized LC photo sensitive ABA triblock copolymers comprised of azobenzene (Azo) and non-photosensitive phenyl benzoate (PhM) units. [23] We have also demonstrated that the irradiation of these materials with linearly polarized light and subsequent annealing offer an efficient tool for the selective control over the orientation of Azo and PhM groups. [25] In this communication, we aim to study holographic behavior of fully LC ABA triblock copolymer (Block) composed of Azo and PhM mesogenic units (Figure 1a) with the focus on polarization holographic gratings. As reference samples, Photosensitive liquid crystalline (LC) block copolymers are a universal platform for designing functional materials for optics and photonics. Here, azobenzene LC ABA triblock copolymer containing mesogenic groups in each block is studied as a medium for the recording of polarization holographic gratings. The fast recording of polarization gratings is successfully performed with two orthogonally circularly polarized light beams of a 532-nm laser. It is shown that annealing of the recorded polarization g...

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confidence: 99%

Polarization Gratings in Azobenzene‐Based Fully Liquid Crystalline Triblock Copolymer

Bugakov

Sakhno

Boiko

et al. 2019

Macromol. Rapid Commun.

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“…Raman spectroscopy was used to identify the signature of the aromatic azo group grafted on the polyimide chains before and after irradiation. According to literature data, the azo (-N=N-) stretching band (-N=N-) has strong intensity with the trans form absorbing in the range of 1465-1380 cm −1 and cis form around 1510 cm −1 [73,74].…”

Section: Evaluation Of the Local Chemical Propertiesmentioning

confidence: 80%

Evaluation of Local Mechanical and Chemical Properties via AFM as a Tool for Understanding the Formation Mechanism of Pulsed UV Laser-Nanoinduced Patterns on Azo-Naphthalene-Based Polyimide Films

Stoica¹,

Epure

Constantin³

et al. 2021

Nanomaterials

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Aromatic polyimides containing side azo-naphthalene groups have been investigated regarding their capacity of generating surface relief gratings (SRGs) under pulsed UV laser irradiation through phase masks, using different fluencies and pulse numbers. The process of the material photo-fluidization and the supramolecular re-organization of the surface were investigated using atomic force microscopy (AFM). At first, an AFM nanoscale topographical analysis of the induced SRGs was performed in terms of morphology and tridimensional amplitude, spatial, hybrid, and functional parameters. Afterward, a nanomechanical characterization of SRGs using an advanced method, namely, AFM PinPoint mode, was performed, where the quantitative nanomechanical properties (i.e., modulus, adhesion, deformation) of the nanostructured azo-polyimide surfaces were acquired with a highly correlated topographic registration. This method proved to be very effective in understanding the formation mechanism of the surface modulations during pulsed UV laser irradiation. Additionally to AFM investigations, confocal Raman measurements and molecular simulations were performed to provide information about structured azo-polyimide chemical composition and macromolecular conformation induced by laser irradiation.

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“…The formalism developed by Sourisseau and co‐workers was further applied by Havenith and co‐workers to study the chromophore orientation at different locations of SRGs prepared using various interference patterns . Among these, they found anisotropic orientation distributions in the areas subjected to circular polarization under a ±45° interference pattern, suggesting that the mass transport itself contributes to the orientation (uniform illumination with circular polarization maintaining in‐plane isotropy, as discussed in Section ).…”

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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Polarized 3D Raman and nanoscale near-field optical microscopy of optically inscribed surface relief gratings: chromophore orientation in azo-doped polymer films

Cited by 22 publications

References 54 publications

Polarization Gratings in Azobenzene‐Based Fully Liquid Crystalline Triblock Copolymer

Polarization Gratings in Azobenzene‐Based Fully Liquid Crystalline Triblock Copolymer

Evaluation of Local Mechanical and Chemical Properties via AFM as a Tool for Understanding the Formation Mechanism of Pulsed UV Laser-Nanoinduced Patterns on Azo-Naphthalene-Based Polyimide Films

Taming Macromolecules with Light: Lessons Learned from Vibrational Spectroscopy

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