Photoinduced supramolecular chirality and spontaneous surface patterning in high-performance azo materials

Bagatur, Sekvan; Fuhrmann‐Lieker, Thomas

doi:10.1186/s41476-019-0104-5

Cited by 4 publications

(7 citation statements)

References 22 publications

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“…This explains the significant high optical rotations of polymers P2 and P3 (cf. [ 28 ]). The comparison between homopolymer P2 and copolymer P3 shows that the bicyano substitution at the three-core side-chain leads to more advantageous behavior for PSC than the monocyano substitution.…”

Section: Discussionmentioning

confidence: 99%

“…It seems that anisotropic surface structures, which can be imagined as 2D-chiral surfaces (see [ 24 ]), contribute to azimuthal rotation. The difference between irradiating azo and glass-side is discussed more detailed in [ 28 ].…”

Section: Discussionmentioning

confidence: 99%

“…These polymers are characterized by their extend conjugated

-electron system and the push-pull substitution by amine and (bi)cyano groups. Since we are interested in reaching high azimuthal rotations, Polymer P1 as used in [ 28 ] with a nitro-substituent was excluded because of its low values for azimuthal rotation. This behavior is explainable by its comparatively lower polarizability due to the smaller two-core

-electron system.…”

Section: Methodsmentioning

confidence: 99%

“…An exemplary comparison of literature values for the azimuthal rotation in relation to its layer thickness d shows the following measured values:

[ 15 ],

[ 20 ],

[ 18 ],

[ 19 ]. Recently, we measured a very high azimuthal rotation with a value of

[ 28 ]. In relation to its film thickness, the rotation amounts

.…”

Section: Introductionmentioning

confidence: 99%

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Polarization Dependent Photoinduced Supramolecular Chirality in High-Performance Azo Materials

2021

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Here, we will show photo-induced supramolecular chirality in thin films of achiral amorphous polymers with azo groups in their side-chain. A matter of particular interest is the effect of various film thicknesses on azimuthal rotation and ellipticity of incident/transmitted polarized light. Furthermore, we investigated the temporal stability of inscribed chirality. By polarimetric measurements, we found out that the azimuthal rotation gets higher with layer thickness. In this scope, we were able to measure a very high azimuthal rotation of Δψ/d=112.5∘/μm. The inscribed chirality was stable for several days. Furthermore, we investigated the time-resolved behavior of incident and transmitted polarization ellipticities for various thicknesses. The time dependency may be explained by a two-step process: (1) fast trans-cis-isomerization resulting in photo-orientation and (2) slow photo-induced mass flow.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…These polymers are characterized by their extend conjugated

-electron system.…”

Section: Methodsmentioning

confidence: 99%

“…An exemplary comparison of literature values for the azimuthal rotation in relation to its layer thickness d shows the following measured values:

[ 15 ],

[ 20 ],

[ 18 ],

[ 19 ]. Recently, we measured a very high azimuthal rotation with a value of

[ 28 ]. In relation to its film thickness, the rotation amounts

.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Polarization Dependent Photoinduced Supramolecular Chirality in High-Performance Azo Materials

2021

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“…for organic glasses or polymers by heating the central layer above glass transition temperature whereas the cladding layer remains solid and prevents spinodal dewetting and thus, makes thermal wrinkling possible. Also, photoinduced approaches have been reported [36][37][38] . The morphology, the spatial wavelength Λ and the dynamics are controlled by the mechanical properties of the materials, the film thicknesses, intrinsic stresses due to the preparation as well as by the treatment for relaxation.…”

Section: Two-dimensional Wrinklementioning

confidence: 99%

Two-dimensional Wrinkle Resonators for Random Lasing in Organic Glasses

Hoinka

Ostwald

Fuhrmann‐Lieker

2020

Sci Rep

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Random lasers consisting of slab waveguides with two-dimensional disordered wrinkling patterns that act as scattering resonators are reported. As active material 2,2′,7,7′-tetraphenyl-9,9′-spirobifluorene is used which is sandwiched between an oxidized silicon wafer and a cladding with higher glass transition temperature. Wrinkles with tailorable periodicity have been induced by thermal annealing. Photopumping experiments show the transition from amplified spontaneous emission to a multiple peak laser spectrum with linewidths as low as 0.1 nm, demonstrating the applicability of this approach for random laser design.The phenomenon of random lasing has resurrected great interest recently, after its theoretical postulation 1 and experimental realization in a variety of systems 2-6 , including dye containing liquids 7,8 , powders 2,9 , scattering enhancing liquid crystals 10,11 and especially polymer-based dye-doped waveguide materials 6,12-16 . Polymers provide flexible, low cost materials with a spectral range only limited by the gain material used as dopant.Random lasing is based on amplified emission and multiple scattering in disordered media and, in literature, it is classified depending on the present feedback mechanism in either incoherent or coherent random lasing. The latter results in sharp lines based on resonant feedback loops and exist both in strongly scattering, localized regimes and in weakly scattering, diffusive regimes. Incoherent random lasers, or non-resonant feedback lasers are terms that represent a variety of light amplifications in disordered media, but they have neglectable feedback and result in a smooth, broader amplification peaks (several nm). In organic photonics, thin waveguide structures are popular for lasing devices due to easy manufacturing techniques and their compatibility with integrated optics [17][18][19] . The confinement that is introduced by the waveguide structure is often sufficient for non-resonant stimulated emission in organic laser dyes called ASE or "travelling wave lasing" without the necessity of additional confinement by a resonator, when gain is introduced. A key aspect is that the gain length needs to be large enough to exceed the losses which defines the threshold of ASE in waveguiding structures 20,21 . Similar to non-resonant feedback lasing, it results in drastic spectral narrowing for fluences above threshold. Consider a waveguide structure in an intermediate regime between slight disturbances on the surface due to increased roughness and increasing backscattering in analogy to quasi-waveguides which show losses introduced by uneven substrates. Here, the modes can still travel through the sample only that scattering at the surface is introduced. Such lossy, asymmetric slab guide systems have already been reported 13,15,16 and light amplification might be introduced due to both multiple scattering and waveguiding in a still confined, but lossy slab guide structure. For the non-resonant case, we refer to this type of emission as amplified spontaneous emissio...

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