Spontaneous photoinduced patterning of azo-dye polymer films: the facts

Two-Photon Induced Self-Structuring of Polymeric Films Based on Y-Shape Azobenzene Chromophore

“…However, this technique still suffers of long processing time of the order of hours for patterned areas of a few mm 2 . 12,22 In this work, we study the self-structuring of an azo-polymer containing Y-shaped chromophores, designed and synthesized to optimize TPA. The exposure of the free surface of the polymer films to a single, normally incident, focused femtosecond laser beam (λ = 800 nm) induces mass migration activated mainly by TPA.…”

Spontaneous Formation of Complex Periodic Superstructures under High Interferential Illumination of Small‐Molecule‐Based Photochromic Materials

“…[25,26] However, in both cases, the irradiation intensity that was set at above 300 mW cm À2 created complex periodic patterns of a muchsmaller amplitude (500 nm high for 2 mmthick doped elastomer films [25] and 100 nm for 220-nm-thick DR1-PMMA films [26] ) with no evidence of a complete depletion of the azo material in the grooves. Indeed, wide-field optical imaging during the irradiation of the CarbCN thin films showing the most prominent superstructures identifies that all of the protuberances precisely rose from the top of the gratings formed in the first period (Fig.…”

“…The assumption following which their appearance might be driven by photoinduced anisotropic viscoelasticity, [24,25,27] temperature-gradient effects [25] or optical effects [26,28] such as diffraction or reflection, is fiercely debated among authors. Feedback effects based on the reflection of the first-order diffracted beam from the reverse side of the glass substrate has been proposed by Nunzi et al to explain the orthogonal patterns observed, whereas thermal-gradient influence has been discarded on the grounds of a macroscopic temperature rise that is much lower than the polymer T g itself.…”

“…Feedback effects based on the reflection of the first-order diffracted beam from the reverse side of the glass substrate has been proposed by Nunzi et al to explain the orthogonal patterns observed, whereas thermal-gradient influence has been discarded on the grounds of a macroscopic temperature rise that is much lower than the polymer T g itself. [26,29] If such assumptions were valid, changes in the interfringe spacing by varying the crossing angle u between both interfering beams should produce a comparable change in the distance between the stripe-like superstructures according to the Bragg's law L ¼ 2lsin u where u, L and l designate the incidence angle, the interfringe spacing and the illumination wavelength respectively. In our case, changing u from 17 8 to 11 8 actually enlarged L from 0.84 mm to 1.30 mm while the distance between two consecutive stripes only increased from 3.42 mm to 4.00 mm (Fig.…”

Light-Triggered Formation of Surface Topographies in Azo Polymers

“…Interestingly, for the small chains, they found a secondary profile perpendicular to the grating wave-vector with modulation depth up to 200 nm (Figure 5b). The origin of this additional periodic topography is not clearly understood, but can be found in several examples [62][63][64][65][66]. Santer and co-workers have developed a method that allows in-situ atomic force microscopy during the formation of SRGs in azo-polymers.…”