Surface relief gratings induced by pulsed laser irradiation in low glass‐transition temperature azopolysiloxanes

Abstract

Polymers capable of generating surface relief gratings (SRGs) were studied intensively in the last period for their applications in hot research areas, such as data storage, solar energy conversion, plasmonics, and biology. In the case of azopolymers, SRGs can be generated by two main procedures: pulsed or continuous laser irradiation. In this article, we discuss the possibility of obtaining stable SRGs with azopolysiloxanes with low glass‐transition temperature values, depending on the illumination type. These studies evidenced that the polymer chemical structure had a strong influence on the SRG stability in time. For the unsubstituted azobenzene, unstable surfaces resulted, whereas for the substituted azo groups stable reliefs were obtained. A parallel discussion between the pulsed and continuous irradiation techniques and structuration mechanisms is given. The operational conditions strongly affected the relief quality when the pulsed laser irradiation method was used. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41015.

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

“…Because of the very short irradiation times (6 nanoseconds) used in the pulsed mode, the mechanism responsible for the periodic SRGs profile generation involves the fringe pattern produced by the interference of the diffracted beams. They act through two possible mechanisms, namely, a very fast supramolecular reorganization process, induced by the azo-groups dipole orientation [ 50 ], and material photo-fluidization, induced by the trans–cis isomerization process of the azo-segments in the exposed regions [ 20 , 24 , 51 ]. This competes with the larger proper volume required by the cis conformation [ 52 ].…”

“…Mainly, this mass displacement can take place from UV laser-exposed areas to the unexposed areas. Recently, it was demonstrated that also an inverse mass displacement can occur, from the dark regions to the illuminated ones [ 24 ]. The arguments for the development of the azobenzene photoisomerization process by inversion or rotation are the subject of numerous molecular simulation studies [ 25 , 26 , 27 , 28 ].…”

“…In the case of continuous laser irradiation, the apexes of the sinusoidal surface relief appeared in the unexposed regions. When pulsed UV laser irradiation was employed, the positions of the apexes were dependent on the laser fluence, being in the exposed regions when the fluence value was below a threshold, and in the unexposed regions when the fluence value was above this threshold, as mentioned in the literature data [ 24 ]. In a pulsed laser regime, the relief geometric parameters depend on several factors.…”

Liquid‐crystalline and photo‐induced properties of P4VP quaternized with bromo derivative of dialkyloxy‐phenyleneazobenzene groups

“…Each one of these two features is useful to orient the azo‐mesogenic groups into a specific direction, and thus induce properties of practical interest like birefringence, dichroism and chirality, among others. Moreover, the photo‐isomerization is helpful to induce a mass migration in thin or thick films, leading to the formation of micro‐scale surface relief gratings (SRG) of regular profile . Both, the light‐induced orientation and mass migration make the liquid crystal azopolymers potential candidates for many applications, particularly for volume or high density (terabytes) data storage memories.…”

Optical Patterning of Sol–Gel Silica Coatings

“…[9][10][11][12][13] In this case, direct and effi cient optical inscription of relief patterns can be achieved on thin azo-fi lms by a spatially modulated illumination. [9][10][11][12][13] In this case, direct and effi cient optical inscription of relief patterns can be achieved on thin azo-fi lms by a spatially modulated illumination.…”