Azo-polysiloxanes spontaneous surface relief grating by pulsed laser irradiation
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Azo‑polysiloxanes spontaneous surface relief grating by pulsed laser irradiation G. Bulai1 · L. Epure2 · M. Strat3 · S. Toma4 · N. Cimpoesu4 · S. Gurlui3 · R. Constantinel2 · N. Hurduc2 Received: 7 April 2020 / Accepted: 11 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract In the herein paper, the possibility of obtaining spontaneous surface relief gratings (SSRGs) on azo-polymeric film surfaces, using a single laser beam of 1.13 mJ energy in pulse mode, was investigated. Chain rigidity is essential to have SSRG of reasonable quality so three azo modified polymers, with different main-chain rigidity, were considered: poly(chloromethyl styrene) (PCMS), a linear polysiloxanes and a cyclic polysiloxane. The AFM studies on azo-polysiloxanes revealed unregulated networks with amplitudes of only 1 nm, while on PCMS orderly SSRGs were observed. These results showed that the more rigid azo-polymer, PCMS, had better capacity to generate SSRGs of high quality. The SSRG periodicity was correlated with the number of laser pulses, i.e. higher pulse number led to lower periodicity. The SSRGs formation was associated with polymeric chains self-organization favoured by photo-fluidisation. Keywords Azo-polymers · Surface relief gratings · Polysiloxane · Laser · Nanostructuration
1 Introduction The azo-materials capability to generate surface relief gratings (SRGs) by interacting with laser beams has captivated the attention of many researchers in the last period, due to their interesting applications like data storage, holography, display technology, support for cell cultures, solar energy, or intelligent coatings [1–11]. Accountable for the surface nanostructuration are the azobenzene groups, which change their configuration reversibly from trans to cis, as result of interaction with light. The origin
* N. Hurduc [email protected] 1
Integrated Center for Studies in Environmental Science for North‑East Region (CERNESIM), “Alexandru Ioan Cuza” University of Iasi, 700506 Iasi, Romania
2
Department of Natural and Synthetic Polymers, Gheorghe Asachi Technical University of Iaşi, Bd. Prof. D. Mangeron 73, 700050 Iasi, Romania
3
Faculty of Physics, Atmosphere Optics, Spectroscopy and Lasers Laboratory, “Alexandru Ioan Cuza” University of Iasi, 700506 Iasi, Romania
4
Faculty of Material Science and Engineering, Technical University Gheorghe Asachi of Iași, Dimitrie Mangeron Street, No. 67, 700050 Iasi, Romania
of nanostructuration processes is not yet clarified, even if more than 20 years have passed since first report of the phenomenon [12, 13]. Several models have been proposed to describe the course of the process (isomerization pressure, gradient electric force, permittivity gradient, asymmetric diffusion, mean-field model, theory of light-induced deformation, cage-breaking model, statistical model based on fundamental molecular dipole), but none of them succeeded to completely explain the surface relief formation [14–23]. Under continuous laser irradiation permanent trans–
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