Nanosecond laser-induced periodic surface structuring of cross-linked azo-polymer films

• Published in: Applied surface science Vol. 282; pp. 880 - 886
• Main Authors: Berta, Marco, Biver, Émeric, Maria, Sébastien, Phan, Trang N.T., D’Aleo, Anthony, Delaporte, Philippe, Fages, Frederic, Gigmes, Didier
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-10-2013; Elsevier
• Subjects: Azo; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Copolymers; Cross-disciplinary physics: materials science; rheology; Crosslinking; Engineering Sciences; Exact sciences and technology; Formations; Holes; Isomerism; Laser ablation; Lasers; LIPSS; Nanostructure; Optics; Photonic; Physics; Ripples; Scission; Unpolarized laser; Ripples; LIPSS; Isomerism; Unpolarized laser; Azo; Laser radiation; Physical radiation effects; Polymer films
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2013.06.074

•Copolymers were cross-linked with formation of azo bonds and release of gaseous N2.•Azo groups act as chromophores upon irradiation with a 248nm KrF nanosecond laser.•The amount of initial copolymer crosslinking determines extent of LIPSS formation.
In this work we discuss the response to laser ablation of a poly(4-vinylbenzyl azide-random-methyl methacrylate) (p((S-N3)-r-MMA)) random copolymer. This material is cross-linkable thermally and upon exposure to UV light, and on cross-linked films the irradiation with a 248nm ns KrF laser induces the formation of laser induced periodical surface structure (LIPSS). The LIPSS morphology is dependent on the amount of 4-vinylbenzyl azide (S-N3) groups in the pristine copolymer. We propose a crosslinking mechanism based on the scission of azide with formation of azo groups and we discuss the possible relationship between this chemical modifications and the formation of ripples on the bottom of laser ablation cavities.