Surface morphological modification of crosslinked hydrophilic co-polymers by nanosecond pulsed laser irradiation

• Published in: Applied surface science Vol. 369; pp. 422 - 429
• Main Authors: Primo, Gastón A., Alvarez Igarzabal, Cecilia I., Pino, Gustavo A., Ferrero, Juan C., Rossa, Maximiliano
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.04.2016
• Subjects: Copolymers; Crosslinked hydrophilic co-polymers; Crosslinking; Hydrogels; Irradiation; Laser ablation craters; Laser foaming; Lasers; Nanostructure; Surface morphological modification; Swell/dried hydrogels; Ultraviolet; UV–vis nanosecond pulsed laser irradiation; Wavelengths; Crosslinked hydrophilic co-polymers; Swell/dried hydrogels; UV–vis nanosecond pulsed laser irradiation; Laser ablation craters; Laser foaming; Surface morphological modification
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2016.02.047

•Laser-induced surface modification of crosslinked hydrophilic co-polymers by ns pulses.•Formation of ablation craters observed under most of the single-pulse experimental conditions.•UV laser foaming of dried hydrogel samples resulting from single- and multiple-pulse experiments.•Threshold values of the incident laser fluence reported for the observed surface modifications.•Lower threshold fluences for acrylate-based, compared to acrylamide-based hydrogels. This work reports an investigation of the surface modifications induced by irradiation with nanosecond laser pulses of ultraviolet and visible wavelengths on crosslinked hydrophilic co-polymeric materials, which have been functionalized with 1-vinylimidazole as a co-monomer. A comparison is made between hydrogels differing in the base co-monomer (N,N-dimethylaminoethyl methacrylate and N-[3-(dimethylamino)propyl] methacrylamide) and in hydration state (both swollen and dried states). Formation of craters is the dominant morphological change observed by ablation in the visible at 532nm, whereas additional, less aggressive surface modifications, chiefly microfoams and roughness, are developed in the ultraviolet at 266nm. At both irradiation wavelengths, threshold values of the incident laser fluence for the observation of the various surface modifications are determined under single-pulse laser irradiation conditions. It is shown that multiple-pulse irradiation at 266nm with a limited number of laser shots can be used alternatively for generating a regular microfoam layer at the surface of dried hydrogels based on N,N-dimethylaminoethyl methacrylate. The observations are rationalized on the basis of currently accepted mechanisms for laser-induced polymer surface modification, with a significant contribution of the laser foaming mechanism. Prospective applications of the laser-foamed hydrogel matrices in biomolecule immobilization are suggested.