Surface Morphological Modification of Crosslinked Hydrophilic Co-Polymers by Nanosecond Pulsed Laser Irradiation

Abstract

This work reports an investigation of the surface modifications induced by irradiation with nanosecondlaser pulses of ultraviolet and visible wavelengths on crosslinked hydrophilic co-polymeric materi-als, which have been functionalized with 1-vinylimidazole as a co-monomer. A comparison is madebetween 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 532 nm,whereas additional, less aggressive surface modifications, chiefly microfoams and roughness, are devel-oped in the ultraviolet at 266 nm. At both irradiation wavelengths, threshold values of the incident laserfluence for the observation of the various surface modifications are determined under single-pulse laserirradiation conditions. It is shown that multiple-pulse irradiation at 266 nm with a limited number of lasershots can be used alternatively for generating a regular microfoam layer at the surface of dried hydro-gels based on N,N-dimethylaminoethyl methacrylate. The observations are rationalized on the basis ofcurrently accepted mechanisms for laser-induced polymer surface modification, with a significant contri-bution of the laser foaming mechanism. Prospective applications of the laser-foamed hydrogel matricesin biomolecule immobilization are suggested.