Photografting as a versatile, localizable, and single-step surface functionalization of silica-based monoliths dedicated to microscale separation techniques

In this work, we developed a surface functionalization way of silica monoliths with a rapid, simple, versatile, and localizable photografting step. The elaboration of a photoreactive layer at the surface of monoliths was first optimized. The functionalization with [gamma-(methacryloyloxy) propyl] trimethoxysilane at 80 degrees C in a hydro-organic solution containing triethylamine as catalyst allows reachng the highest density of methacrylate photoactive moieties on silica surfaces. Thesemethacrylate reactive surfaces were subsequently photografted within few minutes with acrylate monomers bearing alkyl chains (C-12 and C-18). The photografting efficiency was determined by monitoring the retentive properties ofmonoliths in the RP mode. The retention factors are of the same order of magnitude as highly retentive columns obtained bymodification of silica surface with long-alkyl chain silanes or by thermal polymerization of long-alkyl chain monomers. It was also verified that such grafting neither impaired the efficiency of the monolithic stationary phase (H-min = 6-8 mu m in nano-LC) nor its permeability (about 6 x 10(-14) m(2)). Further, it was also demonstrated that photografting is localizable in nonmasked defined areas. Results obtained in anion-exchange chromatography after photopolymerization of [2-(methacryloyloxy) ethyl] trimethylammonium chloride are presented as well to demonstrate the versatility of the developed approach.