Thin Molecularly Imprinted Polymer Films via Reversible Addition−Fragmentation Chain Transfer Polymerization

Abstract

Mesoporous silica beads modified with an azo initiator were used for grafting of cross-linked molecularly imprinted polymers through reversible addition−fragmentation chain transfer (RAFT) mediated polymerization. The RAFT mediation allowed an efficient control of the grafting process and led to suppression of the solution propagation preventing any visible gel formation. Thus, graft copolymerization of methacrylic acid and ethylene glycol dimethacrylate using 2-phenylprop-2-yl-dithiobenzoate as the chain transfer agent and in the presence of l-phenylalanine anilide as the template led to imprinted thin film composite beads. The resulting composites were characterized by Fourier transform infrared spectroscopy, nitrogen sorption analysis, elemental analysis, fluorescence microscopy, and scanning electron microscopy and as stationary phases in chromatography. This indicated the presence of thin homogeneous films (thickness: 1−2 nm) containing imprinted sites for the template (l-phenylalanine anilide). The resulting materials proved to be highly selective chiral stationary phases resulting in baseline separations of the template racemate and of structurally analogous racemates within a few minutes. These results were comparable with results obtained for materials prepared in the absence of RAFT mediation with the notable difference being the absence of detectable solution gelation using RAFT.