Periodic mesoporous organosilicas from polyion complex micelles : effect of organic bridge on nanostructure

A new family of polyion complex (PIC)-based periodic mesoporous organosilicas, PICPMOs, obtained by the hydrolysis-condensation of organosilanes containing organic bridging units (phenylene, ethenylene and ethylene) in the presence of polyion complex (PIC) micelles as structure-directing agents (SDAs), is described. The electrostatic interactions between the acrylic acid functions of a poly(ethylene oxide)-b-poly(acrylic acid) double-hydrophilic block copolymer (DHBC) and the primary amine functions of a polyamine micellization agent control the formation of the core of the micellar complex, while the PEO chains of the micelle corona mediate the formation of the organic/inorganic interface that controls the evolution of the material. Herein, the micellization agent employed is an antibiotic drug, neomycin B. An important feature of this procedure is that the processing involves a "one-pot" reaction, enabling the formation of the material and the direct encapsulation of the anti-bacterial agent. This results in a reduction in the number and cost of processing steps, while offering the opportunity to easily tune the hybrid mesostructure. The PICPMO materials obtained are organized on different length scales, from long-range-ordered 2D hexagonal structuring in the case of the phenylene bridge to weakly organized wormlike structures in the case of the ethylene unit. The effect of organic bridge structure on the nanostructure and physical properties of the PICPMO is discussed.