Résumé
Polyion complex (PIC) micelles are highly efficient agents for directing the structure of silica. They are particularly attractive because they enable the direct preparation of functional mesostructured materials by anchoring one of the two micellar constituents in the silica network, while allowing the other one to be released for recycling or for use in specific applications. Notably, the formation of these hybrid materials proceeds in a one-pot process under moderately acidic conditions. Despite their versatility and broad range of potential applications, their formation mechanisms have not yet been elucidated. In this work, we used in situ SAXS experiments to monitor the formation kinetics of a mesoPIC material formed from a polyion complex composed of poly(ethylene oxide)-b-poly(acrylic acid) (PEO-b-PAA) as a double hydrophilic block copolymer (DHBC) and neomycin (NM) as a micellizing agent. The results were benchmarked against the well-known SBA-15 silica material made with P123 copolymer, due to the similarity of the neutral poly(ethylene oxide) chain interacting with silica. The mechanisms of formation of the mesoPIC material resembles those already reported, involving the growth of silica oligomers and their integration into the micelle corona, followed by the formation of a 2D-hexagonal hybrid mesophase. Interestingly, a transient signal was detected during the kinetics, attributed to the formation of poorly organized packed silica-rich micelles present in large grain mesostructured material. The well-ordered final mesostructure together with the emergence and disappearance of the transient signal highlight the ability of the PIC system to reorganize dynamically into highly ordered mesostructured materials.