Pyrrole containing ionic liquid as tecton for construction of ordered mesoporous silica with aligned polypyrrolenanowires in channels

Abstract

Two types of ionic liquid (IL) based surfactants bearing a terminal pyrrole moiety were synthesized, and used as both structure-directing agents and monomers to prepare mesostructured silica with densely packed pyrrole units within channels via a hydrothermal synthesis procedure. A systematic study was carried out to address the influence of the relative concentration of the IL and the type of head group and counter ions on the mesostructure. As a main result, it was found that both the prepared imidazolium- and pyridium-based surfactants displayed a significantly strong tendency towards formation of a highly ordered two-dimensional (2D) hexagonal mesostructure in a broad range of conditions with excellent reproducibility. In situpolymerization of the pyrrole groups closely packed in the central region of the formed silica pore channels led to the desired mesostructured silica with well-distinct aligned polypyrrole (PPy) molecular wires in channels, which are clearly visible under TEM after the removal of silica framework. It is found that, due to the spatial confinement of the silica framework, the encapsulated PPys are elongated and straight, leading to longer conjugation length.