PEGylated perylene bisimides: Chromonic building blocks for the aqueous synthesis of nanostructured silica materials

Abstract

Perylene dyes have applications in many fields. Herewith, we report on the synthesis and properties of a series of PEGylated perylene bisimides with varying PEG chain lengths. Such molecules are formed by a hydrophobic perylene core functionalized at the imide positions with hydrophilic non-ionic functional groups, which impart solubility and capacity to self-assemble in water. The diluted solutions of the synthesized molecules show interesting optical and fluorescent properties that depend on solvent and concentration; they also show surface activity and a lower critical solution temperature. Moreover, at high concentrations, the molecules produce lyotropic chromonic liquid crystals with nematic and hexagonal structures, formed by aligned molecular stacks. Such mesostructures were successfully exploited for the preparation of hybrid silica materials with ordered perylene nanostripes that generate aligned nanopores (of ca. 1.4 nm) upon calcination. It was found that the distance between perylene nanostripes and hence the pore wall thickness can be finely tuned by changing the length of the PEG chain.