Pyrene-Based Co-Assembled Supramolecular Gel; Morphology Changes and Macroscale Mechanical Property

Abstract

Two pyrene derivatives having the perylenediimide (<b>1</b>) or the alky chain (<b>2</b>) in the middle of molecules were synthesized. Co-assembled supramolecular gels were prepared at different molar ratios of 0.2, 0.5, and 0.8 equiv. of <b>2</b> to <b>1</b>. By SEM observation, the morphology of co-assembled supramolecular gels changed from spherical nanoparticles to three-dimensional network nanofibers as the ratio of <b>2</b> increased. In addition, the pyrene-excimer emission of co-assembled gels increased with increasing concentration of <b>2</b>, and was stronger when compared with the condition without <b>1</b> or <b>2</b>, indicating the formation of pyrene interaction between <b>1</b> and <b>2</b>. In addition, the sol-gel transition was found to be reversible over repeated measurement by tube inversion method. The rheological properties of co-assembled supramolecular gels were also improved by increasing the ratio of <b>2</b>, due to the increased nanoscale flexibility of supramolecular packing by introducing alkyl chain groups through heterogeneous pyrene interaction. These findings suggest that macroscale mechanical strength of co-assembled supramolecular gel was strongly influenced by nanoscale flexibility of the supramolecular packing.