Supramolecular Polymers in Aqueous Medium: Rational Design Based on Directional Hydrophobic Interactions

Abstract

Self-assembly in aqueous medium is of primary importance and widely employs hydrophobic interactions. Yet, unlike directional hydrogen bonds, hydrophobic interactions lack directionality, making difficult rational self-assembly design. Directional hydrophobic motif would significantly enhance rational design in aqueous self-assembly, yet general approaches to such interactions are currently lacking. Here, we show that pairwise directional hydrophobic/π-stacking interactions can be designed using well-defined sterics and supramolecular multivalency. Our system utilizes a hexasubstituted benzene scaffold decorated with 3 (compound 1) or 6 (compound 2) amphiphilc perylene diimides. It imposes a pairwise self-assembly mode, leading to well-defined supramolecular polymers in aqueous medium. the assemblies were characterized using cryogenic electron microscopy, small-angle X-ray scattering, optical spectroscopy, and EPR. Supramolecular polymerization studies in the case of 2 revealed association constants in 10(8) M(-1) range, and significant enthalpic contribution to the polymerization free energy. The pairwise PDI motif enables exciton confinement and localized emission in the polymers based on 1 and 2's unique photonic behavior, untypical of the extended π-stacked systems. Directional pairwise hydrophobic interactions introduce a novel strategy for rational design of noncovalent assemblies in aqueous medium, and bring about a unique photofunction.

Perylene Bisimide Dye Assemblies as Archetype Functional Supramolecular Materials

“…These assemblies revealed exciton confinement and localized emission, which are uncommon for extended π-stacked systems. 284 In another study, Yagai and co-workers reported on the selfassembly of bis-PBIs 3-38a−f (n = 5−10), which were connected through alkane linkers to control self-organized structures in both solution and solid state. 285 An odd/even effect of the linker units was observed due to the different molecular packing efficiencies, which influence the thermal as well as electronic properties and charge-carrier transportation characteristics of these bis-PBIs.…”

Constitutional Dynamic Materials—Toward Natural Selection of Function

“…103 A rational design of supramolecular dynamers based on hydrophobic interactions has been realized in recent years. 104 Hexasubstituted benzene scaffolds decorated with amphiphilic perylene diimides (64 or 65) were observed to self-assembly into supramolecular polymers through pairwise hydrophobic/ π-stacking interactions in aqueous medium ( Figure 36). The association constants of 65 were determined to be as strong as 10 9 M −1 .…”

Nanosheets of an Organic Molecular Assembly from Aqueous Medium Exhibit High Solid‐State Emission and Anisotropic Charge‐Carrier Mobility

“…The temperature dependent UV-vis absorption study performed in water: acetonitrile (ACN) (90:10) at a concentration of 3 × 10 -5 m revealed a cooperative pathway ( Figure S5d, Supporting Information). [45] Clear lattice planes were observed for the assembly in water with a d-spacing of 3.6 Å under high resolution TEM (inset Figure 2c). The transmission electron microscopy (TEM) images of PDPP-Amphi aggregates in MCH: chloroform (95:5) as well as in water: ACN (90:10) mixtures (5 × 10 -5 m) obtained upon drop casting over carbon coated copper grids are shown in Figure 2c.…”