title: 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.
authors: Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
authors: Alona
authors: A
authors: Ustinov
authors: Haim
authors: H
authors: Weissman
authors: Elijah
authors: E
authors: Shirman
authors: Iddo
authors: I
authors: Pinkas
authors: Xiaobing
authors: X
authors: Zuo
authors: Boris
authors: B
authors: Rybtchinski
mesh_terms: D001554:Benzene / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D007094:Imides / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D010569:Perylene / Q000031:analogs & derivatives* / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D007094:Imides; D011108:Polymers; C521332:perylenediimide; D014867:Water; D010569:Perylene; D001554:Benzene