Regulation of gel formation, hierarchical structures, rheological behavior, and surface wettability via the linker of molecule center on bis(cholesteric) derivatives supramolecular self-assembly systems

A series of novel gelators (1-3) based on bis(cholesteric) derivatives with different molecular centers were designed and characterized. Their differences in molecule structures were only the linkers of molecule center. Their self-assembly process were carefully studied through different techniques including field emission scanning electron microscope (FESEM), UV-vis absorption spectra, fourier transform infrared (FTIR) spectra, rheology, X-ray diffraction (XRD) and water contact angles. Hydrophobic interaction and weak hydrogen bonding interaction may be the main driving force for gel formation. More significant, the gelation ability, self-assembly process, rheological behavior, and surface wettability of these self-assembly systems could be adjusted via the linker of molecule center. With the flexibility of the linker increasing, the gelation ability was gradually decreased. Different self-assembly structures from microrods to nanofibers were obtained in the sol-gel transition process of compounds 1-3. J-type aggregation mode was employed in gel systems 2 and 3. Interestingly, the mechanical strength of gel systems 2 and 3 was obviously stronger than that of gel system 1 in the same solvent. Xerogel film of 2 with the "lotus effect" exhibited more hydrophobicity with contact angle of 148.5 degrees than that of xerogel films of 1 and 3. This work will bring a new method for tuning supramolecular self-assembly through the linker of molecule center.