New bolaform and trigonal cholesteryl amide derivatives with different aromatic spacers were designed and prepared. Their gelation behaviors in 20 solvents were tested as novel low-molecular-mass organic gelators (LMOGs). It was shown that the size of the spacer connecting cholesteryl residues in gelators plays a crucial role in the gelation behavior of the compounds. While the trigonal compound gels 3 of the 20 solvents tested at a concentration more than 3.0%, the bolaform compound gels 2 of the solvents tested at a concentration more than 2.0%, respectively. SEM and AFM observations reveal that the size of the spacers and the identity of the solvents are the main factors affecting the structures of the aggregates in the gels. Experimentally, a clear spacer effect on the microstructures of the gels was observed. As example, the aggregates of trigonal compound in 1,4-dioxane, aniline, or nitrobenzene adopt structures of lamella, rod, or belt, respectively. The present work may give some insight to design and character new organogelators with special molecular structures.
Keywords: Supramolecular gel, cholesterol, organogelators, spacer effect, low-molecular-mass organic gelators (LMOGs, aromatic spacers, bolaform and trigonal cholesteryl amide derivatives, solvophobic interaction