Influence of solvent on the supramolecular architectures in molecular gels

Abstract

Elucidating the molecular structures, responsible for promoting self-assembly of low-molecular weight organogelators (LMOG) into supramolecular fibers, has been an extensive area of study. Although this has been a fruitful endeavor, this study illustrates that the chemical nature of the solvent and solvent–gelator interactions are equally important. The nanostructure, microstructure and supramolecular structures, of 12HSA molecules gels, are all influenced by the chemical nature of the solvent, which correlate to the hydrogen-bonding Hansen solubility parameter (∂_h). Depending on the solvent employed, the polymorphic form, arrangement of the carboxylic acid dimers, domain size, fiber morphology, microstructure, thermal properties and visual appearance of the gel all differ. Solvents that have δ_h < 4.4 MPa^1/2, result in a hexagonal polymorphic form, with an 001 hlk spacing greater than the extended bi-molecular length of 12HSA. This nanoscale arrangement results in translucent gels that contain fibrillar aggregates corresponding to a higher crystallinity compared to molecular gels formed in solvents that have a δ_h > 4.4 MPa^1/2.