Aliphatic-Alcohol-Induced Opaque-to-Transparent Transformation and Application of Solubility Theory in a Bis-Dipeptide-Based Supramolecular Gel

Graphical Gel sensors : An opaque-to-transparent transformation of a bis-dipeptide-based supramolecular gel occurs upon use of aliphatic alcohols as a component of organic/H 2 O binary mixed solvents for gelation. A reassembly process with microstructure evolution from agglomerates to nanofibers is observed during the gel-to-gel phase transition (see figure). Moreover, the solubility theory with the Flory–Huggins parameter is used for the successful prediction of gelling performance, which could improve system screening for practical applications. A bis-dipeptide supramolecular gelator (DMPV) is prepared, based on l -valine moieties having a pyridinyl group and a long fatty diamine. It is found that the gelator can immobilize organic/water binary mixed solvents, and gel-to-gel transitions with unprecedented opaque-to-transparent transformations are observed upon using aliphatic alcohols such as methanol, ethanol, 1-propyl alcohol, and isopropanol as the organic components. Morphological investigations indicate that a reassembly process occurs, and microstructure evolutions from agglomerates to nanofibers are observed. Opaque and transparent assemblies can interconvert, and respond and restore under mechanical force and pH stimuli. Moreover, Hansen and Flory–Huggins parameters are used to investigate the effect of the solvent on the gelation performance of DMPV. This may facilitate the structure and solvent optimizations and aid the development of advanced gel systems.