This paper reports a study of the supramolecular self-assembly process of low molecular mass organic gelators in the formation of nanofiber networks. Methyl 4,6-O-benzylidene-α-D-glucopyranoside derivative compounds were designed to investigate the effect of substituents on the molecules' self-assembly properties. Gelators were prepared using two different substituent groups at position 4 of the aromatic ring: an electron-donating series (with n-alkoxyl groups) and an electron-withdrawing series (with n-alkoxycarbonyl groups), where n = 2, 3, 4, 8 and 16 C atoms. The gelation process in several gelator concentrations was studied in polar and apolar organic solvents. Differential scanning calorimetry revealed that the gelation temperature increases with the molar concentration and decreases with alkyl chain size in both series of gelators. Scanning electron microscopy images of the xerogel showed cylindrical aggregates. In situ small-angle X-ray scattering analysis corroborated a model of self-assembly based on one-dimensional nanofiber growth in a two-phase gel system, while X-ray powder diffraction revealed partial crystallization for the gelator compounds and for some gel samples. The infrared analyses of gels indicated that molecules undergo a self-assembly process via hydrogen bonding, suggesting that both OH groups are involved for samples of the n-alkoxycarbonyl series. On the other hand, the n-alkoxyl series aggregation process depends on the size of the alkyl chain. The compound with the smallest group, n-propoxyl, also undergoes self-assembly using both OH groups. Conversely, the rest of the n-alkoxyl series uses only one hydroxyl group.
Self-assembly of block copolymers during hollow fiber spinning: an in situ small-angle X-ray scattering study
