Coagel Prepared from Aqueous Octyl β -d-Galactoside Solution

Structuring of semi-crystalline networks in water systems is significant for a variety of industrial applications. In the present work, we investigated the coagel formation from aqueous octyl β-d-galactoside (C₈-β-Gal) solutions and characterized the crystal structure and crystallite network in the prepared coagel. Differential scanning calorimetry (DSC) confirmed that the Krafft boundary temperature (T_K) is 32–35 °C for C₈-β-Gal concentrations below 30 wt% and a knee of the Krafft boundary exists around 2.5 wt% C₈-β-Gal concentrations. The addition of NaCl increased T_K slightly because of the salting-out effect. Powder X-ray diffraction (PXRD) analysis, field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) observations revealed that the coagel is comprised of the three dimensional bundled semi-crystalline network consisting of a “ribbon crystal phase” of hemihydrate crystals. Moreover, the excellent ability of C₈-β-Gal to form a macroscopically homogeneous coagel was demonstrated by the comparison with other representative mono-alkylated glycoside’ systems containing octyl a-d-glucoside or dodecyl β-d-glucoside. Persistence of the liquid phase without liquid–liquid phase separation prior to and during the coagel formation was a key factor for the preparation. A novel coagel was obtained from a principal synthetic galactoside.