Coagel Prepared from Aqueous Octyl β‐d‐Galactoside Solution

Abstract

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 b-D-galactoside (C 8 -b-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 C 8 -b-Gal concentrations below 30 wt% and a knee of the Krafft boundary exists around 2.5 wt% C 8 -b-Gal concentrations. The addition of NaCl increased T K slightly because of the salting-out effect. Powder X-ray diffraction (PXRD) analysis, fieldemission 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 C 8 -b-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 b-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.

Structural Characterization of Perpendicularly Aligned Submicrometer-Thick Synthetic Glycolipid Polycrystalline Films Using Conventional X-ray Diffraction

“…As shown in the figure, all of the surface regions consisted of polycrystalline species with sub-micrometric to micrometric scale lengths. In previous studies, the MOβGal tended to form fiber structures, not only in aqueous solutions, but also on solid surfaces when the solution was drop-casted on the Si substrate [29]. However, in this study, no fiber structure was discernible, indicating that the film consisted of rapidly formed polycrystallites without sufficient time to grow one-dimensionally on the substrate.…”

Effect of Freeze–Thaw Treatment on the Precipitation of Octyl <i>β</i>-D-Galactoside Hemihydrate Crystal from the Aqueous Solution

“…In a preliminary study, the addition of NaCl was confirmed to prolong the stability of the sol state of an Oct-Gal-water system at 4 . Although rapid precipitation within 1 min has been observed in the absence of NaCl 33 , it can be inhibited for at least 35 min in the presence of a 1.0 M NaCl aqueous solution under the same conditions. Such elongation of the induction period for the precipitation of the Oct-Gal crystal was expected to be crucial to prevent rapid precipitation during cooling.…”

“…Oct-Gal was prepared in a manner similar to the method reported previously by our group 33 and used after drying under vacuum at 60 for 2 h. Water and electrolytes purchased from Wako Pure Chemical Industries Ltd. were used as received. The sample solutions were prepared by the dissolution of prescribed amounts of Oct-Gal and electrolyte in water at a bath temperature of 50 .…”

“…tion, such a diffraction peak corresponding to the 010 plane was not clearly distinguished in a study previously reported for a 10 wt. Oct-Gal-water system 33 in the absence of an electrolyte. A space phase transition in the orthorhombic crystal systems was assumed to occur.…”

“…Our group has recently verified that the crystal-dispersed phase, or the so-called coagel, precipitates from an octyl β -D-galactoside Oct-Gal: Chart 1 -water system, leaving behind an aqueous micelle solution 33 . In this phase, the water-dispersed crystals comprising three-dimensional 3D fiber-like crystals covered a considerable amount of water.…”