The liquid crystalline phase behavior and sol-gel transition in halloysite nanotubes (HNTs) aqueous dispersions have been investigated by applying polarized optical microscopy (POM), macroscopic observation, rheometer, small-angle X-ray scattering, scanning electron microscopy, and transmission electron microscopy. The liquid crystalline phase starts to form at the HNT concentration of 1 wt %, and a full liquid crystalline phase forms at the HNT concentration of 25 wt % as observed by POM and macroscopic observation. Rheological measurements indicate a typical shear flow behavior for the HNT aqueous dispersions with concentrations above 20 wt % and further confirm that the sol-gel transition occurs at the HNT concentration of 37 wt %. Furthermore, the HNT aqueous dispersions exhibit pH-induced gelation with more intense birefringence when hydrochloric acid (HCl) is added. The above findings shed light on the phase behaviors of diversely topological HNTs and lay the foundation for fabrication of the long-range ordered nano-objects.
We have reported a novel procedure to prepare 3,5-dihydroxy-4-isopropylstilbene (DHPS) nanoemulsion, using a low-energy emulsification method. Based on the phase diagram, the optimum prescription of nanoemulsion preparation was screened. With polyoxyethylenated castor oil (EL-40) as the surfactant, ethanol as the co-surfactant, and isopropyl myristate (IPM) as the oil phase, the DHPS nanoemulsion was obtained with a transparent appearance, little viscosity, and spherically uniform distribution verified by transmission electron microscopy and laser scattering analyzer. The nanoemulsion was also determined by FT-Raman spectroscopy. The DHPS nanoemulsion demonstrated good stability and stable physical and chemical properties. The nanoemulsion dramatically improved the transdermal release of DHPS (from 8.02 ?g · cm(-2) to 273.15 ?g · cm(-2)) and could become a favorable new dosage form for DHPS.
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