科研之友
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摘要
Four different surface fractal dimensions (D-sf's) of anisotropic silica (SiO2-x) similar in size were synthesized by layer-by-layer molecular imprinting strategy. Grafting was confirmed by FT-IR and X-ray photoelectron spectroscopy. The surface and interfacial properties of particles were confirmed by transmission electron microscopy, nitrogen adsorption, dynamic light scattering, and contact angle measurement. Results showed that D-sf's of SiO2-1, SiO2-2, SiO2-4, and SiO2-6, were 2.47, 2.55, 2.62, and 2.56, respectively. Moreover, the modified silica shape varied from spherical to anisotropic particle, and particle hydrophobicity decreased with increased the D-sf.. Stable emulsions were prepared by these particles. The effects of particle concentration, hydrophobicity, and D-sf on the formation, stability, and rheology of emulsions were investigated using an optical microscopy and rheometer. Optical microscopy images showed that unmodified silica failed to form stabilized emulsions due to excellent hydrophility, and particles with D-sf = 2.62 and 0.2 wt% concentration were the best for stabilized emulsions. Moreover, increased D-sf led to decreased droplets size smaller and easier network formation. Rheology measurement further showed that increased 1351 led to increased viscoelasticity and thermal stability of emulsions due to the formation of rigid volume-filling networks. This finding indicated that the particle fractal structure strongly affected the structures in the suspension to immobilize the emulsion droplets in these networks. Emulsion also exhibited longer lambda-cyhalothrin release speed with increasing D-sf using lambda-cyhalothrin as model hydrophobic drug. The lambda-cyhalothrin release kinetics well-fitted the Weibull model.
