Study On Microstructure And Phase Stability Of Nanometer Emulsion

A homogenouse nano-emulsion was prepared via high-energy dispertion method with sodium dodecyl sulfate (SDS) and betaine as surfactant system, cool wintermint as flavor oil. The microstructure of the nano-emulsion was characterized with multi-scale imaging and microscopy tools, e.g. polarized light microscopy, cryogenic scanning electron microscopy (cryo-SEM), cryogenic transmition electron microscopy (cryo-TEM). Combining with other techniques, e.g. differential scanning calorimetry (DSC) for the water bounding status evaluation in nano-emulsion system, synchrotron small angle X-ray scaterring (Synchrotron SAXS) for the surfactant crystallization in the nano-emulsion system, Rheology methods for the rheological properties of polymer systems, the impacts from salts, solvents and polymers on the microstructure and phase stability of nano-emulsion system were investigated. Addtionaly, the possible mechanism was discussed. The thesis is composed with below three main parts.Firstly, by utilizaing multi-scale imaging and microscopy tools, the microstructure of the nano-emulsions was confirmed as multi-layered vesical with size ranged from50nm to300nm. The dynamic change of the microstructure and phase stability of the nano-emulsion system was studied. Additionally, the impact from emulsification time, the volume fraction of the emulsion, co-surfactant and different salts systems on the microstrucute and phase stability of nano-emulsion were studied. It was found that increase the emulsification energy or adding1%betaine could improve the phase stability in a certain level. And increasing the volume fraction of nano-emulsions to40%or60%could significantly improve the phase stability up to4months. As for the impact from salts, it was found that divalent zinc ion could obviously improve the phase stability and the diameter of the nano-emulsion was positively correlated with the conductivity.Secondly, via DSC, the water bounding status impacted by sorbitol was studied and it was found that60%sorbitol could effectively bond the water. According to the microstructure study via cryo-SEM and cryo-TEM, it was found addint60%sorbitol could change the relative stable microstructure from worm-like micelle to relative unstable multi-layered vesicle. As for the other solvent polyethylene glycol (PEG), Synchrotron SAXS was leveraged to understand its impact on surfactant soluability. PEG600could more effectively increase the soluability. Additionally, via cryo-SEM, the microstructure fromed by2%PEG300could most effectively improve the stability of the nano-emulsion system.Thirdly, the rheology profiles of four different polymers (CMC, Xanthan gum, Carbomer, HEC) were studied within the high sorbitol system. Combining with cryo-SEM, the polymer’s impact on microstructure and phase stability of the nano-emulsions were investigated and the possible mechanisms were discussed. It was found that the anionic polymer could induce the flocculation of the emulsion droplets. With lower polymer level (e.g.0.2%CMC), the phase separation was accelerated, while higher polymer level (e.g.0.7%CMC) could significantly improve the phase stability up to4months.Since the salts system, the solvent systems and polymers studied in this thesis are frequently used in daily-use chemistry industry or cosmetics, this work is very meaningful to guide the pratical application.