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| Author(s): |
Lucas Urbano Jose
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2021-09-15 |
| Examining board members: |
Vera Regina Leopoldo Constantino;
Gustavo Frigi Perotti;
Ana Paula Ramos
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| Advisor: | Vera Regina Leopoldo Constantino |
| Abstract | |
Pickering emulsions are emulsion in which the stabilizer is a solid-state particle instead of a surfactant. Colloidal size particles are good candidates to this goal, once a better particle layer around the dispersed phase droplet may be achieved and therefore higher stability to the system as a whole. This work pursues to understand how layered double hydroxides (LDH) with both inorganic (chloride) and organic (apocarothenoids) interlayer anions may act as Pickering emulsifiers. Intercalation with the pH-constant coprecipitation method of bixin and norbixin (two natural occurring anatto derivative apocarothenoids) was studied. Such species were commercially obtained, purified and characterized before the intercalation. X-ray diffraction measurements on the organically-modified LDH attested the intercalation of both anions and vibrational spectroscopy (infrared and Raman) assured that their structures were maintained. As small-sized LDH particles were a requirement, fast coprecipitation method was studied. The norbixin-intercalated LDH (LDH_NBxn) was chosen as the Pickering emulsifier, while chloride-intercalated LDH (LDH_Cl) would be helpful to the understanding of the anionic role on the emulsion. The LDH particles prepared in the presence and absence of the organic anion showed different results. The emulsions prepared with LDH_NBxn showed high stability and gel behavior in all concentrations used, while those prepared with LDH_Cl showed similar behavior only on the highest concentration. This behavior was characterized with oscillatory rheology measurements and the parameters that described the solidstate characteristic and its resistance were dependent on the dispersion concentration, the ion present on the LDH and the amount of oil phase used. Solid particles acting as bridges between two different dispersed-phase droplets may be responsible for the gel behavior, as a tridimensional array of droplets may be formed, as attested by confocal microscopic measurements. The inorganic layer plays a key role on the emulsions final property, since emulsions prepared with only norbixinate did not show similar gel behavior. Considering the biocompatibility of the LDH material alongside to the properties of norbixin, the emulsions prepared here deserve further investigation regarding its application on cosmetics and pharmaceutical industry. (AU) | |
| FAPESP's process: | 19/10002-7 - Utilization of layered compounds for intercalation and encapsulation of natural Apocarotenoids |
| Grantee: | Lucas Urbano José |
| Support Opportunities: | Scholarships in Brazil - Master |