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Encapsulation of N,N-diethyl-meta-toluamide and citronella oil via miniemulsion polymerization

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Author(s):
Guilherme Martinate Gomes
Total Authors: 1
Document type: Master's Dissertation
Press: Campinas, SP.
Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Química
Defense date:
Examining board members:
Liliane Maria Ferrareso Lona; Lucimara Gaziola de la Torre; Claudia Sayer
Advisor: Liliane Maria Ferrareso Lona
Abstract

Among all disease transmitting insects, mosquitoes represent the major threat since they can transmit maladies like malaria, yellow and dengue fever. Even though the main way of combating the spreading of these diseases is the control of the vectors population, the use of repellents is fundamental. Although some repellents can be used topically applied, its application is restricted and not recommended for babies. Moreover, the protection time of such repellents is limited to their fast evaporation. Therefore, the encapsulation of these substances and their use in the formulation of paints or in the impregnation of fabrics rise as a promising alternative. The encapsulation of substances can be achieved with a large number of techniques, but the miniemulsion polymerization is a simple technique which allows the formation of polymer particles with controlled dimensions and, under certain circumstances, encapsulate substances. The formulation of this technique requires a substance called costabilizer, which is responsible for the minimization of the diffusional degradation. There are many works in the literature that show the efficiency of costabilizers like hexadecane and vegetable oils, but until the present time, no works were found regarding the efficiency of N,N-diethyl-meta-toluamide (DEET) and citronella oil, which possess some characteristic properties, like high hydrophobicity, of good costabilizers. The use of such substances as costabilizers in the miniemulsion formulation would ensure not only the minimization of the Ostwald ripening, but would also grant an additional application due to their repellent activity. Thus, in the presented work, it was proposed the study of the encapsulation of DEET and citronella oil and the development of a thermo-responsive system suitable for the sustained release of these encapsulated actives. In the first stage of the presented work, a monomer composition, which would ensure the synthesis of a copolymer with a suitable glass transition temperature (Tg), was determined. Also, in this stage, the influence of this composition on the polymerization kinetics, polymer molar mass and polymer chain composition was evaluated. In the second stage of the work, it was studied the encapsulation of DEET and citronella oil and the influence of these substances on the polymerization kinetics, polymer molar mass, Tg, colloid stability and nanoparticle morphology. It was concluded that citronella oil is not an efficient costabilizer and that the structure of nanoparticles synthesized with DEET was of nanospheres or polymer matrices. It was also evidenced the thermal stability improvement of the entrapped DEET. In the third stage of the presented work, the release of DEET was studied. The polymeric films were able to sustain suitable DEET release rates for at least nine hours. The data regarding the release was fitted to two mathematic models and it was concluded that the mass transfer of DEET to the air occurs mainly by two distinct mechanisms: fickian diffusion and relaxational transport, which depend, among other aspects, on the Tg and the release temperature (AU)

FAPESP's process: 16/13427-0 - Encapsulation of N, N-dimethyl-meta-toluamide and citronella oil via miniemulsion polymerization
Grantee:Guilherme Martinate Gomes
Support type: Scholarships in Brazil - Master