Formação e caracterização de micelas reversas de (EO)13(PO)30(EO)13 em P-XILENO

• Autor(a) principal: Gomes, Deizilene de Souza Barbosa
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4231
• topic: Micelas reversas; Colóides; Pontos quânticos; Reverse micelles; Colloids; Quantum dots; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA::FISICA DA MATERIA CONDENSADA

Amphiphilic molecules have an intrinsic characteristic to form self-organized structures when dissolved in a solvent that is compatible sith to one of their components. The macromolecule of the triblock copolymer used in this work (Pluronic L64, (EO)13(PO)30 (EO)13) possesses a structure consisting of two hydrophilic regions, of poly (ethylene oxide)-PEO, and another hydrophobic part, of poly (propilene oxide) PPO, and, when dissolved in organic solvents forms reverse micelles above of a certain concentration (Critical Micellar Concentration-CMC) when are small amounts of water added. These aggregates consist of a core formed by PEO chains solvated with water molecules surrounded by a PPO shell. The diagram of water solubility in the L64-p-xylene binary system shows that the CMC is ≈ 12% m/m. With dynamic and static light scattering (DLS/SLS) measurements, its was possible to determine the hydrodynamical radius (Rh) of micelles (~ 7 nm) with repulsive interactions. With SAXS it was observed that the L64 chains have repulsive interactions and their (RG) size is around 1.6 nm. All techniques show that the micellization occurs only in the presence of water. The reverse micelles formation is a entropically favored exothermic process (ΔS>0), as supported by isothermal titration calorimetry (ITC).