Estudo e determinação de diagramas de fase e propriedades físico-químicas em sistemas aquosos bifásicos (SABs) formados por PEG/L64 + sais de fosfato e em misturas binárias e ternárias baseadas em SABs

• Autor(a) principal: Faria, Diego Nunes
• Data de Publicação: 2015
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/7354
• topic: Phase diagrams; Dynamic viscosity; Density; Diagramas de fase; Viscosidade dinâmica; Massa específica; Química; Diagramas de fase; Viscosidade; Termodinâmica; Polímeros; 54

This work was divided into two parts. At first, the data of phase equilibrium of aqueous two-phase systems(ATPSs)formed by triblock copolymer L64 + potassium phosphate salts (pH 7 and 12) + water at different temperatures were studied; in the second one, it was carried the study and determination of the density and dynamic viscosity in binary and ternary mixtures inATPSs. First, the effect of temperature variation (5, 15 and 25 ° C) and the influence of pH on the position of the bimodal were studied. For both pH values studied, the rise in temperature caused an increase in biphasic area, featuring an endothermic process of phase separation. The rise in pH at a constant temperature provided an increase in the biphasic area, to regions where the formation of two phases occur at lower concentrations of copolymer and salt. Secondly, for ternary mixtures formed by PEG + salt + water, the viscosity at constant temperature decreased down to a certain mixture point and subsequently lifted, while PEG concentration was held constant. This may be associated with the process of formation of the two phases in ATPSs. For binary mixtures based on PEG + water, the dynamic viscosity increases with concentration and molecular weight and decreases with increasing temperature. For all blends, the density is practically independent of PEG’s molecular weight and as the temperature rises thedensity decreases. The physicochemical properties of the ATPSs were investigated and as the tie-line length(TLL) increased, the density and viscosity rose. As the ATPSs of PEG 3350g.mol-1possessed an exothermic phase separation process, the temperaturerise disfavored the formation of ATPS(aqueous two-phase system), thus increasing the physicochemical properties values once it demands larger quantities of components to segregate phases. The dynamic viscosity in the upper phases rose with increasing molecular weight, at both temperatures. The difference between ATPSs phases’ densities at 25 ° C increased with the decrease of molar mass. At 40 ° C, the ATPS formed by PEG 3350g.mol-1showed the greater differences in density due to the exothermic phase separation behavior.