Energy balance in dense microemulsions

• Published in: Journal of thermal analysis and calorimetry Vol. 92; no. 2; pp. 535 - 541
• Main Authors: Senatra, Donatella, Ziparo, C., Gambi, Cecilia M. C., Lanzi, L.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Dordrecht Springer Netherlands 01.05.2008; Springer
• Subjects: Analytical Chemistry; Chemistry; Chemistry and Materials Science; Colloidal state and disperse state; Emulsions. Microemulsions. Foams; Exact sciences and technology; General and physical chemistry; Inorganic Chemistry; Measurement Science and Instrumentation; Physical Chemistry; Polymer Sciences; Regular Papers; dense microemulsions; energy balance; percolation and bicontinuous transitions by DSC; Energy balance; Differential scanning calorimetry; Percolation; Thermal analysis; Microemulsion
• ISSN: 1388-6150; 1588-2926; 1572-8943
• DOI: 10.1007/s10973-007-8611-9

A water-in-oil microemulsion composed of water, AOT and decane with volume fraction φ=0.50 and molar ratio X =40.8 was analysed by DSC. The percolation and the bicontinuous transitions as well as the melting endotherms and the freezing exotherms were measured. The main attention was focussed on the system energy balance. It was found that, by freezing the samples after the occurrence of the percolative transition, the total heat released is significantly less than the heat absorbed in the melting endotherms. A simple geometrical model was used as an analysis tool of the aforementioned energy difference. Since the system studied exhibits a percolative transition of dynamic type, on approaching the percolation threshold temperature ( T ≤ T p ) and a static percolation for T ≥ T p , the structural change from the connecting water-droplet-cluster to a connecting water channel was schematised in the model as a change from a sphere-necklace to a water-cylindrical channel of equal volume and equal length. The surface energy associated with the formation of the two different geometrical surfaces was evaluated and the amount of saved energy compared with the experimentally measured one.