The interfacial tension γ of a hexane solution of 1,1,2,2-tetrahydroheptadecafluorodecanol CF3(CF2)7(CH2)2-OH (FC10OH) against water was measured as a function of temperature T and molality m1 under atmospheric pressure. By the calculation of the interfacial density ΓH1 and then drawing the interfacial pressure π area per adsorbed molecule A curves, it was concluded that two types of first-order phase transitions take place from the gaseous to the expanded state and from the expanded to the condensed one in the adsorbed film of FC10OH. The partial molar entropy s̄H1 - sO1 and energy changes ūH1 - uO1 associated with the adsorption were estimated and compared with those of 1,1,2,2-tetrahydrohenicosafluorododecanol CF3(CF2)9(CH2)2OH (FC12OH). It was found that these values of FC10OH are negative and larger than those of FC12OH. It was suggested that, although both s̄H1 and sO1 values increase, the increment in s̄H1 is larger than that in s̄H1 when the fluorocarbon chain is lengthened from FC10OH to FC12OH. Furthermore, it was realized that the energetical stabilization of the FC10OH molecule accompanied by adsorption is less than that of the FC12OH molecule. Furthermore, it was shown that the temperature and pressure dependencies of the π vs A curve are related to the partial molar entropy and volume changes of adsorption, respectively. By estimation of the temperature and pressure coefficients of A at constant π, it is found that a temperature increase of only 1 K is sufficient to keep π and A constant upon a decrease of the pressure by 1 MPa.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry