Microcalorimetric Studies on the CMC and Thermodynamic Functions of a Nonionic Surfactant (Tween80) in DMF/Long-Chain Alcohol Systems from T=298.15 to T=313.15 K

The power-time curves of the micelle formation process were determined for the nonionic surfactant Tween80/nonaqueous solvent (DMF)/long-chain alcohol (n-heptanol, n-octanol, n-nonanol, and n-decanol) systems by titration microcalorimetry at temperatures of (298.15, 303.15, 308.15, and 313.15) K. From the power-time curves, the CMC and DH_m^upthetaDelta H_{mathrm{m}}^{uptheta} values were obtained. The corresponding values of DG_m^upthetaDelta G_{mathrm{m}}^{uptheta} and DS_m^upthetaDelta S_{mathrm{m}}^{uptheta} were also calculated. The relationships of the CMC with the carbon number of the alcohol, the concentration of alcohol, and the temperature, along with the thermodynamic functions, are discussed.