Properties of aqueous solutions of nonionic surfactants, Triton X-114 and Tween 80, at temperatures from 293 to 318 K: Spectroscopic and ultrasonic studies

- Hydration of surfactant molecules influences on CMC.
- Values of the hydration number decrease at concentrations higher than CMC.
- The longer the amphiphile, the lower compressibilities.
- Water and Tween 80 molecules can be not completely mixed in solution.

The speed of sound, density and refractive index of aqueous solutions of the nonionic surfactants, p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethyleneglycol) Triton X-114 (TX114) and polysorbate 80, Tween 80, have been measured over the entire range of concentration at 293, 298, 303, 308, 313 and 318 K under atmospheric pressure. Steady state fluorescence measurements have been also made using pyrene as a probe. From the experimental data the quantities such as critical micelle concentration (CMC), apparent dielectric constant, hydration number, isentropic compressibility, apparent specific adiabatic compressibility of a solute, intermolecular free length, acoustic impedance and molar sound number were determined. The variation of these parameters with concentration and temperature was discussed in terms of intermolecular interactions in the solution of a given surfactant.

Values of the intermolecular free length of the nonionic surfactants, TX114 and Tween 80, vs. temperature.129