arXiv subjects

Giuseppe Briganti

Publications and source records attributed to Giuseppe Briganti.

2 recordsLinked to original sources

arXiv2006

Shear and longitudinal viscosity of non-ionic C12E8 aqueous solutions

We present measurements of the steady shear viscosity, the longitudinal elastic modulus and the ultrasonic absorption in the one-phase isotropic liquid region of the nonionic surfactant C12E8 aqueous solutions. The overall results support the presence of two separated intervals of concentration corresponding to different structural properties. In the surfactant-rich region the temperature dependence of the steady shear viscosity follows an equation characteristic of glass-like systems. The ultrasonic absorption spectra show unambiguous evidence of viscoelastic behaviour described by a Cole-Cole relaxation formula. In the water-rich region the behaviour of the measured quantities are more complex and reflect the presence of dispersed aggregates whose size increases with temperature and concentration. An additional low frequency contribution is also observed, which is ascribed to the exchange of water molecules and/or surfactant monomers between the aggregates and the bulk solvent region.

cond-mat.soft↗

arXiv1998

Interfacial properties of nonionic micellar agregates as a function of temperatures and concentrations

By means of density, dielectric spectroscopy and sound velocity measurements we perform a systematic study on the polyoxyethylene $C_{12}E_{6}$ nonionic surfactant solutions as a function of temperature and concentration. Both density and sound velocity data, at about $34^{\circ}C$, coincide with the value obtained for pure water. Above this temperature the density is lower than the water density whereas below it is greater, the opposite happens for the compressibility. Combining results from these different techniques we tempt a very detailed description of the evolution of the micellar interfacial properties with temperature. It is well known that nonionic surfactant solutions dehydrate, growing temperature. Our results indicate that this process is associated with a continuous change in the polymer conformation and in the local density of the micellar interface.

physics.chem-ph↗