Interaction between amphiphiles and water molecules in concentrated bilayer aqueous colloids

Abstract

Interaction between amphiphiles and water molecules in micelle or bilayer structure has been investigated using aqueous colloids of various amphiphiles through the rheological data and the spin-lattice relaxation time T 1 of the proton of water molecule. T1 of the water proton has been measured by the inversion recovery method and determined as a single exponential relaxation process.The chemical shift of the water proton is almost independent of the amphiphilic concentration; however, it shifts toward a higher magnetic field with increasing temperature in a way similar to that in pure water and in the amphiphilic aqueous systems. These facts mean that there is no significant difference in the magnetic field environment of the water protons in these systems.The water molecule is not necessarily bound in the fully developed micelle or bilayer (rod-like or lamella) structure which induces the high viscosity or high rigidity of the colloidal system. On the other hand, the water molecule is bound in the micelle colloids of amphoteric amphiphiles or amphiphiles whose molecular assembly creates a relatively strong electrostatic field. The activation entropy of the bound water is negative and this suggests that water molecules assume some ordered structure in the bound state.

Micelle structure in isotropic aqueous colloids of a poly(oxyethylene) amphiphile C12E8

“…On the other hand, the temperature dependence of T1 for the aqueous colloids shows a discontinuous change in the range of 40-50 ~ It has been considered that T1-1 corresponds to the correlation time re of molecular motion of the water molecule. The increase in T1 (the decrease in Vc) of the proton of pure water with temperature means that the motion of the water molecule becomes activve by the dissociation of water-water hydrogen bonds with increasing temperature [22,23]. In the aqueous colloids, the values of T1 above the discontinuous temperature range are almost equal to that of pure water, especially in 10 and 20 wt % systems.…”