Mesoscale structure and fractal nature of 1-propanol aqueous solution: A reverse Monte Carlo analysis of small angle neutron scattering intensity

Mesoscale structures of salt-free and salt-added 1-propanol aqueous solutions have been analyzed by means of a reverse Monte Carlo (RMC) technique combined with small angle neutron scattering data. RMC analysis is carried out by using sub-million molecules and concentration-fluctuation is visualized. Effect of salt on the mesoscale structure is also visualized. Origin of fractal nature of the solution is attributed to the distribution of [gpp(r)−gpw(r)] and [gww(r)−gwp(r)]. 1-propanol-rich regions are surrounded by thin water-layers in the salt-free solution. The addition of salt shifts the thickness distributions of the water-layer to the larger value. However, the thickness distribution is scaled very well between the salt-free solution and the salt-added solution, suggesting a self-similarity of mesoscale structure of both solutions. Formation of concentration-fluctuation and salt-induced phase separation are discussed.