Dibutyl phosphate/propylamine mixtures show supra-molecular slow building up under magnetic field

Abstract

Liquids with anisotropic local nanostructures which are able to be oriented by a magnetic field can give birefringence. Usually magnetically-induced birefringence is low owing to the low magnetic energy of molecules and to the averaging effect due to thermal agitation. At the same time, the response is usually very fast given the typical timescales of molecular orientational dynamics (nanoseconds). However, we show that the dibutyl phosphate/propylamine liquid mixture is characterized by an extremely slow response (hours) to the magnetic field and by an intense overall effect (Δn/λ ≈ -0.1m^(-1) at 1 Tesla). This surprising behavior has been interpreted as a manifestation of a novel phenomenon of progressive building up of larger and larger internally ordered hetero-associates driven by the magnetic field and involving strongly interacting amphiphiles.