Abstract: A method of constructing a model of permeation to mixtures of solvents of a multilayer polymer structure with n monolayers and its associated computer program. For example, selecting several initial compositions of solvent mixture E1 to Ey, carrying out a sorption measurement and a measurement of diffusion, discretizing said multilayer structure in space and time, estimating partial fluxes of each of the compounds of said composition of solvent mixture between each elementary slice of said multilayer structure, estimating on the one hand a maximal sorption ceiling of said downstream monolayer B and on the other hand the composition of solvent mixture at inlet of said downstream monolayer B, performing a mass balance from slice to slice as a function of time, adjusting the profile of concentrations, storing the concentration profiles and the partial fluxes obtained.