We will describe how nonequilibrium thermodynamics can help design methodologies for computing the properties of complex materials beyond equilibrium based on an efficient coupling of two different models: the non-equilibrium Molecular Dynamics (NEMD) method (playing the role of a micro-scale model) and a Monte Carlo (MC) method in an expanded ensemble being free of any long time scale constraints based on the use of a carefully selected set of conjugate variables. We will illustrate the method for the case of unentangled linear polymer melts, for which the appropriate structural variable to consider is the conformation tensor C whose corresponding thermodynamic conjugate variable is a tensorial field  a. We have been able to compute model-independent values for the tensor a, which for a wide range of strain rates (covering both the linear and the nonlinear regime) bring results for the overall polymer conformation from the two models on top of each other. By further computing the free energy of the deformed system through thermodynamic integration, we will show how one can check the validity of the fundamental Maxwell equations of equilibrium thermodynamics at conditions far beyond equilibrium (strong flow regime).