We apply a statistical-thermodynamic approach to the study of a particular physical system (two sets of nonlinearly coupled oscillators), driven far away from equilibrium. Such a system displays a kind of complex behavior consisting in the so-called Frohlich effect leading in steady-state conditions to a nonequilibrium phase condensation resembling the Bose-Einstein condensation of systems in equilibrium. A kind of "two-fluid model" arises: the "normal nonequilibrium phase" and Frohlich condensate or "nonequilibrium superphase," which is shown to be an attractor of the system. We work out some aspects of the irreversible thermodynamics of this dissipative complex system. Particular nonlinear properties are discussed and Lyapunov exponents determined. This kind of system gives a good modeling of polar vibration modes in polymers and biopolymers. (C) 2000 American Institute of Physics. [S0021-9606(00)50808-3].