The extent of nonequilibrium dictates the activation energy for relaxation of molecular recoiling stress in dewetting thin polymer films

Spin-coated polymer films are trapped in nonequilibrium polymer chain conformations, resulting in an inherent drive to attain equilibrium, the molecular recoiling stress. We investigate the relaxation of molecular recoiling stress in thin polymer films and find a stress dependence in activation energy. As the films evolve from initial nonequilibrium toward equilibrium, the activation energy for stress relaxation follows an enthalpy–entropy compensation (EEC) relation characteristic of the slow Arrhenius process (SAP). Analysis via the collective small-displacement (CSD) model reveals that films farther from equilibrium exhibit higher activation energies, consistent with greater residual stress engaging a larger number of cooperative segmental units during relaxation. These results establish the presence of nonequilibrium dependence of activation energy and a SAP-type dynamics as a governing mechanism for molecular recoiling stress relaxation.