A phenomenological approach for the chemo-responsive shape memory effect in amorphous polymers

In this work, we present a phenomenological approach to study the state transition and working mechanism of the chemo-responsive shape memory effect (SME) in shape memory polymers (SMPs). The thermodynamics of polymer solution and free-energy theory are initially applied to quantitatively identify the factors that trigger a chemo-responsive SME. After this, a field theory is developed to couple the chemical potential, stress and relaxation time in a polymer system with free-energy functions. Furthermore, by means of combining together and utilizing the Gordon-Taylor (GT) theory and Free-Volume (FV) theory, the intrinsic plasticizing effect and generalized plasticizing effect are decoupled and quantitatively determined as the driving forces for the chemo-responsive SME in SMPs. In addition, the influence of the intrinsic plasticizing effect and generalized plasticizing effect on the glass transition temperature (T-g) is consequently numerically modeled using the GT and FV equations, respectively. Finally, the theoretical model is verified by the available experimental data reported in the literature and then compared with the simulation results of a semi-empirical model. This phenomenological approach is expected to provide a powerful simulation tool for extracting the transition temperature parameter, theoretical prediction and experimental substantiation of the response of chemo-responsive SME in amorphous SMPs.