  Stimuli-responsive macromolecules display large conformational changes during
their dynamics, sometimes switching states, and are an integral property for
the development of soft functional materials. Here, we introduce a mean-field
dynamical density functional theory (DDFT) for a model of responsive colloids
(RCs) to study the nonequilibrium dynamics of a colloidal dispersion in
time-dependent external fields, with a focus on the coupling of translational
and conformational dynamics during their relaxation. Specifically, we consider
soft Gaussian particles with a bimodal size distribution between two confining
walls with time-dependent (switching-on and off) external gravitational and
osmotic fields. We find a rich relaxation behavior of the systems in excellent
agreement with particle-based Brownian dynamics (BD) computer simulations. In
particular, we find time-asymmetric relaxations of integrated observables (wall
pressures, mean size, liquid center-of-mass) for activation/deactivation of
external potentials, respectively, which are tuneable by the ratio of
translational and conformational diffusion time scales. Our work paves thus the
way for studying the nonequilibrium relaxation dynamics of complex soft matter
with multiple degrees of freedom and hierarchical relaxations.
