Abstract
Dynamical polydispersity in single-particle properties, for example a fluctuating particle size, shape, charge density, etc, is intrinsic to responsive colloids (RCs), such as biomacromolecules or microgels, but is typically not resolved in coarse-grained mesoscale simulations. Here, we present Brownian dynamics simulations of suspensions of RCs modeling soft hydrogel colloids, for which the size of the individual particles is an explicitly resolved (Gaussian) degree of freedom and dynamically responds to the local interacting environment. We calculate the liquid structure, emergent size distributions, long-time diffusion, and property (size) relaxation kinetics for a wide range of densities and intrinsic property relaxation times in the canonical ensemble. Comparison to interesting reference cases, such as conventional polydisperse suspensions with a frozen parent distribution, or conventional monodisperse systems interacting with an effective pair potential for one fixed size, shows a significant spread in the structure and dynamics. The differences, most apparent in the high density regimes, are due to many-body correlations and the dynamical coupling between property and translation in RC systems, not explicitly accounted for in the conventional treatments. In particular, the translational diffusion in the RC systems is surprisingly close to the free (single RC) diffusion, mainly due to a cancellation of crowding and size compression effects. We show that an effective monodisperse pair potential can be constructed that describes the many-body correlations reasonably well by convoluting the RC pair potential with the density-dependent emergent size distributions and using a mean effective diffusion constant.
Highlights
Responsive colloids (RCs) [1,2,3,4,5,6,7] and related responsive materials [8,9,10,11] have drawn a lot of attention in the physical sciences
The responsive colloids (RCs) respond to increased crowding by contracting in size. (This will not happen in the canonical conventional polydisperse (CP) system where p(σ) remains frozen.) This phenomenon is well known in the literature for microgels, where the swelling ratio of microgels has been observed to decrease with density, see, e.g., reference [62]
We conclude that on the structural level the RC model gives rise to many body correlations which are very different than the conventional conventional monodisperse (CMp) model, but can be approximately captured by a monodisperse model such as CMN, when the emergent distributions are known
Summary
Responsive colloids (RCs) [1,2,3,4,5,6,7] and related responsive materials [8,9,10,11] have drawn a lot of attention in the physical sciences. Large responsiveness is a feature displayed, for example, by solvated polymers that have broad and often polymodal conformational distributions. The class of thermosensitive polymers (including biomolecules) typically displays a critical solution temperature (CST) at which the polymers relatively sharply switch between two different physicochemical states. The properties of a RC, made, for example, from a thermosensitive hydrogel, changes substantially at the CST: size changes by a factor of two or three are very typical [6, 7]. The broad conformational and responsive distributions of polymers can be harvested for tailoring functionality in applications, for instance, actuators, soft sensors, triggered drug release by nano-carriers [12, 16], or selective catalysis in polymeric nanoreactor particles [17, 18]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
