Controlled Transport and Assembly of Soft Complex Matter

• Applicant: Professor Dr. Arash Nikoubashman
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics ; Experimental and Theoretical Physics of Polymers ; Synthesis and Properties of Functional Materials ; Fluid Mechanics
• Term: from 2015 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 274340645

This proposal focuses on the directed assembly of colloid-polymer mixtures in and out of equilibrium, systems that play a significant role for many scientific and industrial applications. For example, polymers are routinely added in low concentrations to manipulate colloidal suspensions, while solid nanoparticles are often used as fillers to enhance the properties of dense polymer melts and glasses. The proposed research plan is divided into two work packages (WPs), which focus on the structure and rheology of amphiphilic polymer-colloid mixtures (WP1), and on the packaging and transport in polymer-grafted nanoparticle (GNP) systems (WP2).WP1: Over the past decades, extensive research was conducted to understand the equilibrium and flow properties of binary colloid-polymer mixtures under good solvent conditions, where the interactions are purely repulsive and the physical behavior is dominated by entropic effects. However, many real systems have a slight mismatch in solvent quality for the two species, which is already sufficient to cause a sizable attraction between the colloids and polymers. This situation is considerably more involved compared to the athermal limit, because the colloids and/or polymers can form (reversible) aggregates. To better understand these complex systems, we plan to simulate mixtures of amphiphilic Janus spheres and either hydrophobic or amphiphilic polymers at rest and under shear. The addition of adsorbing polymers could dramatically influence the self-assembled structures and the response to shear, as the polymers are able to form bridges between the individual particles and thus delay the shear-induced cluster breakup. WP2: Another intriguing manifestation of colloid-polymer mixtures are GNPs, where soft (organic) macromolecules are attached to the surface of rigid (inorganic) NPs. These effectively one-component hybrid materials allow for improved material properties compared to conventional bulk polymers or traditional nanocomposites. The macroscopic response characteristics of the bulk materials strongly depend on the microstructural features of the GNPs. Thus, we plan to develop theoretical models and perform simulations to better understand how the size, shape, and interpenetration of the polymer coronas depend on the microscopic GNP properties such as grafting density and graft length. Further, we will study the transport of free polymers and/or small molecules through the polymer matrix of the brush particle assemblies.

• DFG Programme: Independent Junior Research Groups