We study the influence of monomer chemistry and sequence on the properties of charged polymers in solution and at interfaces to design stimuli-responsive materials for applications ranging from separations to tissue engineering.

• Polyelectrolyte Brushes (PEBs): We explore how to modulate transport processes in PEBs for purification, recovery, and sensing applications using monomer chemistry, pH, and salt as critical control parameters. PEBs consist of charged polymers end-tethered to solid supports and constitute a powerful route to modifying the interfacial properties of multicomponent materials. Controlling the interfacial response requires understanding how structural and environmental parameters influence brush conformation. We use surface initiated polymerization, light scattering, and advanced fluorescent microscopy techniques to uncover the physics of these systems.

• Polyampholyte Solutions: Inspired by the assembly of intrinsically disordered proteins (IDPs) into condensed states (i.e., liquid-like droplets and solid-like amyloids), we produce polyampholytes that mimic IDPs to explore the influence of factors such as monomer sequence and chirality on chain conformation, mesoscale assembly, and phase behavior. PAs are charged polymers that contain cationic and anionic monomers along their polymer backbone.  Improved understanding and control over the complex intra- and interchain interactions has enormous potential for designing PA-based stimuli-responsive materials. We use solid-phase synthesis, light scattering, and rheological characterization to better understand the mechanisms that control polyampholyte phase behavior.

• Structured Fluid-Fluid Interfaces: We apply our expertise in charged polymers to design surface-active and stimuli-responsive molecules that modify the mechanical properties of fluid-fluid interfaces commonly found in multiphase systems (e.g., personal care products, wastewater treatment, oil recovery). We are particularly interested in designing sustainable solutions to disrupt and/or break the asphaltene-stabilized water-in-oil (W/O) emulsions that form during crude oil production by weakening their interfacial mechanical properties. To advance the design of demulsifiers, it is necessary to connect asphaltene structure to interfacial activity, mechanical strength, and ultimately emulsion stability. More broadly, this understanding will be applied to advance other fields where structured interfaces are ubiquitous, including pharmaceuticals, cosmetics, and food production. We use interfacial rheology and light scattering to better understand the mechanics at interfaces.