Exploiting the paradoxical effect of surface roughness on the interfacial pinning of colloids to engineer stimuli responsive emulsions

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

Efficient remediation strategies to capture and remove forever chemicals such as polyfluoroalkyl substances (PFAS) are crucial to mitigate their detrimental health and environmental impacts. However, current technologies are ineffective- strategies degrading PFAS often lead to still-toxic intermediates, and membrane technologies have poor efficiency. In this project, a potential solution to remove PFAS from wastewater will be pursued. Since PFAS molecules are negatively charged and concentrate at oil-water interfaces, particles will be specifically engineered to pin to the interface between oil and water, adsorb PFAS due to opposite charge interactions, and be removed from the interface to isolate PFAS and recycle the particles. This project will advance the fundamental science of utilizing rationally engineered particles for interfacial materials processing, with the long term goal of helping society via environmental remediation strategies. In addition, educational and outreach activities are integrated into this project, including the development of active learning workshops for middle and high school students to expand awareness of the chemistry and impacts of PFAS molecules on the environment and how engineering solutions involving multiphase materials are being pursued. The proposed project will investigate how particle surface roughness dictates the capillary pinning and interfacial mechanics of spherical and ellipsoidal polymer microparticles. This work is motivated by the potential to use colloids pinned to fluid interfaces to adsorb environmental pollutants, namely PFAS, de-pin from the interface, and successfully be sequestered. However, the behavior of rough particles, which afford increased surface area for adsorption and tunable pinning energetics, at fluid interfaces is poorly understood. The central hypothesis is that adsorption of PFAS molecules will alter the interfacial contact angle of pinned microparticles, causing emulsions to destabilize once sufficient molecules are adsorbed. To realize this vision, novel synthetic techniques to control the roughness and chemistry of polymer spheres and ellipsoids will be applied such that tunable interactions with PFAS molecules are achieved. Mirau interferometry will quantify, in situ, the resultant interfacial pinning, which will be related to corresponding experiments examining the interfacial monolayer viscoelasticity. By linking particle characteristics (size, shape, chemistry, roughness) with interfacial properties, we will be able to identify design principles for engineering emulsions with selective response to environmental stimuli. This work will provide fundamental understanding of how manipulating interfacial pinning via colloidal roughness dictates the interfacial mechanics of particulate monolayers. By accomplishing these aims, a scalable and versatile strategy to use colloidal particles to perform environmental remediation will be established. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.