Stimuli-responsive polymers, or smart polymers, are capable of conformational or chemical changes responding to external stimulus, such as temperature, pH, light, electric or magnetic field. By grafting stimuli responsive polymer brushes to various substrates with well controlled density, a responsive surface coating with reversible physicochemical properties, such as friction and wettability, can be fabricated. In membrane systems, responsive coatings have been reported to be able to mitigate organic and biological fouling. However, how the dynamic structural changes affect particle attachment and detachment are not well understood. This study aims to investigate the attachment and detachment behavior of particles with different size on various responsive polymer brush coatings, and elucidate the specific impact of particle size and polymer brush thickness and grafting density.<br/>Thermo-responsive poly(N-Isopropylacrylamide) (PNIPAM) polymer brush coatings were formed on glass substrates using activators regenerated by electron transfer for atom transfer radical polymerization (ARGET-ATRP). By changing the polymerization time and the initiator concentration, the thickness and the grafting density of the PNIPAM polymer brushes can be adjusted. The polymer brush coatings are thoroughly characterized by X-ray photoelectron spectroscopy, atomic force microscopy, captive bubble contact angle measurement and the quartz crystal microbalance with dissipation (QCM-D) technique. From QCM-D result, the synthesized PNIPAM polymer brush coating underwent stable and reversible structural change from swelling to collapsed status when the temperature increased over 33°C in pure water.<br/>The adhesion and detachment of model polystyrene particles of diameters ranging from 0.2 um to 6 um are systematically studied on PNIPAM coatings of varied grafting density, polymer length, and end functional groups. Measurements are performed with or without temperature transition. Primary results showed that particle attachment and detachment on these polymer brush coatings strongly depended on the interplay of polymer brush density and particle size. The findings provide important guidelines for the design of polymer brush coatings for applications including fouling and scaling control.

Particle adhesion and detachment on thermo-responsive polymer brush coatings: Interplay of grafting density and particle size

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.