Tuning Gold Nanoparticle-Poly(2-hydroxyethyl methacrylate) Brush Interactions: From Reversible Swelling to Capture and Release

Tailoring the interaction between surfaces and nanoparticles (NPs) affords great opportunities for a range of applications, including sensors, information storage, medical diagnostics, and filtration membranes. In addition to controlling local ordering and microscale patterning of the NPs, manipulating the temporal factors determining the strength of the interaction between NP and surface enables dynamic modulation of these structural characteristics. In this contribution we demonstrate robust polymer brush-NP hybrids that exhibit both reversible swelling and reversible NP adsorption/desorption. Polymer brush functionality is tailored through post-functionalization of poly(2-hydroxyethyl methacrylate) (PHEMA) brushes on flat solid substrates with alpha-amine conjugates ranging from perfluoro alkanes to poly(ethylene glycol) of varying molecular weights. The type of functionality controls NP affinity for the surfaces. In the case of poly(ethylene glycol) (PEG), the molecular weight (MW) of the PEG dictates adsorption and desorption phenomena. Higher MW PEG chains possess increased binding affinity toward NPs, which leads to higher relative Au-NP densities on the PHEMA-g-PEG brushes and concurrent sluggish desorption of NPs by thermal stimulus. Adsorption and desorption phenomena are further modulated by NP size yielding a system where adsorption and desorption are controlled by a delicate balance between the competitive energetics of polymer brush chelation versus solvation.