Thermoresponsive, Pyrrolidone-Based Antifouling Polymer Brushes

Commonly, modification of surfaces with thermoresponsive polymers is performed using poly(N-isopropylacrylamide) (poly(NIPAM)). However, integration of poly(NIPAM) with a second polymer to obtain more complex copolymer structures has proven challenging due to inherently poorly controllable polymerization characteristics of acrylamides. In this study, (N-(2-methacryloyloxyethyl)pyrrolidone (NMEP) is synthesized and polymerized under controlled conditions from silicon oxide substrates via surface-initiated atom transfer radical polymerization (SI-ATRP) to produce thermoresponsive poly(NMEP) brushes. The livingness of the brushes is demonstrated by reinitiation of poly(NMEP) brushes using oligo(ethylene glycol) methyl ether methacrylate to obtain diblock copolymer brushes. Following extensive characterization, the reversible thermoresponsive behavior of these poly(NMEP) brushes is demonstrated using phase-controlled AFM topography measurements in an aqueous liquid environment. These measurements indicate that at 27 °C the poly(NMEP) brushes are solvated and extend away from the surface, whereas at 60 °C the polymers are insoluble and reside in a collapsed conformation. Finally, to investigate the potential applicability of poly(NMEP) brushes in biomedical devices, the antifouling properties of the coating are tested in aqueous media containing BSA, fibrinogen, or 10% diluted human serum using quartz crystal microbalance with dissipation monitoring (QCM-D). These measurements reveal very good antifouling properties, even when exposed to 10% diluted human serum.