Grafting density and antifouling properties of poly[N-(2-hydroxypropyl) methacrylamide] brushes prepared by “grafting to” and “grafting from”†
Antifouling polymer brushes are widely utilized in biomedical applications to prevent non-specific interactions with biological fluids. They consist of surface-tethered polymer chains and are commonly formed when the chains are “grafted to” (GT) a surface by chemisorption or “grafted from” (GF) a surface in a surface-initiated polymerization. Although the antifouling polymer brushes have been studied for years, an accurate comparison between the GT and GF methods in terms of the ability of the prepared brushes to resist fouling has not been established yet. In this study, we investigate physical and antifouling properties of poly[N-(2-hydroxypropyl) methacrylamide] (poly(HPMA)) brushes synthesized by GT and GF methods using reversible addition–fragmentation chain-transfer (RAFT) polymerization. Using size exclusion chromatography and single-molecule force spectroscopy, we are able to ensure that grafted polymer chains in the layers prepared by both methods have comparable composition and molar mass. Thus, we attribute the differences in fouling resistance and physical properties of the polymer layers to the physical conformation of the chains achieved by the selected grafting method. While both types of poly(HPMA) brushes are shown to substantially reduce fouling from blood plasma, the GF polymer brushes suppress fouling by an order of magnitude better than the GT polymer brushes. The observed difference in the antifouling performance is related to the much higher grafting density that can be achieved in the GF method. This study highlights the importance of the selection of the grafting method for achieving a high antifouling performance.