Hydrophilicity-hydrophobicity adjustable polymer-modified surfaces from one-step dip-coating method

The wettability feature is a fundamental and crucial property of solid surfaces which can be easily obtained and adjusted by polymer surface treatment thanks to the wide range of properties of polymers and feasible processing methods. In this study, a simple method was developed to modify the surface of materials using amphiphilic copolymers with zwitterionic groups. Random copolymers poly(dopamine methacrylamide-co-2-(dimethylamino)ethyl methacrylate-co-sulfobetaine methacrylate) (P(DMA-co-DMAEMA-co-SBMA), PDDS) were synthesized by a "one-pot polymerization" method and successfully grafted onto the surface of the substrate by "dip-coating". As the composition of the copolymer can be easily changed, four copolymers with fixed adhesive DMA content and various SBMA contents were obtained where the hydrophilic-hydrophobic balance can be adjusted. The more hydrophobic the copolymer is, the denser and smoother the copolymer coating on silica surface will be obtained. Thus, the wettability of the copolymer modified surface can be controlled by the synergistic effect of adjusting the composition and surface morphology of the copolymer coatings. At the microscopic level, increasing the proportion of SBMA monomer could significantly enhance the hydrophilicity of the coatings, thereby decreasing the adhesive force between modified surface and colloidal probe and improving the antifouling performance of the modified surfaces. At the macroscopic level, owing to their hydrophilicity and underwater superoleophobicity, both PD5D20S75-mesh and PD5S95-mesh exhibited excellent oil/water separation performances with separation efficiency of 97.2% and 98.8%, and water flux of 40692 and 1528 L m-2 h-1, respectively. These results provide a reference for the development of hydrophilic surface materials in different applications.