Zwitterionic polymer brush-functionalized dual-crosslinked hydrogel via subsurface-initiated atom transfer radical polymerization for anti-fouling applications

In this work, a double-network (DN) hydrogel embedded with initiator (HHy–Br) was prepared and then reinforced with Fe³⁺, after which the antifouling polymer (poly-sulfobetaine vinyl imidazole, PSBVI) was successfully grafted onto the HHy-Br substrate via subsurface-initiated atom transfer radical polymerization (sSI-ATRP) to obtain PSBVI-functionalized HHy-Br (HHy-PSBVI). It has been demonstrated that Fe³⁺ can increase the crosslinking density of HHy–Br; as a result, the tensile strength of the as-prepared hydrogel was increased from 0.07 to 1.75 MPa, as well as its anti-swelling properties were improved (from 648 % to 219 %). In addition, the presence of Fe³⁺ can efficiently promote the sSI-ATRP process. Compared with HHy–Br, the PSBVI-functionalized HHy-Br manifested a significant decrease in friction coefficient, as the grafted high-thickness PSBVI brush (about 200 μm) has excellent hydrophilicity and can form a strong hydration layer for lubrication. Furthermore, the as-prepared HHy-PSBVI also exhibits outstanding antibacterial properties against E. coli (nearly 100 % were removed) and S. aureus (99 % were removed), as well as a satisfactory antifouling effect against microalgae (93 % Dunaliella and 92 % Chlorella were removed), which is attributed to the synergistic effect between the strong hydration of the zwitterionic polymer and the good bactericidal effect of the cationic imidazole group.