Zwitterionic surface modification of polyethylene via atmospheric plasma-induced polymerization of (vinylbenzyl-)sulfobetaine and evaluation of antifouling properties

Zwitterionic polymer brushes were grafted from bulk polyethylene (PE) by air plasma activation of the PE surface followed by radical polymerization of the zwitterionic styrene derivative (vinylbenzyl)sulfobetaine (VBSB). Successful formation of dense poly-(VBSB)-brush layers was confirmed by goniometry, IR spectroscopy, XPS and ToF-SIMS analysis. The resulting zwitterionic layers are about 50-100 nm thick and cause extremely low contact angles of 10 degrees (water) on the material. Correspondingly we determined a high density of > 1.0 x 1016 solvent accessible zwitterions/cm2 (corresponding to 2,0 *10-8 mol/cm2) by a UV-based ion-exchange assay with crystal violet. The elemental composition as determined by XPS and characteristic absorption bands in the IR spectra confirmed the presence of zwitterionic sulfobetaine polymer brushes. The antifouling properties of the resulting materials were evaluated in a bacterial adhesion test against gram-positive bacteria (S. aureus). We observed significantly reduced cellular adhesion of the zwitterionic material compared to pristine PE. These microbio-logical tests were complemented by tests in natural seawater. During a test period of 21 days, confocal micro-scopy revealed excellent antifouling properties and confirmed the operating antifouling mechanism. The procedure reported herein allows the efficient surface modification of bulk PE with zwitterionic sulfobetaine polymer brushes via a scalable approach. The resulting modified PE retains important properties of the bulk material and has excellent and durable antifouling properties.

Automated summary

Zwitterionic polymer brushes were successfully grafted from bulk polyethylene via air plasma activation and radical polymerization. The resulting layers showed a low contact angle and a high density of solvent accessible zwitterions. Antifouling properties were confirmed through bacterial adhesion tests and seawater tests.