We examined the effects of alkyl
carbon spacer length (CSL) and
molecular weight on fouling resistance and release properties of zwitterionic
poly(sulfobetaine methacrylate) brushes. Using surface-initiated atom
transfer radical polymerization, we synthesized two series of brushes
with CSL = 3 and 4 and molecular weight from 19 to 1500 kg ·mol–1, corresponding to dry brush thickness from around
6 to 180 nm. The brush with CSL = 3 was nearly completely wet with
water (independent of molecular weight), whereas the brush with CSL
= 4 exhibited a strong increase in water contact angle with molecular
weight. Though the two-brush series had distinct wetting properties,
both series of brushes exhibited similarly great resistance against
fouling by Staphylococcus epidermidis bacteria and Aspergillus niger fungi
spores when submerged in water, indicating that neither molecular
weight nor CSL strongly affected the antifouling behavior. We also
compared the efficacy of brushes against fouling by fungi and silicon
oil in air. Brushes grafted to filter paper were strongly fouled by
fungi and silicon oil in air. Grafting the polymers to the filter
paper, however, greatly enhanced removal of the foulant upon rinsing.
The removal of fungi and silicon oil when rinsed with a salt solution
was enhanced by 219 and 175%, respectively, as compared to a blank
filter paper control. Thus, our results indicate that these zwitterionic
brushes can promote foulant removal for dry applications in addition
to their well-known fouling resistance in submerged conditions.