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Abstract
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 - 1500 kg mol-1, corresponding to dry brush thickness from around 6 - 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 carbon spacer length 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.
Supplementary materials
Title
Supporting Information
Description
NMR spectra of the synthesized monomers and polymers in solution (Figure S1); GPC refractometer data for the unbound polymers in solution (Figure S1); differential scanning calorimetry and thermogravimetric analysis data for polyMABS (Figure S2); SI-ATRP reaction conditions and characteristics of polyMAPS and polyMABS brush samples (Table S1); static, advancing, and receding water contact angles as a function of brush thickness and images of water droplets during advancing and receding measurements (Figure S3); polyMABS contact angle in salt solutions (Figure S4); schematic illustration of SI-ATRP of MAPS and MABS on filter paper and characterization with FTIR and static contact angle measurements (Figure S5); images of the incubated blank and polyMAPS-, and polyMABS-grafted filter papers with A. niger spores (Figure S6); fungi (Figure S7) and silicon oil (Figure S8) removal percentage of polyMAPS and polyMABS-grafted filter paper; calculation of the gravitational force of a sedimenting fungi spore on brushes.
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