Abstract
In the present work, the interaction mechanism of specific polyelectrolyte multilayers (PEMs), fabricated by layer-by-layer deposition of polydiallyldimethylammonium chloride (PDDA) and poly(sodium 4-styrenesulfonate) (PSS), is studied using atomic force microscopy. The underwater oil-repellency of PSS-capped PEMs was further explored by measuring the interaction forces between tetradecane droplets and PEMs-coated silica substrates under various salinities. The force curves were analyzed following the Stokes–Reynolds–Young–Laplace theoretical model. Desirable consistency was achieved between the experimental and theoretical calculations at low NaCl concentrations (0.1 mM and 1 mM); however, underestimation of the attractive force was found as the NaCl concentration increases to moderate (10 mM) and high (100 mM) levels. Discrepancy analyses and incorporated features toward a reduced surface charge density were considered based on the previous findings of the orientation of anionic benzenesulfonate moieties (Liu et al. in Angew Chem Int Ed 54(16):4851–4856, 2015. https://doi.org/10.1002/anie.201411992). Short-range steric hindrance interactions were further introduced to simulate “brush” effect stemming from nanoscale surface roughness. It is demonstrated in our work that the PSS-capped PEMs remains a stable underwater lipophobicity against high salinity, which renders it potential application in surface wetting modification and anti-fouling.
Highlights
IntroductionKey Laboratory of Environmental Protection Technology on Water Transport, Tianjin Research Institute for Water Transport Engineering, Tianjin 300456, China oil/water separation, in relation to industrial engineering applications such as in agricultural pesticide, electric power transmission, detergents, petroleum production, material modification, and biomedicine (Zheng et al 2010; Guo et al 2012; Song et al 2019; Rostami et al 2019; Ehsan et al 2019; Luo et al 2016; Sudha et al 2019; Ahmadi et al 2020)
poly(sodium 4-styrenesulfonate) (PSS)-capped (PDDA/ PSS)4.0 polyelectrolyte multilayers (PEMs) was found to exhibit stable oil-repellency, the reduced surface charge density stems from benzenesulfonate reorientation, which occurred upon tight contact with oil droplet (Jin et al 2019). (Fig. S1 in Supporting Information)
The same trend was deduced between a (PDDA/PSS)4.0-coated tip and a (PDDA/PSS)4.0 substrate
Summary
Key Laboratory of Environmental Protection Technology on Water Transport, Tianjin Research Institute for Water Transport Engineering, Tianjin 300456, China oil/water separation, in relation to industrial engineering applications such as in agricultural pesticide, electric power transmission, detergents, petroleum production, material modification, and biomedicine (Zheng et al 2010; Guo et al 2012; Song et al 2019; Rostami et al 2019; Ehsan et al 2019; Luo et al 2016; Sudha et al 2019; Ahmadi et al 2020). The deposition of polyelectrolytes, as one of the prevalent methods for surface modification, has demonstrated superior advantages in the hydrophilization of charged surfaces due to the macromolecules’ particular molecular configuration and strong electrostatically induced hydration (Chang et al 2016). PSS-capped (PDDA/ PSS)4.0 PEMs was found to exhibit stable oil-repellency, the reduced surface charge density stems from benzenesulfonate reorientation, which occurred upon tight contact with oil droplet (Jin et al 2019). (Fig. S1 in Supporting Information)
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