Molecular simulations on the hydration and underwater oleophobicity of zwitterionic self‐assembled monolayers
Zheng Chen, Mingrui Liao, Li‐Zhi Zhang, Zhou Jian
Abstract
Abstract Zwitterionic materials have attracted increasing attentions in the underwater super‐oleophobic applications for its strong hydration via electrostatic interactions. Herein, molecular dynamics simulations were used to investigate the hydration and underwater oleophobicity of sulfobetaine‐terminated self‐assembled monolayers (SB‐SAMs) with different carbon spacer lengths (CSL) between oppositely charged groups of SB molecules. Simulation results show that the hydration of SB‐SAMs is positively dependent on CSL; the underwater oleophobicity is strengthened and then weakened with the increase of CSL, reaching optimal performance when CSL = 3; adhesion force of oil droplet on SB‐SAMs is inversely correlated with their contact angles, reaching the minimum value when CSL = 3. Moreover, the addition of NaCl can weaken the self‐association of SB molecules resulted from interactions between cationic and anionic groups, which promotes hydration and enhances underwater oleophobicity of SB‐SAMs. These results will benefit for the design of novel zwitterion‐based materials for anti‐fouling and oil–water separation applications.