Molecular Simulations of the Hydration Behavior of a Zwitterion Brush Array and Its Antifouling Property in an Aqueous Environment

Abstract

We carried out umbrella sampling and molecular dynamics (MD) simulations to investigate molecular interactions between sulfobetaine zwitterions or between sulfobetaine brushes in different media. Simulation results show that it is more energetically favorable for the two sulfobetaine zwitterions or brushes to be fully hydrated in aqueous solutions than in vacuum where strong ion pairs are formed. Structural properties of the hydrated sulfobetaine brush array and its antifouling behavior against a foulant gel are subsequently studied through steered MD simulations. We find that sulfobetaine brush arrays with different grafting densities have different structures and antifouling mechanisms. At a comparably higher grafting density, the sulfobetaine brush array exhibits a more organized structure which can hold a tightly bound hydration water layer at the interface. Compression of this hydration layer results in a strong repulsive force. However, at a comparably lower grafting density, the brush array exhibits a randomly oriented structure in which the antifouling of the brush array is through the deformation of the sulfobetaine branches.

Molecular simulations on the hydration and underwater oleophobicity of zwitterionic self‐assembled monolayers

“…Similarly, except for the peak of 0.38–0.5 nm of SB 2C ‐SAM ~ SB 6C ‐SAM, the other peaks represent that the distance between N and O within the single SB molecule (see the inset pictures of Figure 12b–f). Similar experimental results can be found in the work of Xiang et al 62 They found the similar result that the distance between the quaternary ammonium C atoms and the sulfonate O atoms within a single sulfobetaine zwitterion branch (CSL = 2) is in the range of 0.5–0.6 nm, while the distance between the two in an ion pair is about 0.3–0.35 nm. Compared with the NO RDFs in pure water, these peaks of cationic and anionic groups in salt solution (red line) get lower with the increase of CSL, especially when CSL = 3–6.…”

Recent Progress of Biomimetic Antifouling Surfaces in Marine

“…Xiang et al carried out umbrella sampling and molecular dynamics (MD) simulations, and showed that the higher grafting density sulfobetaine brush array exhibits a more organized structure which can hold a tightly bound hydration water layer at the interface. [ 61 ] Compression of this hydration layer results in a strong repulsive force. However, at a lower grafting density, the brush array exhibited a randomly oriented structure in which the repelling of the brush array was through the deformation of the sulfobetaine branches.…”

Multiscale simulations of polyzwitterions in aqueous bulk solutions and brush array configurations

“…[7][8][9] Among non-biocidal layers-which are considered to be less toxic 7 -one can find materials that are antifouling because of surface structuration (such as super-slippery sharklet technology), 10 or superhydrophobicity, 11,12 or high surface hydrophilicity. 13 Among hydrophilic, non-biocidal coatings, zwitterionic polymers [14][15][16][17][18][19][20][21][22] are considered as one of the two major classes of antifouling materials that are accessible and relatively easy to implement, the other being hydrophilic polymers based on poly(ethylene glycol) (PEG). 23,24 Brushes of zwitterionic polymers terminally grafted to a surface have been found to be effective antifouling agents, exhibiting higher chemical stability than PEG-based layers.…”

“…During the last decade there have been several atomistic 16,[19][20][21][22] and a few mesoscopic 25 simulations of the antifouling action of zwitterionic membranes. In a series of papers, Shao et al examine the influence of charged groups 16 and ions 20 on polyzwitterions, as well as the effect of the latter on proteins.…”

“…In a series of papers, Shao et al examine the influence of charged groups 16 and ions 20 on polyzwitterions, as well as the effect of the latter on proteins. 22 In a recent paper by Xiang et al, 19 brushes of terminally grafted sulfobetaine polymers were considered at different surface densities. The structure of the brushes, including ion pairs between sulfobetaine zwitterions, was explored.…”