Swelling dynamics and chain structure of ultrathin PEG membranes in seawater

Polyethylene glycol (PEG) is widely utilized in marine antifouling materials; thus, the fundamental understanding of PEG characteristics in seawater is indispensable. Herein, a "membrane-seawater" separation chamber model is designed, and the molecular dynamics (MD) method is used to simulate the swelling process of PEG membranes in seawater; two characteristic lengths are developed from the concept of Gibbs surface to illustrate the relationship between seawater ions and PEG membranes; the amount of bound water in the hydration shell of PEG is calculated by experimental method. It is concluded that the water content of the PEG membrane in seawater is not much different from that of swelling in water; only the swelling rate changes; the seawater ions accelerate the swelling of the PEG membrane, but most gathered in the outer layer of PEG membrane; Ions change the distribution structure of the hydration layer, and the bound water of PEG decreases under the action of seawater ions. Moreover, the structure of the PEG chain in seawater has a change of "helix-ring". The study of PEG in seawater will provide an effective supplement and theoretical basis for the modification design of PEG coating.