Hydration and Mobility of Poly(ethylene oxide) Brushes

Abstract

Poly­(ethylene oxide) (PEO) hydration is an important factor determining brush properties and application efficacy. Using atomistic molecular dynamics simulations, we investigate hydration, static, and dynamic properties of PEO brushes on gold surface as functions of grafting density, σ. We found that at lower grafting densities PEO is well-hydrated except for the surface vicinity where we observe PEO adsorption substituting for the water layering. In pure THF or mixed THF/water solvent, there is no PEO adsorption on gold surface with water preferentially residing inside the PEO layer and THF forming a thin layer near the gold surface. In aqueous solutions, an increase in the grafting density results in PEO stretching away from the surface, the loss of hydration, and a steplike density profile with the brush height satisfying the expected σ1/3 scaling. We show that PEO hydration in the brush is the same as in aqueous solutions of the corresponding water content. While the residence time of hydrogen-bonded water increases, the hydration shell and PEO tail mobility are found to decrease substantially with an increase in grafting density, indicating that these properties associated with protein inhibition capability may be compromised in a dense brush.

Molecular Dynamics Simulations of Strain-Induced Phase Transition of Poly(ethylene oxide) in Water

“…8 The intriguing properties of PEO in water were already considered in previous simulation studies using different force fields and degree of coarse-graining. [9][10][11][12][13] Recently, Dahal and Dormidontova 14,15 have studied the hydration, static and dynamic properties of PEO chains both in aqueous solutions and grafted to the surface using atomistic molecular dynamics simulations.…”

Polymer brushes in solid-state nanopores form an impenetrable entropic barrier for proteins

“…Still, the theory of brushes as kinetic barriers is hard to verify experimentally. This is mainly because regardless of whether protein adsorption is detected or not for a given system, the role of potential polymer-surface interactions outcompeting the protein adsorption 7 (equilibrium prevention) cannot be distinguished from the kinetic barrier effect. For instance, although surface plasmon resonance (SPR) can confirm qualitatively that brushes have protein excluding properties, [8][9][10] it does not provide the concentration profile perpendicular to the surface.…”

Investigation of design parameters in generating antifouling and lubricating surfaces using hydrophilic polymer brushes

“…Although QCM‐D cannot differentiate between the trapped and solvated H 2 O molecules, the hydration behavior at these low densities are not further commented in our current study. Dahal et al . employed atomistic molecular dynamic simulations and observed a similar decrease in the number of hydrogen bonds per monomer and an increase in the residence time for hydrogen‐bound H 2 O in the hydration shell with an increase in the density of the poly(ethylene oxide) chains on the surface.…”

“…Recent studies, however, have also shown that the local solvation structures influence the structural transitions in chains leading to chain stiffening and enhanced film rigidity . The interdependence of chain flexibility and the amount of hydrated H 2 O on brush properties, especially for PEG and PMOXA brushes have not been studied in detail previously.…”