In Situ Probing of the Surface Hydration of Zwitterionic Polymer Brushes: Structural and Environmental Effects

Abstract

Surface hydration has been proposed as the key nonfouling mechanism of zwitterionic materials. Because these materials have various chemical structures and will be used in complex environments, in situ probing of their surfaces in different aqueous environments is crucial to understanding their surface hydration properties. In this work, the surfaces of three zwitterionic polymer brushes in aqueous solutions with salts or varied pH were probed using sum frequency generation (SFG) vibrational spectroscopy. The SFG spectra indicate the ordering of the polymer brushes in water and the strong hydrogen bonding of the interfacial water molecules. The ordering of water at the surfaces of carboxybetaine polymers changed with pH, but at the sulfobetaine polymer surface, this ordering was not affected by pH. The interfacial ordering of water also decreased when salt ions were associated with the polymers. Ions from different salts had different interfacial binding affinities depending on the ion type and the polymer structure, as deduced from the interfacial water signals. These SFG results reveal important surface hydration properties of zwitterionic polymers that will guide their applications in complex environments.

Salt-Responsive Zwitterionic Polymer Brushes with Tunable Friction and Antifouling Properties

“…These results are consistent with the sum frequency generation (SFG) vibrational spectroscopy results as reported by Leng et al, 24 i.e. sulfonbetain polymer binds divalent cations more strongly than monovalent cations.…”

“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 This indicates that polyVBIPS binds K + more strongly than Na + , in agreement with previous simulation and experiment results. 24,34 . As compared to monovalent cations, MgCl 2 and CaCl 2 further decreased contact angles to ~35 ° and ~32 °, respectively.…”

Probing the Surface Hydration of Nonfouling Zwitterionic and PEG Materials in Contact with Proteins

“…The SFG spectroscopy was implemented according to the protocol reported previously. 33 Briefly, the visible and infrared (IR) input beams penetrated a right angle prism and overlapped spatially and temporally at the sample surface or interface. The incident angles of the visible and IR beams were 60° and 54° with respect to the surface normal, and the pulse energies of the visible and IR beams were 30 and 100 µJ, respectively.…”

Revisiting the Challenges in Fabricating Uniform Coatings with Polyfunctional Molecules on High Surface Energy Materials

“…As water comes in contact with surfaces of hydrophilic or polar materials, the structure of water at the interface differs from the bulk, and interferes with mechanical and chemical behaviors of surfaces and materials (Figure 6a). Therefore, the interfaces in exposure to water or humidity gain significant importance not only to control mechanical and chemical behavior of surface and material, but also to explore new applications [6,54,[80][81][82][83][84][85][86]. Even though understanding of this bound water layer remains incomplete, it has been shown that the changes in structure of water are dominated by hydrogen bond networks and its dynamic evolution [82,[87][88][89].…”

“…In some hydrogels, however, bound water layer let to higher Young's moduli (stronger mechanical properties) as compared to the ones filled only with bulk water [6]. In another example, the presence of bound water on surfaces was reported to prevent fouling of materials, thus used to promote antifouling properties of surfaces [80,84]. The bound water content may be reduced in vacuum or high temperature environment and increased by exposing to water vapor, aqueous environment or humidity.…”