"Hydration Dynamics and Structure of Charge-Screened Polymeric Zwitterions"

S. Mengel^a, A. Destefano^a, T. Webber^a, A. Semerdjiev^a, G. Wu^b, W. Guo^b, Z. Chen^b, S. Han^c, R. Segalman^a,d,e

^aDepartment of Chemical Engineering, University of California, Santa Barbara, 93106 / ^bDepartment of Chemistry, University of Michigan, Ann Arbor, 48103 / ^cDepartment of Chemistry, Northwestern University, Evanston, 60208 / ^dDepartment of Materials, University of California, Santa Barbara, 93106 / ^eDepartment of Chemistry & Biochemistry, University of California, Santa Barbara, 93016

Polymeric zwitterions exhibit exceptional fouling resistance through formation of a strongly hydrated surface of immobilized water molecules. While extensively tested for application-specific performance, the characteristics of this hydration layer and the role of molecular design on broad fouling resistance remain unclear. In this work, Overhauser dynamic nuclear polarization (ODNP) relaxometry and sum frequency generation (SFG) vibrational spectroscopy analyze the hydration dynamics and structure of polymeric zwitterions over salt conditions of a range of common antifouling applications. These zwitterions are found to possess rapid water diffusion within their first 2-3 hydration shells, which accelerate toward bulk behavior in highly saline, charge-screened environments. Faster dynamics correlate with a measurable reduction in bound surface water through weakened electrostatic interactions. Furthermore, charge delocalization is identified as a useful parameter for tuning the hydration structure and dynamics around polymeric zwitterions. SFG spectroscopy reveals that delocalized zwitterions form more hydrated surfaces. This finding correlates with ODNP measurements, which show slower water dynamics for delocalized zwitterions, potentially as a result of increased hydrophobic interactions.

This research was primarily supported by the Office of Naval Research awards N00014-16-1-2960, N00014-20-1-2152, N00014-20-1-2234, and N00014-23-1-2127. Polymer synthesis and purification leveraged shared experimental facilities supported by the BioPACIFIC Materials Innovation Platform of the National Science Foundation under Award No. DMR-1933487. Magnetic resonance experiments leveraged shared experimental facilities supported by the NSF MRSEC program under Award No. DMR 1720256. SDM acknowledges support from the National Science Foundation Graduate Research Fellowship (DGE 2139319).