Chemistry & Biochemistry Colloquium | Exploring the Binding of Ions to Polymers in Aqueous Salt Solutions, April 18

The Chemistry & Biochemistry Colloquium Series features Dr. Paul Cremer discussing "Exploring the Binding of Ions to Polymers in Aqueous Salt Solutions" on April 18  at 4:10 p.m. in Walter 245.

Cremer is the J. Lloyd Huck Professor of Chemistry and of Biochemistry and Molecular Biology in the Eberly College of Science at Penn State University.

Abstract : Hofmeister series chemistry has been a focus of both fundamental and industrial interest since it was first discovered over 130 years ago. It can be shown that a wide variety of physical phenomena follow a recurring rank ordering for both cations and anions when water, organic molecules and salts are mixed. Examples include the hydrophobic collapse and aggregation of macromolecules, the turnover rate of enzymes, the pickling of cucumbers, and even the transfer of charge between ice particles in a lightning storm. Using a combination of spectroscopic techniques, thermodynamic measurements as well as simulations, it is now possible to elucidate key molecular level details of Hofmeister series behavior. In this presentation, the solubility of thermoresponsive polymers in the presence of salts will be discussed. The results show that weakly hydrated anions bind along polymer chains in locations where the hydrogen bonding is most greatly disrupted. Curiously, this makes shorter oligomers less soluble compared to longer polymers possessing the same chemical constituents in NaSCN, NaI, or NaClO ₄ solutions. Moreover, weakly hydrated anions interact more strongly than cations with uncharged polymer chains. In fact, metal cations rarely come to the polymer/water interface without being accompanied by counter anions.

Weakly hydrated anions bind to polymers but not monomers in aqueous solutions
Bradley A. Rogers, Halil I. Okur, Chuanyu Yan, Tinglu Yang, Jan Heyda, Paul S. Cremer
Nat. Chem. 14 (2022), 40-45 The Molecular Mechanism for the Interactions of Hofmeister Cations with Macromolecules in Aqueous Solution
Ellen E. Bruce, Halil I. Okur, Sina Stegmaier, Chad I. Drexler, Bradley A. Rogers, Nico F. A. van der Vegt,  Sylvie Roke, Paul S. Cremer
J. Am. Chem. Soc., 142 (2020) 19094-19100