MSc in Chemistry Thesis Defense
by Yaren Şevval Özdoğan
Title: Ion Specificity and Cononsolvency Effects on Neutral Macromolecules
Advisor: Asst. Prof. Halil Ibrahim Okur
Date: September 9, 2025
Time: 11.00
Place: Chemistry Department Meeting Room (SB Building, 1. Floor)
Abstract:
Ions, osmolytes, and other small molecules can interact with macromolecules and affect their properties, such as solubility and hydration. The ion specificity has been an important research topic since Franz Hofmeister published the “Hofmeister Series” that ranks the anions and cations based on their ability to increase or decrease the solubility of the macromolecules. It is known that the weakly-hydrated anions can interact with macromolecules, while the strongly hydrated ones exclude from the macromolecular surface due to having strongly interacting hydration shells. In this thesis, the ion specific effects are extended to sugar-based macromolecules from commonly studied amide-based ones. Methylcellulose (MC), hydroxypropyl cellulose (HPC), and dextran were utilized as model polymers for investigating whether the Hofmeister anions can interact or not. Lower Critical Solution Temperature (LCST) measurements showed that MC and HPC are affected by the Hofmeister anions with the same way as the amide-based macromolecules. Namely, SCN- act as a surface-active ion, and salts-in whereas SO42- ion salts-out macromolecules via ion exclusion mechanism.
The proton nuclear magnetic resonance (1H-NMR) spectroscopy measurements showed that the methyl groups of MC are responsible for the interaction between the Hofmeister anions and the polymer.