Nötr makromoleküller üzerinde spesifik iyon ve eş çözünmezlik etkileri

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", which ranks the anions and cations based on their ability to increase or decrease the solubility of macromolecules. It is known that the weakly-hydrated anions can interact with macromolecules, while the strongly hydrated ones are excluded 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. In the second part, "cononsolvency" which is an important phenomenon that occurs when two good solvents decrease the solubility of the macromolecule when they are mixed. For understanding the mechanism of this phenomenon, poly(N-isopropylacrylamide) (PNIPAM) and poly (N, N - diethylacrylamide) (PDEA) were used as model macromolecules. PNIPAM showed cononsolvency behavior via the addition of methanol, ethanol, and isopropanol, while PDEA did not exhibit the same anomaly, rather showed cosolvency. Attenuated Total Reflection – Fourier Transform Infrared (ATR-FTIR) spectroscopy combined with Multivariate Curve Resolution (MCR) analysis showed that both the changes in the bulk properties of solvent-cosolvent mixtures and the hydration shell of the macromolecules in the collapsed state cause the cononsolvency behavior for PNIPAM. Our results show that the interface and preferential alcohol adsorption dictate the cononsolvency phenomenon.