İyon Hareketliliği-Kütle Spektrometrisi Tekniği Kullanılarak Uyaranlara Duyarlı Polielektrolitlerin Konformasyonel Özelliklerinin Analiz Edilmesi

Abstract

Ion mobility-mass spectrometry (IM-MS) is an analytical technique, and the interest in this technique has been growing in parallel with advancements in technology, particularly due to its ability to offer high sensitivity, high resolution, and the capability to analyze low amounts of samples. Today, the IM-MS technique has become an exceptionally valuable analytical method in the field of polymer characterization. The ability to monitor and differentiate conformational features of polymer chains within complex polymer samples in the gas phase places this technique at a significant advantage compared to other separation methods, such as chromatography, which relies on a stationary phase. The conformational dynamics of polyelectrolytes can vary depending on various parameters, such as the pH of the solution, ambient temperature, type/composition of the solvent, and the nature of the additives present. In this thesis, the effects of these types of parameters on different polyelectrolyte structures were analyzed using the trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) technique. Characterization of four different polyelectrolytes was provided. These polyelectrolytes are Poly-L-Lysine (PLL), Polystyrene Sulfonic Acid (PSS), Polyglutamic Acid (PGA), and Polyacrylic Acid (PAA). While all the polyelectrolytes used, except for PLL, have polyanion characteristics, PLL is a polycation. Initially, the analyses of these polyelectrolytes at different capillary voltages ranging from 1500V to 4500V were conducted and their conformational responses were analyzed. It was observed that the four polyelectrolytes did not respond to the differences in capillary voltage under the prepared and applied conditions. In another set of analyses, different solvent types were used to observe variations. Solvents such as water, 10 mM ammonium acetate, acetonitrile, and methanol were used to observe differences in the conformations of the four polyelectrolytes. However, it was noted that solvent changes did not have an effect similar to capillary voltage. The responses of sodium and potassium-adducted polyelectrolyte ions to growth were measured. It was determined that the gas-phase structures of sodiated and potassiated polyelectrolyte ions became increasingly tighter in the order of PLL > PSS > PGA > PAA. Finally, changes in conformations with respect to temperature variations were observed. Analyses were conducted by increasing the temperature from 60°C to 300°C in 60°C increments. It was observed that as the temperature increased, ion mobility increased, resulting in reduced contact with the carrier gas and, thus, a decrease in the collision cross-section (CCS). Additionally, due to the strong acidic and basic nature of PLL and PSS, they were observed to be less affected by temperature changes compared to PAA and PGA. The data obtained and the evaluations conducted in this thesis have the potential to provide a unique perspective on the analysis of conformational properties of stimuli-responsive polymers, such as polyelectrolytes.