Stimuli-responsive polymers, which alter their properties in response to environmental changes, offer a novel and potentially energy-saving approach for water purification and regeneration. Various smart polymer systems can remove pollutants effectively from water absorption, thus allowing us to access materials with higher performance in desalination and water purification, requiring highly energy-efficient processes compared to the modern reverse osmosis membrane processes. Herein, we employed various techniques, viz. nuclear magnetic resonance (NMR) spectroscopy, powder X-ray diffraction (PXRD), small-angle X-ray scattering (SAXS), and inelastic neutron scattering (INS), to investigate the chemical and physical nature of CO2responsive hydrophobically modified PEIs. To compare their structural behavior under CO2 conditions with carbonic acid, we subjected alkylated PEIs to aq. HCl solution, mimicking its influence in CO2 capture and anion exchange sequences. Our analyses showed the impact of CO2 inducing spontaneous protonation and subtle disruptions in the hydrophobic domains of alkylated PEI, thus forming new nanostructures.