This observation suggests that the acid treatment induces an alignment between layers, as observed in smectic-like systems which persists even after CO2-mediated desalination (Figure ). However, no alteration of distance is observed between the C16 side chains, reinforcing the robustness of this interaction upon protonation and the presence of ions and concomitant changes in the charge distributions on the amines of PEI backbone. These results, and the proposed model, served as the foundation for the 3D construction of the PEI-C16 system in DFT calculations and further encouraged investigation of the thermal stability of the PEI-C16 at each stage of the desalination process. When alkylated PEI is protonated in aq. HCl solution (0.1 N, PEI-C16-H + ), its cationic charge density increases, which may induce morphological alterations within the alkylated PEI.