The interplay of polymer chain interactions can create rigid (coherent) and soft (amorphous) regions that determine a polymer's solid, liquid, or melt state. The degree of crystallinity and amorphous content within PEI-C16 was estimated using the method applied by Dome et al. The amorphous and crystalline components were calculated as a ratio between the area corresponding to coherent length and the total area of the PXRD pattern (Figure ). Our analysis shows that PEI-C16, as a switchable polymer, formed nanostructures when subjected to variable pH and temperature conditions, presumably due to the prolonged acidic treatments with an acid for example, CO2. Because our CO2-responsive polymer exhibited pH-sensitive behavior, we treated the polymer with HCl (Scheme 1B, PEI-C16-H + ). After the acid treatment, the residue was When subjected to pH variations, the PXRD analysis of the polymers revealed disruption in the coherent length of alkylated PEI. All PEI-C16 samples (Figure ): pristine (PEI-C16), activated (PEI-C16*), post-desalination (PEI-C16-Cl), and acid-treated (PEI-C16-H + ) samples exhibited an X-ray diffraction peak at 2θ ≈ 21.4°, corresponding to 4.2 Å distance commonly attributed to the crystallization of comb-like polymers with alkyl side chains. 8, According to H. Shi et al. 8 , the crystallization of alkyl side chains occurs in a hexagonal lattice with an approximate distance of ~ 4.2 Å between the alkyl chains. We calculated the variations in full width at half maximum (FWHM) values of crystallite size, which implied changes in the degree of finite coherent length based on the acidic treatment and desalination experiments (Figure ). The normalized PXRD patterns provide a clearer visualization of the broadening effect of FWHM values. To better represent this effect, the table (Figure ) lists the obtained FWHM values for the diffraction peaks at 2θ ≈ 21.4°. Utilizing the Scherrer equation (eq. 3), the coherent length of the polymers was calculated, and the increased FWHM of the diffraction peak corresponded to the decreased coherence, indicative of a lower degree of molecular order (Figure ).