## 2 Results and Discussion  
### Characteristics of Synthesized REEIIPs and Hybrid Materials  
Synthesized polymers and nanotubes were analyzed with several techniques. Among others, the FTIR was carried out, and the corresponding spectra are presented in Figure 1. Many characteristic absorption peaks confirming the chemical structure of the synthesized polymers could be observed. For example, in the modified chitosan, the interaction between the chitosan matrix and the aldehyde through the formation of new imine linkages was confirmed by the band at 1621 cm\({}^{-1}\). A shift in the position of characteristic bands when compared to the pure chitosan that could confirm the formation of chitosan Schiff base could also be observed, i.e., the characteristic bands at 3361 and 3291 cm\({}^{-1}\) corresponding to N-H and O-H stretching were shifted in the Schiff base-like product to 3462 and 3331 cm\({}^{-1}\). The absorption bands at 2921 and 2877 cm\({}^{-1}\), attributed to the C-H symmetric and asymmetric stretching, were shifted to 2945 and 2890 cm\({}^{-1}\). These bands are generally characteristic for polysaccharides. The residual \(N\)-acetyl groups were confirmed by the band at 1621 cm\({}^{-1}\) (C=O stretching at amide I) and a band shift from 1329 to 1283 cm\({}^{-1}\) (C-N stretching of amide II). The band shift from 1589 to 1621 cm\({}^{-1}\) corresponds to the N-H bending in the product. The shift in the absorption band from 1153 to 1136 cm\({}^{-1}\) can be attributed to the stretching of the C-O-C bridge, while the bands at 1283 and 1186 cm\({}^{-1}\) could correspond to C-N stretching after the formation of the Schiff base. The absorption at 1431 cm\({}^{-1}\) is associated most probably with the hydroxy groups of chitosan. The band at 1621 cm\({}^{-1}\) could be assigned to C=C bonds associated with the skeletal vibrations. In our case, the absorption bands between 1500 and 1750 cm\({}^{-1}\) correspond to the C=N bonding, so the band at 1621 cm\({}^{-1}\) could be associated with this bonding. Figure 1: _Cont._  
Figure 1: FTIR spectra of the following: (**a**) modified chitosan, (**b**) NdIIPs, (**c**) PrIIPs, (**d**) GdIIPs, (**e**) MWCNT--PrIIPs, and (**f**) MWCNT—GdIIPs. It could be seen that the FTIR spectra of the REEIIPs are similar because these materials were synthesized with the same precursors and by the same methodology. However, some differences could be observed, especially connected with various ternary complexes. FTIR spectra confirmed the successful incorporation of functional groups characteristic of modified chitosan and REEIIPs (Nd, Pr, Gd). For all of the REEIIP samples, it was found that the REE ions were bound by nitrogen atoms, due to the change in the C=N band around 1690 cm\({}^{-1}\) for DCQ [42], to 1633 cm\({}^{-1}\) for NdIIPs, to 1643 cm\({}^{-1}\) for PrIIPs, and to 1595 cm\({}^{-1}\) for GdIIPs. Also, the peak around 1700 cm\({}^{-1}\) could confirm the presence of a hydrogen bond bridge and the ternary complex. However, there are some changes in the position of characteristic bands that could be related to the creation of a cross-linked structure and preorganization of the ligands by the template. The absence of bands in the region of 1683 cm\({}^{-1}\) indicated the absence of a vinyl group, confirming the successful polymerization. It was also possible to detect in each polymer the presence of polystyrene absorption bands associated with the stretching of the C=O group at 1633 cm\({}^{-1}\) for NdIIPs, at 1643 cm\({}^{-1}\) for PrIIPs, and at 1595 cm\({}^{-1}\) for GdIIPs, and the C-O group at 1114 cm\({}^{-1}\) for NdIIPs, at 1464 cm\({}^{-1}\) for PrIIPs, and at 1100 cm\({}^{-1}\) for GdIIPs. The transformation into the REEIIPs was confirmed by the presence of C-N aromatic amine stretching bands at 1214, 1305, and 1276 cm\({}^{-1}\) for Nd, Pr, and GdIIPs, respectively. Figure 1e,f show exemplary FTIR spectra for MWCNTs modified with PrIIPs and GdIIPs, respectively.