**4.1. Fourier transform infrared spectroscopy**

The presence of montmorillonite in the polymer matrix was checked by FTIR analysis (see **Figure 1**, only PMAA-ClNa and Cl15A data are presented here). FTIR spectra of Cloisites show the presence of clay characteristic peaks, confirmed also by the literature data [12, 15]. For all four types of montmorillonites, around 3633 cm−1 we noticed the OH stretching of latex water. The peak from 1011 cm−1 with a shoulder at 921 cm−1 was attributed to Si–O stretching vibration while the Si–O bending vibration was identified in the 400–600 cm−1 area, more exactly 518 cm−1 and 454 cm−1. The difference between the ClNa and the modified clays (Cl30B, Cl15A and Cl20A) is given by the presence of additional peaks at 2926 cm−1 and 2852 cm−1, specific for quaternary ammonium salts. As for the pure PMAA, its spectra reveal the characteristic peaks around 3000 cm−1 corresponding to the O–H stretching vibration and at 1737 cm−1 associated to CO group stretching vibration. At the wavelength of 2960–2875 cm−1, the peaks for stretching vibration of methyl and methylene groups were found [16]. The absence of vinyl group stretching vibration at 1628–1692 cm−1 indicates that the polymerization occurred [15].

Referring to the spectra of Salecan, a broad peak was identified at 3329 cm−1, being characteristic for O–H stretching vibration, as well as the intermolecular hydrogen bonding of the polysaccharide [17]. Peaks from the 800–1100 cm−1 area are assigned to polysaccharide structure and include C–OH stretching in the glucopyranose rings. More specifically, the band at

The Effect of Clay Type on the Physicochemical Properties of New Hydrogel Clay Nanocomposites http://dx.doi.org/10.5772/intechopen.74478 153

**Figure 1.** FT-IR spectra of the pristine clay/PMAA/PMAA-Cloisite/Salecan/PMAA-Salecan/PMAA-Salecan-Cloisite exemplified for ClNa and Cl15A.

1039 cm−1 was related to C–OH stretching in the glucopyranose ring, a broad, weak peak at 896 cm−1 suggested that D-glucopyranose had a β-configuration whereas the almost unidentifiable peak at 818 cm−1 confirmed the presence of small amounts of α-glucopyranose form.

Analyzing the spectra of the nanocomposites that have the modified montmorillonite as a component, alterations were noticed but also the preservation of some characteristic peaks. For instance, specific clay bands were observed. The Si–O–Si stretching vibration shifted from 1011 to 1050 cm−1 and the peaks from 400 to 600 cm−1 suffered a bathochromic shift. In the hydrogels, we found the Si–O bending and stretching vibration at 463 and 622 cm−1, respectively.

For the composites prepared using modified montmorillonites, the bands at 2856 and 2925 cm−1 state that the quaternary ammonium salts are present in the network. At the same time, PMAA peaks were identified. Thus, we have C═O group stretching vibration, moved from 1737 to 1697 cm−1(much lower intensity for 20A and 30B Cloisites), and the stretching vibration for methyl and methylene groups that slightly shifted to 2996–2925 cm−1 [18].

In a comparative analysis of PMAA and PMAA-Salecan bands, we noticed a change in the 2942 cm−1 peak. In the hydrogel structure, the peak broadens and suffers a decrease in sharpness, which can be explained by the formation of the intercalated structure between the polymer and the polysaccharide.

The fact that within the final structure, we find the skeleton of the compounds, we started with, serves as proof that the synthesis of semi-IPN hydrogels went successfully. The slight changes in wavelength and intensity could be explained by the interactions between the components of the hydrogels with the obtaining of a complex compact structure.
