**2.2. Synthesis of PMAA/Salecan/clay nanocomposites**

In order to obtain the proposed systems, two main types of hydrogels were manufactured: PMAA/clay hydrogel nanocomposites and PMAA/Salecan/clay hydrogels. The method used was adapted from the one found in the literature [3], as follows: primarily, a 0.2 g clay (ClNa, Cl30B, Cl20A and 15A) was dispersed in 14 ml of deionized water under magnetical stirring (around 800 rpm) and room temperature for 15 min. Thus, the clay dispersion was obtained and ultrasonicated for 5 min. When the hydrogels with Salecan were prepared, 0.16 g of Salecan powder was added, and the system was kept under mechanical stirring for another 15 min followed by 1 min ultrasonication.

For the PMAA/clay nanocomposites, this step was omitted. As the mass became homogenous and cooled, 2 ml MAA and 2 ml BIS (1%, w/v) were added under continuous stirring for 10 min followed by 10 min ultrasonication in an ice bath. Two milliliter APS (1.2%, w/v) was added, keeping the mass under magnetical stirring for another 5 min. The system was injected for polymerization into our own-designed glass mold. The mold was introduced into a thermostated water bath at 70°C (the desired temperature for the polymerization to occur) for 6 h.

The obtained hydrogels were cut into pieces and immersed into deionized water for 7 days. The water was changed two times a day in order to assure that the residual monomers were removed. As for analyses, the fabricated hydrogel nanocomposites were cut with an eyelet punch. One part of the cuts was deposed on polyethylene foils for water evaporation at ambient temperature for several days and the other part was freeze dried.
