**3.2. X-ray diffraction**

These hydrophilic-hydrophobic complex systems are foreseen to find application in controlled drug release where *co*-delivery of polar-unpolar substances at the target site is mandatory.

Commercial clays ClNa, Cl30B, Cl20A and Cl15A were kindly offered by Southern Clay Products Inc. PMAA (polymethacrylic acid, Janssen Chimica), Salecan (Souzhou Chemicals), N, N′-methylenebisacrylamide (Sigma Aldrich) and ammonium persulfate (Sigma Aldrich)

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

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)

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 ambi-

The FTIR spectra were obtained by a Fourier transform infrared spectrophotometer BRUKER Tensor on ATR mode in the range of the scanning wave numbers 4000–400 cm−1 with a 40 scans per sample cycle and a resolution of 4 cm−1. Milled samples were used for FTIR analyses.

ent temperature for several days and the other part was freeze dried.

**2. Experimental**

were used as received.

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

150 Current Topics in the Utilization of Clay in Industrial and Medical Applications

15 min followed by 1 min ultrasonication.

**2.1. Materials**

for 6 h.

**3. Characterization**

**3.1. Fourier transform infrared spectroscopy**

Powder X-ray diffraction was used for phase identification of the crystalline material and to determine the lattice parameters of the crystal structure. A multifunctional system powder X-ray diffractometer, Rigaku Ultima IV (Tokyo, Japan), was used to perform the measurements. The equipment conditions were as follows: X-ray generator was operated at 40 kV voltage and 30 mA current, using Cu target (CuKα radiation, λ = 1.5406 Å); the goniometer was set in parallel beam geometry system, with cross beam optics (CBO), θ-θ scanning mode and with a step width of 0.02°; a scintillation counter was used. For low angle measurements, the optics used were DS and SS (divergence and scattering slits) = 1°, RS (receiving slit) = 0.2° and receiving side Soller slit 0.5°, collecting data between 0.6 < 2θ < 6° measuring range, with a scanning speed of 1°/min. For wide angle measurements, the optics used were DS (divergence slit) = 1°, SS and RS (scattering and receiving slits) = open and receiving side Soller slit 0.5°, collecting data between 3 < 2θ < 50° measuring range, with a scanning speed of 2°/min. The measurements were performed in the continuous mode, at room temperature and atmospheric pressure.
