2. Experimental study

#### 2.1. Materials

1. Introduction

142 Hydrogels

in conjunction with other polymers [7, 8].

an easy way to create gel [9].

antibacterial activity [10].

absorption properties [15, 16].

Hydrophilic membranes based on hydrogels can be defined as a polymeric material, which is insoluble in water, can absorb it and retain a significant fraction in its structure [1]. The material that forms the membranes with these characteristics is composed of two water-insoluble crosslinked hydrophilic polymer systems, due to the existence of a three-dimensional network

Hydrogels can be expanded by water and ion absorption, above the equilibrium state and retain their original shape and mechanical properties. In addition, they present permeability to biologically active substances with low molecular weight, being used in dressings directly on contact with the skin and can be used as dressing or bandage in burn wounds, vascular prostheses, artificial cartilage membranes for hemodialysis, among other applications [5, 6].

Hydrogels obtained by ionizing radiation, having as precursors poly(n-vinyl-2-pyrrolidone) (PVP), agar and plasticizing agents such as polyethylene glycol that have been used in pharmaceuticals and have advantages over the previously obtained methods, they eliminate the sterilization phase, as this is still being obtained in the process of ionizing radiation [1].

Due to its properties, PVAl is one of the synthetic polymers that are used as a biomaterial, being of great importance in the industry, mainly in cosmetics, where it is used as an additive, providing texture to the products. Its main function is that of a plasticizer. Its use in the synthesis of hydrophilic membranes presents some restrictions when used alone, because the obtained membrane presents low elasticity and rigidity. To improve these properties, it is used

Chitosan is a natural polymer that can be obtained through the process of deacetylation of chitin, a polysaccharide of great abundance in nature, and present a similar chain to cellulose. Among its main characteristics, of great importance and industrial interest, it is atoxic and has

Chitosan nanocomposites have been used in the cotton coating for application in dressings and bandage with the purpose of increasing the absorption of the exudate as well as improving the

Chitosan and PVAl are biocompatible polymers being in the composition of several hydrogels used today [11, 12]. Hydrophilic membranes based on PVAl and chitosan have been synthesized because the presence of chitosan improves the mechanical, hydrophilic and antibacterial properties of membranes obtained from PVAl [13, 14]. These membranes modified by the presence of nanoclays for use in dressings have been obtained with good mechanical and

Hydrophilic membranes obtained from polyvinyl alcohol, poly(N-vinylpyrrolidone) and anti-

The pseudoboehmite obtained by the sol-gel process is a ceramic nanoparticle with high surface area, bioinert, which can be used in drug delivery systems [18]. Pseudoboehmite has the same structure as the boehmite (ɣ-ALOOH). It has an orthorhombic structure and presents two layers of octahedral oxygen partially filled with aluminum cations [19]. Through the sol:

biotic containing chitosan have been synthesized by Yu et al. [17].

connecting their chains, and is perceived that water was retained in its structure [2–4].

The following reagents were used: aluminum nitrate Al(NO3)3, supplied by Dinâmica LTDA; ammonium hydroxide (NH4OH), supplied by Audaz Reagente Tecnológico; polyvinyl alcohol, supplied by Bandeirante Química; poly(N-vinyl-2-pyrrolidone) (PVP), supplied by GAF Co.; chitosan, supplied by Polymar; poly(ethylene glycol), supplied by Oxiteno Brasil and agar supplied by Oxide.

#### 2.2. Methods

The synthesis of nanoparticles of pseudoboehmite (PSB): The nanoparticles of the pseudoboehmite were obtained through the sol-gel process, according to Munhoz Jr. et al. [22], aluminum nitrate solution in H2O, solution of ammonium nitrate in H2O and solution of polyvinyl alcohol in H2O, which is used to increase the viscosity of the aluminum nitrate solution. The solution of aluminum nitrate and polyvinyl alcohol was mixed with the ammonium hydroxide solution. The obtained product was washed with distilled water and dried through air.

Obtaining chitosan solution: The chitosan was dissolved in acetic acid solution, 2 wt% in H2O, which was stirred for 48 h. After dissolution of chitosan, it was neutralized with 1 wt% sodium hydroxide solution in H2O until pH 7.

Preparation of PVP/PVAl/PSB/chitosan membranes reinforced with PSB: Membranes with 3 wt% PSB were obtained. Table 1 shows the composition of the membranes obtained.

The hydrogels were produced from a solution of PVP, PVAl, chitosan, agar and PEG in H2O, which was heated and subsequently PSB was added to the solution. The solution was poured into polyethylene molds and after cooling, a physical gel was obtained.


thermodynamic-mechanical properties were determined in a Perkin Elmer equipment in the range from 80 to 0C. The rate used in analysis was 1C/min with 40 mL/min

Obtaining Hydrogels based on PVP/PVAL/Chitosan Containing Pseudoboehmite Nanoparticles for Application…

http://dx.doi.org/10.5772/intechopen.72007

145

Visual characterization: Figure 1 shows the obtained membranes with 25 kGy dose.

The membranes with the compositions 1, 2, 3 and 4 (Figure 1) are transparent, while others are translucent and slightly yellowish. Therefore, the presence of chitosan makes the hydrogels

In the membranes with the compositions 1, 2, 3 and 4 were firm and without bubbles, the membranes of compositions 5, 6, 7 and 8 showed a greater adhesion or tack due to the

Tensile strength: Table 2 and Figures 2 and 3 present the results to the tensile strength tests to

The results show that comparing the obtained hydrogels, the Comp. 4 (based on PVP/PVAl/ 3wt% agar) and Comp. 3 (based on PVP/PVAl/chitosan/3wt% agar) (Figure 2) showed higher

The hydrogels Comp. 1 (PVP/1wt% agar), Comp. 2 (PVP/3wt% agar), Comp. 7 (PVP/PVAl/ chitosan/PBS/1wt% agar) and Comp. 8 (PVP/PVAl/chitosan/PSB)/3wt% agar) exhibit lower

Figure 1. Comp. 1 (PVP/1wt% agar); Comp. 2 (PVP/3 wt% agar); Comp. 3 (PVP/PVAl/1 wt% agar); Comp. 4 (PVP/PVAl/ 3wt% agar), Comp. 5 (PVP/PVAl/chitosan/1 wt% agar), Comp. 6 (PVP/PVAl/chitosan/3wt% agar); Comp. 7 (PVP/PVAl/

chitosan/PSB)/1wt% agar) and Comp. 8 (PVP/PVAl/chitosan/PSB/3 wt% agar).

The Comp. 2 hydrogels (PVP/3 wt% agar) (Figure 3) show the smallest elongation.

nitrogen flow.

less transparent.

3. Results and discussion

presence of chitosan (Figure 1).

tensile strength and higher elongation.

7 days after irradiation.

tensile strength (Figure 2).

Table 1. Membranes composition.

The physical gel was irradiated in Dynamitron electron beam, with energy of 1.5 MeV, with a dose of 25 kGy and a dose rate of 11.3 kGy/s, which promoted the formation of the cross-links and also the sterilization of the material.

#### 2.2.1. Characterization of hydrogels

Hydrogels were characterized by visual test, mechanical test, gel fraction, thermal properties and swelling.


$$\text{Sol}-\text{gel fraction } (\text{wt}\%) = (\text{Wfg}/\text{Wi}) \times 100\tag{1}$$

where Wfg = final weight (after drying); and Wi = initial weight of the sample.

• Swelling: The samples were maintained in water for 240 h. The water absorption was checked every hour step in the first 24 h. After that, each measurement was performed using 24-h steps until reaching constant weight. The hydration grade was determined by the difference of the weight before and after swelling according to Eq. (2).

$$\text{Swelling} \left( \text{wt\%} \right) = \left[ \left( \text{Wfs} - \text{Wi} \right) / \text{Wi} \right] \times 100 \tag{2}$$

where Wfs = final weight (after swelling); and Wi = initial weight of the sample.

• Thermal properties (DTA, TG and DTMA): Thermal analyses were performed by the Netzsch Thermische Analyze STA 409 equipment. The rate used in DTA and TG analysis was 10�C/min from ambient temperature until 600�C with 40 mL/min nitrogen flow. The thermodynamic-mechanical properties were determined in a Perkin Elmer equipment in the range from 80 to 0C. The rate used in analysis was 1C/min with 40 mL/min nitrogen flow.
