Abstract
This study investigated the effect of different surface-charged lamellar materials on the swelling and diffusion properties of synthesized polyacrylamide-methylcellulose hydrogels (HG). Montmorillonite and thermally activated hydrotalcite (300 °C and 550 °C) were incorporated during the preparation of nanocomposite (NC) hydrogels. A series of NC hydrogels were prepared by varying the lamellar material content (1:1, 2:1 and 4:1). The results showed that the HG with hydrotalcite (550 °C) was strongly dependent on the ionic intensity, and that the swelling degree increased by 50%, 65% and 78% with reducing the hydrotalcite content at (1:1), (2:1) and (4:1), respectively. The water absorption capacity of HG containing montmorillonite or hydrotalcite (300 ºC) was slightly affected when the pH was decreased from 7 to 3. However, the pH variation from 7 to 10 increased the water absorption capacity of most HG, except those containing hydrotalcite (550 °C) at (2:1) and (4:1). The presence of lamellar nanoparticles in hydrogels made the polymer matrix more rigid, and less likely to absorb water. In contrast, HG with hydrotalcite (550 °C) at (2:1) and (4:1) showed anomalous behavior with an increase in their water absorption capacity. The results support that the developed NC-HG can be suitable candidate materials for controlled released applications.
Highlights
Superabsorbent materials, such as hydrogels, have attracted considerable attention due to their elevated water retention capacity as well as their vast potential for application in drug release, wastewater treatment and agriculture [1,2,3,4]
This study investigated the effect of different surface-charged lamellar materials on the swelling and diffusion properties of synthesized polyacrylamide-methylcellulose hydrogels (HG)
The results showed that the HG with hydrotalcite (550 oC) was strongly dependent on the ionic intensity, and that the swelling degree increased by 50%, 65% and 78% with reducing the hydrotalcite content at (1:1), (2:1) and (4:1), respectively
Summary
Superabsorbent materials, such as hydrogels, have attracted considerable attention due to their elevated water retention capacity as well as their vast potential for application in drug release, wastewater treatment and agriculture [1,2,3,4]. The intercalation of different hydrophilic monomers – such as in polyacrylamide/methylcellulose (PAAm-MC) or carboxymethylcellulose blends – is a promising approach to increase the swelling capacity of hydrogels, while replacing part of base polymer with renewable sources. Polyacrylamide hydrogels are not biologically degraded and when replacing part of acrylamide with methylcellulose, there is a double gain: 1) insertion of glycosidic groups, which facilitates the hydrogel decomposition by bacteria and fungi; and 2) reduction of possible residues formed after the composite degradation process, contributing to minimize the toxicity potential of PAAmMC systems for environmental applications [5,6,7,8,9]. Interpenetrating polymer network (IPNs) structures are generally used to control the hydrophilicity and release kinetics of hydrogels, since they are preferable in several biomedical and biotechnological applications due to their unique properties [10]. Junior et al (2020) prepared pH-responsive poly(methacrylic acid)/laponite RDS hydrogels, and the influence of laponite on pKa, as well as the dependence between water absorption capacity and clay mineral content were evidenced [14]
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