Synthesis of super absorbent polymer using citric acid as a bio-based monomer

Natural and Synthetic Polymers for Biomedical and Environmental Applications

Natural and synthetic polymers are a versatile platform for developing biomaterials in the biomedical and environmental fields. Natural polymers are organic compounds that are found in nature. The most common natural polymers include polysaccharides, such as alginate, hyaluronic acid, and starch, proteins, e.g., collagen, silk, and fibrin, and bacterial polyesters. Natural polymers have already been applied in numerous sectors, such as carriers for drug delivery, tissue engineering, stem cell morphogenesis, wound healing, regenerative medicine, food packaging, etc. Various synthetic polymers, including poly(lactic acid), poly(acrylic acid), poly(vinyl alcohol), polyethylene glycol, etc., are biocompatible and biodegradable; therefore, they are studied and applied in controlled drug release systems, nano-carriers, tissue engineering, dispersion of bacterial biofilms, gene delivery systems, bio-ink in 3D-printing, textiles in medicine, agriculture, heavy metals removal, and food packaging. In the following review, recent advancements in polymer chemistry, which enable the imparting of specific biomedical functions of polymers, will be discussed in detail, including antiviral, anticancer, and antimicrobial activities. This work contains the authors' experimental contributions to biomedical and environmental polymer applications. This review is a vast overview of natural and synthetic polymers used in biomedical and environmental fields, polymer synthesis, and isolation methods, critically assessessing their advantages, limitations, and prospects.

Superabsorbent hydrogels based on natural polysaccharides: Classification, synthesis, physicochemical properties, and agronomic efficacy under abiotic stress conditions: A review

Superabsorbent polymers (SAPs) are a class of polymers that have attracted tremendous interest due to their multifunctional properties and wide range of applications. The importance of this class of polymers is highlighted by the large number of publications, including articles and patents, dealing with the use of SAPs for various applications. Within this framework, this review provides an overview of SAPs and highlights various key aspects, such as their history, classification, and preparation methods, including those related to chemically or physically cross-linked networks, as well as key factors affecting their performance in terms of water absorption and storage. This review also examines the potential use of polysaccharides-based SAPs in agriculture as soil conditioners or slow-release fertilizers. The basic aspects of SAPs, and methods of chemical modification of polysaccharides are presented and guidelines for the preparation of hydrogels are given. The water retention and swelling mechanisms are discussed in light of some mathematical empirical models. The nutrient slow-release kinetics of nutrient-rich SAPs are also examined on the basic of commonly used mathematical models. Some examples illustrating the advantages of using SAPs in agriculture as soil conditioners and agrochemical carriers to improve crop growth and productivity are presented and discussed. This review also attempts to provide an overview of the role of SAPs in mitigating the adverse effects of various abiotic stresses, such as heavy metals, salinity, and drought, and outlines future trends and prospects.

An eco-friendly composite hydrogel based on covalently crosslinked cellulose/poly (glycerol citrate) for thallium (Ι) removal from aqueous solutions

Cellulose/poly (glycerol citrate) reinforced with thiol-rich polyhedral oligomeric silsesquioxane and apple peel (POSS-SH@CAG-CEL/AP) was synthesized using gelation method in the presence of glutaraldehyde as a crosslinker agent and used as an efficient composite hydrogel for elimination of Tl(Ι) from aqueous solutions. This composite hydrogel and synthesized thiol-rich polyhedral oligomeric silsesquioxane were characterized by elemental analysis, FT-IR, NMR, TGA, and FE-SEM techniques. The effects of synthetic and environmental parameters on the adsorption capacity of the composite hydrogel were investigated and it was found that thiol-rich polyhedral oligomeric silsesquioxane has improved the hydrogel properties including the Tl(Ι) uptake and the thermal stability. The maximum adsorption capacity of 352.3 mg g-1 was obtained within 30 min under optimum reaction conditions. A typical Langmuir adsorption isotherm with was observed for adsorption of Tl(I) onto POSS-SH@CAG-CEL/AP and pseudo-second-order kinetic model provided the best correlation between experimental data. Thermodynamic studies showed that the Tl(I) adsorption was spontaneous process and exothermic. Also, the reusability tests confirmed that the POSS-SH@CAG-CEL/AP can be reused for four times without any remarkable change in its adsorption capacity. Thus, this reusable biobased composite hydrogel can be an ideal candidate for elimination of Tl(I) from aqueous solutions.

Synthesis and property of superabsorbent polymer based on cellulose grafted 2-acrylamido-2-methyl-1-propanesulfonic acid

An eco-friendly superabsorbent polymer (SAP) was prepared by grafting 2-acrylamido-2-methyl-1-propanesulfonic acid onto microcrystalline cellulose in lithium chloride/N, N-dimethylacetamide system. The synthesized SAP (cellulose-g-PAMPS) was characterized by FTIR, TGA, SEM, ¹H NMR, ¹³C NMR and XRD. The water absorption equilibrium of cellulose-g-PAMPS could be achieved within 10 min in distilled water. Moreover, the maximum water absorption capacities of cellulose-g-PAMPS in distilled water, 0.9 wt% NaCl solution and 3.2 wt% Na₂CO₃ solution were 648.9, 298.4 and 207.3 g·g^-1, respectively. The water absorption behavior of cellulose-g-PAMPS was interpreted by the pseudo-second-order model. Furthermore, cellulose-g-PAMPS could be used in some extreme conditions due to its high acid and alkali resistance. The water retention rate of cellulose-g-PAMPS could be maintained above 90 % at 25 °C for 6 h. As a consequence, the synthesized SAP can be applied to increase the plant growth and survival time under drought conditions, even under saline alkali conditions.

Computational Approach to the Surface-Crosslinking Process of Superabsorbent Polymer via Central Composite Design

The improvement of gel strength and absorption properties through the surface-crosslinking of superabsorbent polymers (SAPs) is essential for sanitary industry applications. We prepared core-SAP via aqueous solution copolymerization, and then surface-crosslinked the core-SAP under various conditions. The structure of the SAP was characterized using Fourier transform infrared (FT-IR) spectroscopy. Central composite design (CCD) of response surface methodology (RSM) has been applied to determine the optimum surface-crosslinking conditions such as surface-crosslinker content, reaction temperature, and reaction time. The optimal surface-crosslinking conditions were identified at a surface-crosslinker content of 2.22 mol%, reaction temperature of 160 °C, and reaction time of 8.7 min. The surface-crosslinked SAP showed excellent absorbency under load of 50 g/g with a permeability of 50 s. Other absorption properties were also evaluated by measuring the free absorbency and centrifuge retention capacity in saline solution.

A Novel Superabsorbent Polymer from Crosslinked Carboxymethyl Tragacanth Gum with Glutaraldehyde: Synthesis, Characterization, and Swelling Properties

Nowadays, current global environmental problems include measures to eliminate or reduce the negative impact of chemicals from petroleum sources and, therefore, the use of materials from natural resources is increasingly recommended. In this context, natural-based superabsorbent polymers derived from polypeptides and polysaccharides have undergone chemical and biochemical modifications to improve their ability to absorb and retain large amounts of liquids. In the present paper, a new process has been used to overcome the side effects of radical polymerization in the manufacture of conventional polyacrylate superabsorbents (SAPs). Tragacanth gum (TG) was selected to prepare a new superabsorbent material (CMTG-GA) based on carboxymethyl tragacanth (CMTG) crosslinked with glutaraldehyde (GA). The characterization of the polymer was carried out by FTIR, TGA, XRD, and SEM. The effect of the amount of crosslinking agent and the pH on the water absorption capacity was also examined. Subsequently, swelling studies were performed using free swelling capacity (FSC) and centrifuge retention capacity (CRC) techniques in distilled water, tap water, and saline solution. The results showed that the CRC of the new material is not less than 42.1 g/g, which was observed for a ratio of 20% by weight of GA to CMTG. Likewise, the maximum absorption results were 43.9 and 32.14 g/g, respectively, for FSC and CRC at pH 8.0. In addition, a comparison of the swelling capacities of the synthesized product with a commercial SAP extracted from a baby diaper, well known in the Moroccan market, showed that the performances were very similar.

Synthesis, characterization, and the antioxidant activity of N,N,N-trimethyl chitosan salts

Chitosan, possessing excellent properties, has been drawing broad attention. For the further utilization of chitosan, chemical modification is performed in improving its water solubility and the bioactivities. In the current study, four N,N,N-trimethyl chitosan salts, including N,N,N-trimethyl chitosan citrate (TMCSCi), N,N,N-trimethyl chitosan acetylsalicylate (TMCSAc), N,N,N-trimethyl chitosan ascorbate (TMCSAs), and N,N,N-trimethyl chitosan gallate (TMCSGa), were prepared via N,N,N-trimethyl chitosan iodide (TMCSI). The as-prepared products were characterized by FT-IR and ¹H NMR. Meanwhile, the degrees of substitution were calculated by elemental analysis results. Furthermore, scavenging activities (against DPPH radicals and superoxide radicals) test and reducing power test were selected to evaluate the antioxidant property of N,N,N-trimethyl chitosan salts in vitro. The results indicated that TMCSAs and TMCSGa displayed excellent activity, probably due to the enhancement of ascorbate and gallate in antioxidant activity. However, because of the weak antioxidant property of citrate and acetylsalicylate, the activity was lower for TMCSCi and TMCSAc. For example, in the DPPH radicals scavenging assay, the scavenging rates of chitosan, TMCSI, TMCSCi, TMCSAc, TMCSAs, and TMCSGa were 25.22, 84.11, 6.90, 2.70, 94.92, and 96.75% at 0.4 mg/mL, respectively. Generally, TMCSAs and TMCSGa could be regarded as a potential source of antioxidants.