Increased Donnan Exclusion at High Salt Concentrations

The swelling of univalent and multivalent charged polymeric networks in electrolytic solutions is studied using a classical thermodynamic model. Such systems were first modeled by Donnan, who derived an expression...

Analysis of Acrylic and Methacrylic Networks through Pyrolysis-GC/MS

A direct analytical method developed to characterize UV-cured networks based on multi-step pyrolysis-gas chromatography-mass spectroscopy (GC/MS) is presented. Application of the method to characterize (meth)acrylate-based UV-cured networks is discussed. The reversion process of methacrylates is clearly observed during pyrolysis. In contrast, the decomposition of acrylates in high molecular weight degradation products is hardly detected. The potential impact of this technique to elucidate the structural and compositional nature of UV-cured polymeric networks is highlighted.

ADVANCED BIOMEDICAL HYDROGELS: MOLECULAR ARCHITECTURE AND ITS IMPACT ON MEDICAL APPLICATIONS

Hydrogels are crosslinked polymeric networks swollen in water, physiological aqueous solutions, or biological fluids. They are synthesized by a wide range of polymerization methods that allow for the introduction of linear and branched units with specific molecular characteristics. In addition, they can be tuned to exhibit desirable chemical characteristics including hydrophilicity or hydrophobicity. The synthesized hydrogels can be anionic, cationic, or amphiphilic, and can contain multifunctional crosslinks, junctions or tie points. Beyond these characteristics, hydrogels exhibit compatibility with biological systems, and can be synthesized to render systems that swell or collapse in response to external stimuli. This versatility and compatibility have led to better understanding of how the hydrogel’s molecular architecture will affect their physicochemical, mechanical, and biological properties. We present a critical summary of the main methods to synthesize hydrogels which define their architecture, and advanced structural characteristics for macromolecular/biological applications.

Nano-structured dynamic Schiff base cues as robust self-healing polymers for biomedical and tissue engineering applications: a review

Polymer materials are vulnerable to damages, failures, and degradations, making them economically unreliable. Self-healing polymers, on the other hand, are multifunctional materials with superior properties of autonomic recovery from physical damages. These materials are suitable for biomedical and tissue engineering in terms of cost and durability. Schiff base linkages-based polymer materials are one of the robust techniques owing to their simple self-healing mechanism. These are dynamic reversible covalent bonds, easy to fabricate at mild conditions, and can self-reintegrate after network disruption at physiological conditions making them distinguished. Here we review self-healing polymer materials based on Schiff base bonds. We discuss the Schiff base bond formation between polymeric networks, which explains the self-healing phenomenon. These bonds have induced 100% recovery in optimal cases.

Fabrication and Characterization of Chitosan-Polyethylene Glycol (Ch-Peg) Based Hydrogels and Evaluation of Their Potency in Rat Skin Wound Model

Thermal burns are a major cause of death and suffering around the globe. They can cause debilitating, life-altering injuries as well as lead to significant psychological and financial consequences. Several research works have been conducted in attempt to find a wound healing therapy that is successful. At present, hydrogels have been widely used in cutting-edge research for this purpose because they have suitable properties. This study aimed to see how therapy with chitosan-polyethylene glycol (Ch-Peg) based hydrogels affected the healing of burn wounds in rats. With the concern of public health, xanthan gum (X), boric acid (B), gelatin (Ge), polyethylene glycol (Peg), chitosan (Ch), glutaraldehyde (G), and HPLC-grade water were prepared using X : Ge : G, X : Ge : Peg : G, X : Ge : Ch : G, X : Ge : Peg : Ch : G, X : Ge : B : Ch : G, X : Ge : B : Peg : G, and X : Ge : B : Peg : Ch : G. The produced composite hydrogels were examined for swelling ability, biodegradability, rheological characteristics, and porosity. The 3D structure of the hydrogel was revealed by scanning electron microscopy (SEM). After that, the structural characterization technique named Fourier-transform infrared spectroscopy (FTIR) was used to describe the composites (SEM). Lastly, in a rat skin wound model, the efficacy of the produced hydrogels was studied. Swelling ability, biodegradability, rheological properties, and porosity were all demonstrated in composite hydrogels that contained over 90% water. Hydrogels with good polymeric networks and porosity were observed using SEM. The existence of bound water and free, intra- and intermolecule hydrogen-linked OH and NH in the hydrogels was confirmed using FTIR. In a secondary burned rat model, all hydrogels showed significant wound healing effectiveness when compared to controls. When compared to other composite hydrogels, wounds treated with X : Ge : Peg : Ch : G, X : Ge : B : Peg : G, and X : Ge : B : Peg : Ch:G recovered faster after 28 days. In conclusion, this research suggests that X : Ge : Peg : Ch : G, X : Ge : B : Peg : G, and X : Ge : B : Peg : Ch : G could be used to treat skin injuries in the clinic.

Echogenic Advantages of Ferrogels Filled with Magnetic Sub-Microparticles

Ultrasonic imaging of ferrogels (FGs) filled with magnetic nanoparticles does not reflect the inner structure of FGs due to the small size of particles. To determine whether larger particle size would improve the acoustic properties of FGs, biocompatible hydrogels filled with 100–400 nm iron oxide magnetic sub-microparticles with weight fraction up to 23.3% were synthesized and studied. Polymeric networks of synthesized FGs were comprised of chemically cross-linked polyacrylamide with interpenetrating physical network of natural polysaccharide—Guar or Xanthan. Cylindrical samples approximately 10 mm in height and 13 mm in diameter were immersed in a water bath and examined using medical ultrasound (8.5 MHz). The acoustic properties of FGs were characterized by the intensity of reflected echo signal. It was found that the echogenicity of sub-microparticles provides visualization not only of the outer geometry of the gel sample but of its inner structure as well. In particular, the echogenicity of FGs interior depended on the concentration of magnetic particles in the FGs network. The ultrasound monitoring of the shape, dimensions, and inner structure of FGs in the applied external magnetic field is demonstrated. It is especially valuable for the application of FGs in tissue engineering and regenerative medicine.

Degree-Based Topological Properties of Molecular Polymeric Networks Composed by Sierpinski Networks

Sierpinski graphs are a widely observed family of fractal-type graphs relevant to topology, Hanoi Tower mathematics, computer engineering, and around. Chemical implementations of graph theory establish significant properties, such as chemical activity, physicochemical properties, thermodynamic properties, and pharmacological activities of a molecular graph. Specific graph descriptors alluded to as topological indices are helpful to predict these properties. These graph descriptors have played a key role in quantitative structure-property/structure-activity relationships (QSPR/QSAR) research. The objective of this article is to compute Randic index ( R − 1 / 2 ), Zagreb index M 1 , sum-connectivity index SCI , geometric-arithmetic index GA , and atom-bond connectivity ABC index based on ev-degree and ve-degree for the Sierpinski networks S n , m .

Synthesis, crystal structure, and quantum mechanical studies regarding a new metal–organic complex based on Cd (II)

A novel metal-organic complex formulated as [Cd (phen)(dipic) (H2O)2]. 3 H2O (phen = 1, 10-phenanthroline; dipic2−= pyridine-2,6-dicarboxylate) has been hydrothermally synthesized at 150°C for 48h. The structure of Cd complex was characterized by elemental analysis, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential thermal analysis (DTA), and single-crystal X-ray diffraction (SC-XRD). The crystal system of Cd complex is monoclinic with space group C 2/c. The pentagonal bipyramid (seven coordinate) around Cd2+ center filled by two terminal water ligands, one 1,10-phenanthroline, and one pyridine-2,6-dicarboxylate anion. Extensive O–H···O hydrogen bonding interactions involving all coordinated water molecules, dipicolinate oxygens, and crystallization water molecules further stabilize the complex units by linking them to form three-dimensional polymeric networks. Indeed, quantum mechanical studies were performed to understand effective factors on stability of the Cd(II) complex.