Electrically conducting silver/guar gum/poly(acrylic acid) nanocomposite

Metal-Filled Polyvinylpyrrolidone Copolymers: Promising Platforms for Creating Sensors

This paper presents research results on the properties of composite materials based on cross-linked grafted copolymers of 2-hydroxyethylmethacrylate (HEMA) with polyvinylpyrrolidone (PVP) and their hydrogels filled with finely dispersed metal powders (Zn, Co, Cu). Metal-filled pHEMA-gr-PVP copolymers in the dry state were studied for surface hardness and swelling ability, which was characterized by swelling kinetics curves and water content. Copolymers swollen in water to an equilibrium state were studied for hardness, elasticity, and plasticity. The heat resistance of dry composites was evaluated by the Vicat softening temperature. As a result, materials with a wide range of predetermined properties were obtained, including physico-mechanical properties (surface hardness 240 ÷ 330 MPa, hardness number 0.06 ÷ 2.8 MPa, elasticity number 75 ÷ 90%), electrical properties (specific volume resistance 10² ÷ 10⁸ Ω⋅m), thermophysical properties (Vicat heat resistance 87 ÷ 122 °C), and sorption (swelling degree 0.7 ÷ 1.6 g (H₂O)/g (polymer)) at room temperature. Resistance to the destruction of the polymer matrix was confirmed by the results concerning its behavior in aggressive media such as solutions of alkalis and acids (HCl, H₂SO₄, NaOH), as well as some solvents (ethanol, acetone, benzene, toluene). The obtained composites are characterized by electrical conductivity, which can be adjusted within wide limits depending on the nature and content of the metal filler. The specific electrical resistance of metal-filled pHEMA-gr-PVP copolymers is sensitive to changes in moisture (with a moisture increase from 0 to 50%, ρ_V decreases from 10⁸ to 10² Ω⋅m), temperature (with a temperature change from 20 °C to 175 °C, ρ_V of dry samples decreases by 4.5 times), pH medium (within pH from 2 to 9, the range of ρ_V change is from 2 to 170 kΩ⋅m), load (with a change in compressive stress from 0 kPa to 140 kPa, ρ_V of swollen composites decreases by 2-4 times), and the presence of low molecular weight substances, which is proven by the example involving ethanol and ammonium hydroxide. The established dependencies of the electrical conductivity of metal-filled pHEMA-gr-PVP copolymers and their hydrogels on various factors, in combination with high strength, elastic properties, sorption capacity, and resistance to aggressive media, suggest the potential for further research as a platform for the manufacture of sensors for various purposes.

Functional Enhancement of Guar Gum−Based Hydrogel by Polydopamine and Nanocellulose

The development of green, biomedical hydrogels using natural polymers is of great significance. From this viewpoint, guar gum (GG) has been widely used for hydrogel preparation; however, its mechanical strength and adhesion often cannot satisfy the biomedical application. Therefore, in the present study, gelatin and a cellulose nanocrystal (CNC) were first applied to overcome the defects of guar gum hydrogel. Dopamine was self−polymerized into polydopamine (PDA) on the gelatin chain at alkaline condition, and gelatin−polydopamine (Gel−PDA) further cross−linked with guar gum and CNC via the borate−didiol bond, intramolecular Schiff base reaction, and Michael addition. CNC not only interacted with guar gum using borate chemistry but also acted as a mechanical reinforcer. The obtained Gel−PDA+GG+CNC hydrogel had an excellent self−healing capacity, injectability, and adhesion due to the catechol groups of PDA. Moreover, dopamine introduction caused a significant increase in the anti−oxidant activity. This hydrogel was cyto− and hemo−compatible, which implies a potential usage in the medical field.

New Materials Based on Polyvinylpyrrolidone-Containing Copolymers with Ferromagnetic Fillers

The article investigates the peculiarities of the effect of ferromagnetic fillers (FMFs) of various natures (Ni, Co, Fe, FeCo, SmCo₅) on the formation of the structure and properties of 2-hydroxyethylmethacrylate (HEMA) with polyvinylpyrrolidone (PVP) copolymers. The composites were characterized using FTIR-spectroscopy, SEM, DMTA, magnetometry of vibrating samples, specific electrical resistivity studies, and mechanical and thermophysical studies. The formation of a grafted spatially crosslinked copolymer (pHEMA-gr-PVP) was confirmed and it was established that the FMF introduction of only 10 wt.% into the copolymer formulation increased the degree of crosslinking of the polymer network by three times. The surface hardness of composites increased by 20–25%. However, the water content decreased by 16–18% and lay within 42–43 wt.%, which is a relatively high number. The heat resistance of dry composites was characterized by Vicat softening temperature, which was 39–42 °C higher compared to the unfilled material. It was established that the obtained composites were characterized by a coercive force of 200 kA × m⁻¹ and induction of a magnetic field at the poles of 4–5 mT and 10–15 mT, respectively. The introduction of FMF particles into pHEMA-gr-PVP copolymers, which, in the dry state, are dielectrics, provides them with electrical conductivity, which was evaluated by the specific volume resistance. Depending on the FMF nature and content, as well as their orientation in the magnetic field, the resistance of filled materials could be regulated within 10²–10⁶ Ohm·m. Therefore, the modification of HEMA with PVP copolymers by ferromagnetic fillers of various natures provides the possibility of obtaining materials with unique predicted properties and expands the fields of their use, for instance as magnetic sorbents for various applications, as well as the possibilities associated with their being electrically conductive materials that can respond by changing of electrical conductivity, depending on various factors.

Photopolymerizable Biomaterials and Light-Based 3D Printing Strategies for Biomedical Applications

Since the advent of additive manufacturing, known commonly as 3D printing, this technology has revolutionized the biofabrication landscape and driven numerous pivotal advancements in tissue engineering and regenerative medicine. Many 3D printing methods were developed in short course after Charles Hull first introduced the power of stereolithography to the world. However, materials development was not met with the same enthusiasm and remained the bottleneck in the field for some time. Only in the past decade has there been deliberate development to expand the materials toolbox for 3D printing applications to meet the true potential of 3D printing technologies. Herein, we review the development of biomaterials suited for light-based 3D printing modalities with an emphasis on bioprinting applications. We discuss the chemical mechanisms that govern photopolymerization and highlight the application of natural, synthetic, and composite biomaterials as 3D printed hydrogels. Because the quality of a 3D printed construct is highly dependent on both the material properties and processing technique, we included a final section on the theoretical and practical aspects behind light-based 3D printing as well as ways to employ that knowledge to troubleshoot and standardize the optimization of printing parameters.

Recent advances in soft functional materials: preparation, functions and applications

Synthetic materials and biomaterials with elastic moduli lower than 10 MPa are generally considered as soft materials. Research studies on soft materials have been boosted due to their intriguing features such as light-weight, low modulus, stretchability, and a diverse range of functions including sensing, actuating, insulating and transporting. They are ideal materials for applications in smart textiles, flexible devices and wearable electronics. On the other hand, benefiting from the advances in materials science and chemistry, novel soft materials with tailored properties and functions could be prepared to fulfil the specific requirements. In this review, the current progress of soft materials, ranging from materials design, preparation and application are critically summarized based on three categories, namely gels, foams and elastomers. The chemical, physical and electrical properties and the applications are elaborated. This review aims to provide a comprehensive overview of soft materials to researchers in different disciplines.

Guar gum and its composites as potential materials for diverse applications: A review

Naturally occurring polymers are currently of prime importance among which polysaccharides occupies superior position due to their easy availability, eco- friendly and non-toxic nature. Guar gum, one of the naturally occurring polymer, is a galactomannan acquired by ground endosperm of Cyamopsis tetragonolobus or Cyamopsis psoraloides. It belongs to the family leguminosae. Presence of large number of hydroxyl groups increases its H- bonding ability when dissolved in water that enhance the viscosity and gelling properties of the guar gum solution. Based upon these properties, guar gum is used in several industries such as textile, food, petrochemical, mining and paper for varied applications. It is used as suspending, emulsifying, gelling and stabilising agent in the conventional dosage forms. Last few decades have marked the increase in development of various composites of guar gum that have intrinsic utilization in various fields. Immobilization of guar gum with the others not only enhances its properties but also enriches its utilization in numerous fields for diverse applications such as water purification, drug delivery, pharmaceutical, cosmetic and food industries, etc. Guar gum derivatives are found to have therapeutic importance in certain physiological disorders also. In this review article, we have summarized various possible composites of guar gum and their most probable applications in different fields.

Guar gum-crosslinked-Soya lecithin nanohydrogel sheets as effective adsorbent for the removal of thiophanate methyl fungicide

Rapid increase in use of fungicides for the agricultural and industrial purposes has marked the deterioration of water resources which ultimately affects the human life. Accordingly, various attempts have been made in the removal of these noxious compounds. In the same context, we are presenting biopolymers based nanohydrogel sheets; guar gum-crosslinked-Soya lecithin nanohydrogel sheets (GG-crosslinked-SY NHS) used for the effective removal of a fungicide; thiophanate methyl from aqueous solution. Guar gum and soya lecithin were employed as the biopolymers in the fabrication of nanohydrogel sheets due to their non- toxic nature, easy availability, cheapness and significant properties. Due to the presence of highly reactive functional groups onto the surface of GG-crosslinked-SY NHS, good adsorption results have been obtained. Maximum adsorption capacity of 59.205mg/g was observed with 20mg GG-crosslinked-SY NHS and 25ppm thiophanate methyl solution concentration as calculated from the Langmuir isotherm. Results showed that neutral pH favoured the adsorption process. Kinetics results were indicative of the physical interactions between the thiophanate methyl and GG-crosslinked-SY NHS surface. Thermodynamic results have shown the spontaneous and endothermic adsorption process.

Silver nanoparticles-containing dual-function hydrogels based on a guar gum-sodium borohydride system

Dual-function hydrogels, possessing both stimuli-responsive and self-healing properties, have recently attracted attention of both chemists and materials scientists. Here we report a new paradigm using natural polymer (guar gum, GG) and sodium borohydride (NaBH₄), for the preparation of silver nanoparticles (AgNPs)-containing smart hydrogels in a simple, fast and economical way. NaBH₄ performs as a reducing agent for AgNPs synthesis using silver nitrate (AgNO₃) as the precursor. Meanwhile, sodium metaborate (NaBO₂) (from NaBH₄) behaves as a cross-linking agent between GG molecular chains. The AgNPs/GG hydrogels with excellent viscoelastic properties can be obtained within 3 min at room temperature without the addition of other cross-linkers. The resultant AgNPs/GG hydrogels are flowable and injectable, and they possess excellent pH/thermal responsive properties. Additionally, they exhibit rapid self-healing capacity. This work introduces a facile and scale-up way to prepare a class of hydrogels that can have great potential to biomedical and other industrial applications.

Hydrogels 2.0: improved properties with nanomaterial composites for biomedical applications

The incorporation of nanomaterials in hydrogels (hydrated networks of crosslinked polymers) has emerged as a useful method for generating biomaterials with tailored functionality. With the available engineering approaches it is becoming much easier to fabricate nanocomposite hydrogels that display improved performance across an array of electrical, mechanical, and biological properties. In this review, we discuss the fundamental aspects of these materials as well as recent developments that have enabled their application. Specifically, we highlight synthesis and fabrication, and the choice of nanomaterials for multifunctionality as ways to overcome current material property limitations. In addition, we review the use of nanocomposite hydrogels within the framework of biomedical and pharmaceutical disciplines.

Composites of Polymer Hydrogels and Nanoparticulate Systems for Biomedical and Pharmaceutical Applications

Due to their unique structures and properties, three-dimensional hydrogels and nanostructured particles have been widely studied and shown a very high potential for medical, therapeutic and diagnostic applications. However, hydrogels and nanoparticulate systems have respective disadvantages that limit their widespread applications. Recently, the incorporation of nanostructured fillers into hydrogels has been developed as an innovative means for the creation of novel materials with diverse functionality in order to meet new challenges. In this review, the fundamentals of hydrogels and nanoparticles (NPs) were briefly discussed, and then we comprehensively summarized recent advances in the design, synthesis, functionalization and application of nanocomposite hydrogels with enhanced mechanical, biological and physicochemical properties. Moreover, the current challenges and future opportunities for the use of these promising materials in the biomedical sector, especially the nanocomposite hydrogels produced from hydrogels and polymeric NPs, are discussed.

Utilization of hydroxypropyl carboxymethyl cellulose in synthesis of silver nanoparticles

Hydroxypropyl carboxymethyl cellulose samples having varying degrees of substitution and varying degrees of polymerization were used to reduce silver nitrate to silver nanoparticles. UV spectral analysis of silver nanoparticles colloidal solution reveal that increasing the pH of the reduction solution leads to improvement in the intensity of the absorption band for silver nanoparticles, to be maximum at pH 11. The absorption peak intensity also enhanced upon prolonging the reaction duration up to 60 min. The conversion of silver ions to metallic silver nanoparticles was found to be temperature-dependent and maximum transformation occurs at 60 °C. The reduction efficiency of hydroxypropyl carboxymethyl cellulose was found to be affected by its degree of polymerization. Colloidal solutions of silver nanoparticles having concentration up to 1000 ppm can be prepared upon fixing the ratio between silver nitrate and hydroxypropyl carboxymethyl cellulose at 0.017-0.3g per each 100ml of the reduction solution.

Nanoparticle-Hydrogel Composites: Concept, Design, and Applications of These Promising, Multi-Functional Materials

New technologies rely on the development of new materials, and these may simply be the innovative combination of known components. The structural combination of a polymer hydrogel network with a nanoparticle (metals, non-metals, metal oxides, and polymeric moieties) holds the promise of providing superior functionality to the composite material with applications in diverse fields, including catalysis, electronics, bio-sensing, drug delivery, nano-medicine, and environmental remediation. This mixing may result in a synergistic property enhancement of each component: for example, the mechanical strength of the hydrogel and concomitantly decrease aggregation of the nanoparticles. These mutual benefits and the associated potential applications have seen a surge of interest in the past decade from multi-disciplinary research groups. Recent advances in nanoparticle-hydrogel composites are herein reviewed with a focus on their synthesis, design, potential applications, and the inherent challenges accompanying these exciting materials.