Compressive Strength Of Hydrogel Research Articles

Developing biomass-modified hydrogel with high mechanical strength by a rosin-based crosslinking agent

Hydrogels are used in diverse applications owing to their superior water absorption and flexibility. At present, preparing hydrogels with high mechanical strength is becoming a hot topic. Hence, acrylpimaric acid-based acrylamide (APAAM) crosslinker were prepared from acrylpimaric acid, a derivative of natural rosin. The APAAM crosslinker synthesized a series of N, N-dimethylacrylamide/acrylamide (DMAA/AM) biomass-modified hydrogels with different crosslinking agent additions. The chemical structure, surface morphology, mechanical properties, rheological properties, and swelling properties of DMAA/AM hydrogels were investigated. The results showed that the tensile strength and compressive strength of hydrogels with APAAM (2.16 MPa, 874%) as a crosslinker are 15 times higher than the hydrogel with N, N′-methylene diacrylamide (BIS) (0.142 MPa, 254%) as crosslinker. This improvement benefit from the introduction of a rosin rigid ring. The swelling and thermal stability properties of hydrogels with APAAM as the crosslinker are also better than those of hydrogels prepared with BIS as the crosslinker. Besides, the mechanical strength and swelling properties of the hydrogels can be adjusted by the addition of an APAAM crosslinking agent. It was believed that this work provided a significant method for developing favorable mechanical properties for biomass-modified hydrogels.

Study of double network hydrogels based on sodium methacrylate alginate and carboxymethyl chitosan

Based on sodium methacrylate alginate (MASA) and carboxymethyl chitosan (CMCS), double network (DN) hydrogels were formed by covalent crosslinking and physical crosslinking in succession. Covalent crosslinking was achieved by using poly(ethylene glycol) diacrylate (PEGDA) as the crosslinker and initiated by ammonium persulfates, while physical crosslinking was realized by the electrostatic interactions between the carboxyl group of MASA and the amino group of CMCS induced by acetic acid atmosphere. With the addition of PEGDA (1.25 wt% of mixture solution), the compressive strength of hydrogel was increased from 9.0 kPa to 73.3 kPa. Compared with the physically cross-linked hydrogels, the light transmittance of the DN hydrogels at 600 nm was significantly increased from 23.7% to 93.8%. The drug release studied by taking berberine hydrochloride hydrate (Ber) as the model drug showed that drug release behaviors of the DN hydrogels were pH sensitive and notably correlated with the content of PEGDA. In addition, DN hydrogels existed excellent water absorption rate (38.3-fold). Therefore, the enhanced mechanical properties, high transparency, excellent water absorption rate, and pH sensitivity of the DN hydrogel suggested the promising applications of the hydrogels as visual transdermal drug delivery systems.

Coordination with zirconium: A facile approach to improve the mechanical properties and thermostability of gelatin hydrogel.

The poor mechanical property and thermostability restricted applications of gelatin hydrogel. Herein, a facile and inexpensive approach of immerging cooling induced gelatin hydrogels into Zr(SO4)2 dilute solution was applied to overcome these shortages. After this treatment, the micropores in hydrogel decreased to tens of microns while the water content slightly decreased. XPS results revealed that the coordination bonds formed between amino or carboxyl groups of gelatins and Zr4+. After immerging in 0.06M Zr4+ solution, mechanical tests showed that the elastic modulus, compressive modulus and compressive strength of hydrogel were about 400, 1192 and 476kPa, respectively, which were approximate 100, 11 and 5 times larger than those of pure gelatin. The DSC data indicated that the thermoreversible temperature of triple helix structure in gelatin was improved from about 30°C to 55°C. More importantly, the rheological temperature sweep test revealed that hydrogels with 0.06M Zr4+ treatment can maintain the hydrogel state without melting even at 80°C. CCK-8 tests and Calcein-AM/PI double-stain experiments demonstrated Zr4+ coordination was non-cytotoxic. These promising data indicated this nontoxic method was efficient and had potential to fabricate gelatin related materials for further application.

Preparation and Swelling Behaviors of High-Strength Hemicellulose-g-Polydopamine Composite Hydrogels.

Hemicellulose-based composite hydrogels were successfully prepared by adding polydopamine (PDA) microspheres as reinforcing agents. The effects of PDA microsphere size, dosage, and nitrogen content in hydrogel on the mechanical and rheological properties was studied. The compressive strength of hydrogel was increased from 0.11 to 0.30 MPa. The storage modulus G’ was increased from 7.9 to 22.0 KPa. The gaps in the hemicellulose network are filled with PDA microspheres. There is also chemical cross-linking between them. These gaps increased the density of the hydrogel network structure. It also has good water retention and pH sensitivity. The maximum cumulative release rate of methylene blue was 62.82%. The results showed that the release behavior of hydrogel was pH-responsive, which was beneficial to realizing targeted and controlling drug release.

Role of Ionic Moieties in Hydrogel Networks to Remove Heavy Metal Ions from Water.

A variety of methods for removing heavy metal ions from wastewater have been developed but because of their low efficiency, further production of toxic sludge or other waste materials, high expense, and lengthy procedures, limited progress has been achieved to date. Polymeric hydrogel has been attracting particular attention for the effective removal of heavy metal ions from wastewater. Here, ionogenic polymeric hydrogels were prepared by free-radical copolymerization of a neutral acrylamide (AAm) monomer with an ionic comonomer in the presence of a suitable initiator and a cross-linker. Different types of ionic comonomers such as strongly acidic: 2-acrylamido-2-methylpropane sulfonic acid, weakly acidic: acrylic acid (AAc), and zwitterionic: 2-methacryloyloxy ethyl dimethyl-3-sulfopropyl ammonium hydroxide with varying amounts were incorporated into the poly(AAm) networks to fabricate the hydrogels. The heavy metal ions (Fe3+, Cr3+, and Hg2+) removal capacity of the fabricated hydrogels from an aqueous solution via electrostatic interactions, coordination bond formation, and a diffusion process was compared and contrasted. The poly(AAm) hydrogel containing weakly acidic AAc groups shows excellent removal capacity of heavy metal ions. The release and recovery of heavy metal ions from the hydrogel samples are also impressive. The compressive strength of hydrogels was found to be significantly high after incorporating heavy metal ions that will increase their potential applications in different sectors.

Facile strategy to construct a self-healing and biocompatible cellulose nanocomposite hydrogel via reversible acylhydrazone

Facile strategy to construct a cellulose nanocomposite hydrogel with self-healing and biocompatible properties is reported by crosslinking dialdehyde cellulose nanocrystals with acylhydrazine-terminated polyethylene glycol via dynamic reversible acylhydrazone for the first time. The effects of process variables on gelation time, mechanical strength and self-healing efficiency of hydrogels were investigated. It was found that gelation time shortened from hours to seconds by adjusting gelator and catalyst concentration. Tensile and compressive strength of hydrogel could reach 141 K Pa and 580 K Pa at 20.1% gelator concentration, respectively. Interestingly, the as-prepared hydrogel presented excellent self-healing ability without additional stimuli whose healing efficiency was higher than 90% even at higher gelator concentration. Furthermore, Cytotoxicity test showed that cell viability almost reached 100% after culturing with hydrogel, which revealed the hydrogel was biocompatible.

Preparation of Self-supporting Bagasse Cellulose Nanofibrils Hydrogels Induced by Zinc Ions.

Cellulose hydrogels are often prepared from native cellulose through a direct cellulose dissolution approach that often involves tedious process and solvent recovery problems. A self-supporting cellulose hydrogel was prepared by gelation of the TEMPO-oxidized bagasse cellulose nanofibrils (CNF) triggered by strong crosslinking between carboxylate groups and Zn2+. TEMPO process was used to generate negatively charged carboxylate groups on CNF surface to provide a high binding capability to Zn2+. Three TEMPO-oxidized CNFs of different carboxylate contents were prepared and characterized. TEM and AFM microscopes suggested that the sizes of CNFs were fined down and carboxylated cellulose nanofibrils (TOCNFs) of 5–10 nm wide, 200–500 nm long, and carboxylate contents 0.73–1.29 mmol/g were obtained. The final structures and compressive strength of hydrogels were primarily influenced by interfibril Zn2+-carboxylate interactions, following the order of TOCNFs concentration > content of carboxylate groups > concentration of zinc ions. A CO2 sensitive self-supporting cellulose hydrogel was developed as a colorimetric indicator of food spoilage for intelligent food packaging applications.

Hydrogels of chemically cross-linked and organ-metallic complexed interpenetrating PEG networks

The aim of the present work was to prepare a well-defined hydrogel of chemically cross-linked and organ-metallic complexed interpenetrating PEG networks. The hydrogel was synthesized via the reaction of copper(I)- catalyzed 1,3-dipolar azide-alkyne cycloaddition (CuAAC) with poly(ethylene glycol)-dopamine (PEG-DA) (“Click Chemistry”) followed by complexation with Fe3+ ions to crosslink the polymeric network. The chemical composition and morphology of the resulting hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), 1H-NMR and scanning electron microscopy (SEM). Swelling ratio, mechanical strength, conductivity, and degradation behaviors of the hydrogels were also studied. The effect of the polymer chain length on properties of hydrogels was explored. The compressive strength of hydrogels could reach as high as 13.1 MPa with a conductivity of 2.2 × 10-5 S·cm-1. The hydrogels also exhibited excellent thermal stability even at a temperature of 300 °C, whereas degradation of the hydrogel after 7 weeks was observed under a physiological condition. In addition, the hydrogel exhibited a good biocompatibility based on its in vivo performance through an in vivo subcutaneous implantation model. No inflammation and no obvious abnormality of the surrounding tissue were observed when the hydrogel was subcutaneously implanted for 2 weeks. This work is a step towards creating a new pathway to synthesize hydrogels of interpenetrating networks which could be of important applications in the future research.

Synthesis and properties of P(NIPAAm‐co‐AM)/SiO2 hybrid temperature‐sensitive hydrogels

AbstractUsing N, N′‐methylene bisacrylamide as crosslinking agent and potassium peroxydisulfate as initiator, the temperature‐sensitive hydrogels were prepared with organic monomer N‐isopropylacrylamide (NIPAAm) and acrylic amide and inorganic material ethyl orthosilicate (TEOS). The structure of hybrid hydrogels was represented by scanning electron microscopy and Fourier transform infrared spectroscopy. The volume phase transition temperature (VPTT) of hybrid hydrogels was determined by differential scanning calorimetry thermograms of the swollen hydrogel. The results showed that the VPTT of the hydrogels increased with the increasing of TEOS dosage. When the temperature was lower than VPTT, the hydrogels exhibited excellent temperature sensitivity and kept at a swelling state, but when the temperature was higher than VPTT, the hydrogels deswelled significantly. In addition, the compressive strength of hydrogels was studied, the results showed that hybrid hydrogels had more ideal mechanical properties than organic hydrogels. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013