Analysis of responsive characteristics of ionic-strength-sensitive hydrogel with consideration of effect of equilibrium constant by a chemo-electro-mechanical model

Rice straw derived cellulose-based hydrogels synthesis and applications as water reservoir system

This study synthesized new cellulose-based hydrogels, namely cellulose and cellulose/poly acrylic acid, using cellulose extracted from rice straw via alkaline and acidic pulping processes. The research demonstrated alkaline treatment with sodium hydroxide to be more effective for cellulose extraction compared to acidic treatment. Hydrogel synthesis used graft polymerization and chemical crosslinking with potassium persulfate as initiator and epichlorohydrin as a crosslinker. Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TG), and scanning electron microscopy (SEM) characterized the prepared hydrogels. Important factors determining hydrogel competence are swelling ratio and water retention rate. The cellulose hydrogel exhibited the highest swelling ratio in tap water (9811%) with 76.25 wt% water retention and in artificial hard water (3121.43%) with 64.58 wt% retention after 4 days outdoors at 298 K. Finally, hydrogels were investigated extensively for agricultural applications. Fenugreek seeds germinated and grew well (67% germination after 7 days) in normal soil mixed with 10% cellulose hydrogel. Biodegradability testing exhibited 6% degradation after 40 days and 10% after 120 days in an open-air lab at room temperature and 60% humidity.

Cellulose-based hydrogel materials: chemistry, properties and their prospective applications

Hydrogels based on cellulose comprising many organic biopolymers including cellulose, chitin, and chitosan are the hydrophilic material, which can absorb and retain a huge proportion of water in the interstitial sites of their structures. These polymers feature many amazing properties such as responsiveness to pH, time, temperature, chemical species and biological conditions besides a very high-water absorption capacity. Biopolymer hydrogels can be manipulated and crafted for numerous applications leading to a tremendous boom in research during recent times in scientific communities. With the growing environmental concerns and an emergent demand, researchers throughout the globe are concentrating particularly on naturally derived hydrogels due to their biocompatibility, biodegradability and abundance. Cellulose-based hydrogels are considered as useful biocompatible materials to be used in medical devices to treat, augment or replace any tissue, organ, or help function of the body. These hydrogels also hold a great promise for applications in agricultural activity, as smart materials and some other useful industrial purposes. This review offers an overview of the recent and contemporary research regarding physiochemical properties of cellulose-based hydrogels along with their applications in multidisciplinary areas including biomedical fields such as drug delivery, tissue engineering and wound healing, healthcare and hygienic products as well as in agriculture, textiles and industrial applications as smart materials.

Polysaccharides based superabsorbent hydrogel from Linseed: Dynamic swelling, stimuli responsive on-off switching and drug release

Swelling properties of Linseed hydrogel (LSH) were studied in deionized water and different physiological pH values, i.e., 1.2, 6.8 and 7.4. Analysis of the kinetics drawn from swelling data has revealed that swelling of LSH followed second order kinetics. The results indicated that swelling of LSH is greatly affected by different concentration of salts. Stimuli responsive on-off switching of LSH was studied in water/normal saline, water/ethanol and basic/acidic environment and found reversible. LSH swells maximum in water and at pH 7.4 while deswells abruptly in ethanol and at pH 1.2. The elongated porous structures uniformly organized in layers were observed in FE-SEM. LSH was used as a sustained release material for tablet formulation of diclofenac sodium. Drug release study followed non-Fickian diffusion. LSH sustained the release of drug even better than a commercially available formulation of diclofenac sodium.

Redox-responsive organometallic hydrogels for in situ metal nanoparticle synthesis

A new class of redox active hydrogels composed of poly(ferrocenylsilane) polyanion and poly(ethylene glycol) chains was assembled, using a copper-free azide-alkyne Huisgen cycloaddition reaction. These organometallic hydrogels displayed reversible collapse and reswelling upon chemical oxidation and reduction, respectively, and formed relatively well-defined, unaggregated Pd(0) nanoparticles (8.2 ± 2.2 nm) from K2PdCl4 salts.

Stimulus-responsive polymers and other functional polymer surfaces as components in glass microfluidic channels

The integration of smart stimulus-responsive polymers as functional elements within microfluidic devices has greatly improved the performance capabilities of controlled fluid delivery. For their use as actuators in microfluidic systems, reversible expansion and shrinking are unique mechanisms which can be utilized as both passive and active fluid control elements to establish gate and valve functions (passive) and pumping elements (active). Various constituents in microfluidic glass channels based on stimulus-responsive elements have been reported based on pH-responsive, thermoresponsive and photoresponsive coatings. Fluid control and robust performance have been demonstrated in microfluidic devices in a number of studies. Here we give a brief overview of selected examples from the literature reporting on the use of stimulus response polymers as active or passive elements for fluid control in microfluidic devices, with specific emphasis on glass-based devices. The remaining challenges include improving switching times and achieving local addressability of the responsive constituent. We envisage tackling these challenges by utilizing redox-responsive polymers which offer fast and reversible switching and local addressability in combination with nanofabricated electrodes.

Transient modeling for kinetic swelling/deswelling of the ionic-strength-sensitive hydrogel

The multi-effect-coupling ionic-strength-stimulus (MECis) model is presented for transient simulation of the kinetic deformation behavior of the ionic-strength-sensitive hydrogel, based on the laws of conservation of mass and momentum, where the chemical, electrical and mechanical effects are considered on the kinetics of the hydrogel. The simulated kinetic swelling/shrinking characteristics by the MECis model are compared with the experiments. It is concluded that the model is able to predict well the responsive variation of the ionic-strength-sensitive hydrogel with time.