Fundamental Concepts of Hydrogels: Synthesis, Properties, and Their Applications

Abstract

In the present review, we focused on the fundamental concepts of hydrogels—classification, the polymers involved, synthesis methods, types of hydrogels, properties, and applications of the hydrogel. Hydrogels can be synthesized from natural polymers, synthetic polymers, polymerizable synthetic monomers, and a combination of natural and synthetic polymers. Synthesis of hydrogels involves physical, chemical, and hybrid bonding. The bonding is formed via different routes, such as solution casting, solution mixing, bulk polymerization, free radical mechanism, radiation method, and interpenetrating network formation. The synthesized hydrogels have significant properties, such as mechanical strength, biocompatibility, biodegradability, swellability, and stimuli sensitivity. These properties are substantial for electrochemical and biomedical applications. Furthermore, this review emphasizes flexible and self-healable hydrogels as electrolytes for energy storage and energy conversion applications. Insufficient adhesiveness (less interfacial interaction) between electrodes and electrolytes and mechanical strength pose serious challenges, such as delamination of the supercapacitors, batteries, and solar cells. Owing to smart and aqueous hydrogels, robust mechanical strength, adhesiveness, stretchability, strain sensitivity, and self-healability are the critical factors that can identify the reliability and robustness of the energy storage and conversion devices. These devices are highly efficient and convenient for smart, light-weight, foldable electronics and modern pollution-free transportation in the current decade.

Recent Progress in Polysaccharide Aerogels: Their Synthesis, Application, and Future Outlook

“…Various factors such as the type of cross-linking process (physical or chemical) must be considered along with the relevant conditions of temperature, pH, concentration, functional group, solvent, and cross-linker composition. A crosslinked aerogel polymer can be built by simple mixing, solution casting, free radical polymerization, ultraviolet (UV) and gamma ray irradiation, bulk polymerization, or interpenetration [ 74 ]. To improve the physicochemical properties of the polysaccharides, the availability of the functional groups should be increased.…”

Elucidating the Molecular Mechanisms for the Interaction of Water with Polyethylene Glycol-Based Hydrogels: Influence of Ionic Strength and Gel Network Structure

“…Hydrogels ( Figure S1A ) have widespread applications in many fields such as biomaterials, drug delivery, tissue engineering, soft robotics, soft electronics and sensors [ 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. Hydrogels can be classified in a number of ways, according to their source, composition, and properties [ 10 ]. The polymer source is either natural or synthetic.…”

Light and Hydrogels: A New Generation of Antimicrobial Materials

“…Among all the most efficient described strategies, hydrogels have been considered as excellent candidates for effective antibacterial applications. Hydrogels are a class of soft polymeric materials that have been playing a significant role in numerous fields since they first came to light in the mid-20th century [ 34 , 35 , 36 ]. Briefly, hydrogels are a hydrophilic three-dimensionally crosslinked polymeric network.…”

“…Briefly, hydrogels are a hydrophilic three-dimensionally crosslinked polymeric network. They are obtained through gelation, a process that occurs when water-soluble monomeric units and polymeric chains physically or chemically crosslink together to form a non-soluble 3D porous structure [ 34 , 35 , 36 , 37 ]. One of their main characteristics is their ability to retain a substantial amount of water in their swollen state because of hydrophilic entities such as hydroxyl, amino, ether or carboxylic groups in their polymeric chains while being insoluble in water.…”

“…Hydrogels have been exhaustively described in the literature by several outstanding reviews [ 34 , 35 , 36 , 37 , 38 ]. They are broadly classified into many subtypes based on:…”