Superabsorbent

Abstract

Superabsorbent hydrogel (SAH) is a cross-linked polyelectrolyte polymer that has the capability to absorb a lot of water by keeping it in a three-dimensional (3D) structure. The network’s structure of SAH has the high elasticity that gives the ability of pores to expand in an aqueous media into up to 150–1500 times their own size in a dry state. The size of pores is the major factor that controls the swelling degree of the hydrogel. In contrast, the swelling degree is related to cross-linked density and the number of polarizable functional groups that immobilize on the polymer backbone. The hydrogels could be made by radical-initiated polymerization of hydrophilic monomers, and/or linear polymers dissolve in an aqueous solution. Free radical polymerization of the hydrogel can be done physically or chemically. Advantages and disadvantages of each method will be elabo-rated in this chapter. The advances in radiation cross-linking methods for the hydrogel preparation are particularly addressed besides other different techniques, e.g., (freezing/ thawing and chemical initiation). This chapter will review the preparation methods of superabsorbent hydrogels from synthetic and natural hydrophilic polymers with other new phases such as wax, gum, and rubber. Methods to characterize these hydrogels and their proposed applications (internal curing agent for cement, agricultural proposal, biomedical proposal, and environmental proposal) are also reviewed.