Irradiation assisted synthesis of hydrogel: A Review

Hydrogels are crosslinked hydrophilic systems that can be made up of various routes. Radiation technology is one of the advanced routes explored for hydrogel synthesis. The gamma, electron beam, and microwave are the most extensively studied irradiation methods for hydrogel. The ionising radiations gamma and electron beam offer the benefit of synthesis and grafting without any initiator or crosslinker; hence, the highly pure product can be made and sterilisation can be achieved in a single step which is beneficial for medical applications. With a variation of the dosage of radiation, the gel content and swelling behaviour can be adjusted as these are the two prime properties. Both the gel fraction and swelling capacity increase up to a certain dosage and increasing the dosage further leads to a decrease in the performance due to compact structure formation, with more crosslinking points, and sometimes deterioration of properties in the case of natural polymers. Hence, optimization of radiation dosage is the crucial step. The nonionising radiation, namely microwave, is explored for the synthesis and it offers the benefit of better yield with faster reaction time. The radiation dosage studied for gamma is 0.5–50 KGy by varying the dose rate, whereas for electron beam, the dosage variation is mostly seen in the range of 10–50 KGy, whereas in few cases, 300 KGy is also studied and beam energy and beam current are another key parameter. By microwave, the power variation is done in the range of 100–800 W for the hydrogel synthesis.