Biobased Acids in Production of Hybrid Superabsorbent Polymer Hydrogels: A Review

In recent years, hydrogels have been considered as one of the most promising materials due to their unique properties. Hydrogels are cross-linked hydrophilic polymer structures that are able to absorb and holding water or biological fluid. Thus, the hydrogel networks can extensively swell in water media without dissolution. In the last few decades, hydrogels been used in various industries such as food, packaging, pharmaceuticals and drug delivery systems, agriculture, biomedical and bioengineering applications, manufacturing of technical and electronic devices, and as adsorbents for the removal of pollutants in environmental applications. Superabsorbent polymer (SAP) hydrogels are a type of hydrogel that, due to the hydrophilic nature of polymer chains can absorb and retain extraordinary large amounts of water or aqueous solution up to hundreds of times their weight. In recent years, , new superabsorbent hydrogels have been developed for different applications. High demand for these substances, especially in personal hygiene, has led to an increase in their production (now over three million tons per year). Because the main components of commercial and widely used SAPs in industry are based on raw materials derived from fossil resources (oil, gas and coal), the widespread use of SAPs and their increasing production, on the one hand, have contributed to environmental concerns by contributing to water, soil and air pollution, and, on the other hand, have threatened global price fluctuations and the degradability of fossil resources. Therefore, the replacement of at least some components of SAPs with natural, biobased or renewable raw materials (such as lactic acid, succinic acid and itaconic acid) and the production of SAPs with hybrid structures have been considered. The purpose of this paper is to review the hybrid SAPs based on some biobased compounds that are used in three structural parts of the polymer network including crosslinker, surface modifier and monomer.