The cross-linking density of polymer-based superabsorbent materials has a significant impact on their water absorbency and swelling behavior. Cross-linking refers to the formation of chemical bonds between polymer chains, creating a three-dimensional network structure. The cross-linking density is the number of cross-links per unit volume of the polymer network.1. Effect on water absorbency: As the cross-linking density increases, the water absorbency of the superabsorbent material generally decreases. This is because a higher cross-linking density leads to a more rigid and compact polymer network, which restricts the movement of polymer chains and reduces the space available for water molecules to penetrate and be absorbed. Conversely, a lower cross-linking density results in a more flexible and open network, allowing for greater water absorption.2. Effect on swelling behavior: The swelling behavior of superabsorbent materials is also influenced by the cross-linking density. A higher cross-linking density leads to a lower degree of swelling, as the rigid and compact network structure restricts the expansion of the polymer chains upon water absorption. On the other hand, a lower cross-linking density allows for greater swelling, as the more flexible and open network can accommodate the expansion of polymer chains more easily.In summary, varying the cross-linking density of polymer-based superabsorbent materials can significantly affect their water absorbency and swelling behavior. A higher cross-linking density generally results in lower water absorbency and swelling, while a lower cross-linking density leads to higher water absorbency and swelling. However, it is essential to strike a balance between the cross-linking density and the desired properties of the superabsorbent material, as extremely low cross-linking densities may lead to weak mechanical properties and poor stability.