Construction of injectable starch-based superabsorbent resin with wet adhesion for agricultural application

Superabsorbent resins (SARs) have been developed to improve water management in agriculture. Injectable SARs offer significant potential for enhancing plant growth by penetrating deeply into the soil prior to gelation; however, relevant research remains scarce. In this study, injectable starch-based SARs were synthesised via a straightforward two-step process. Initially, hydrophilic polar groups were grafted onto the starch backbone, followed by crosslinking with pentaerythritol tris [3-(1-aziridinyl) propionate] (PTAP). This approach conferred both injectability and underwater gelation capabilities to the system. By adjusting the starch content, the time required for the gelation precursor to reach clogging and gelation points was significantly extended. Additionally, the effective injection ratio was enhanced, and macromolecular diffusion into water was inhibited, resulting in excellent injectability. The equilibrium swelling ratio of the resin reached 517.62 g/g with high water retention ratio. Because the contact angles of the gelation precursor on wood, glass, and aluminium surfaces were lower than those of water, it effectively displaced interfacial water, enabling strong underwater adhesion to the substrates. The gelation precursor effectively penetrated the crevices of wet sandstone and adhered the fragments without dispersal, highlighting its potential for applications in agricultural water retention and sandstone stabilisation.