Silane-mediated network formation in chitosan: Viscoelasticity, porosity, and gravity-driven selective water transport with broad-spectrum antibacterial activity.

Chitosan gels possess intrinsic hydrophilicity, biocompatibility, and antibacterial characteristics, but their practical use in aqueous separation is often limited by insufficient network stability and the difficulty of combining mechanical integrity with dynamic functionality. In this work, a 3-Aminopropyltriethoxysilane (APTES) mediated chitosan gel was designed by introducing hydrolysable silane functionality into the chitosan network to construct an organic-inorganic architecture with interconnected dynamic interactions. The resulting network architecture altered the viscoelastic response, swelling behavior, thermal resistance, and interfacial properties of the chitosan matrix. Among the investigated formulations, CS-APTES-1 showed a predominantly elastic response (G' > G″), high swelling at pH 4 (1318%), and improved thermal robustness. More importantly, the combination of pronounced surface hydrophilicity (water contact angle, 8.1°) and poor wetting by hexane (119.1°) translated the molecular network modification into selective macroscopic transport: water was rapidly absorbed from hexane-water mixtures and separated under gravity without externally applied pressure. The material also retained the self-healing characteristic of the network and exhibited concentration-dependent antibacterial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Klebsiella pneumoniae. These findings show that silane incorporation couples chitosan's structural and interfacial characteristics with dynamic healing and selective liquid transport, rather than serving merely as a compositional crosslinking modifier. The resulting architecture offers a chitosan-based platform for passive water-selective separation.