Preparation and properties of ionic crosslinked nanocomposite high strength hydrogel

A high-performance ion crosslinked nanocomposite hydrogel was successfully synthesized by integrating free radical polymerization with salt solution immersion. Initially, halloysite nanotubes (HNTs) were modified with water-soluble short chain chitosan (CS), followed by the formation of the nanocomposite hydrogel matrix through thermal initiated radical polymerization with acrylamide (AM), acrylic acid (AA), and other components. Subsequently, soaking the hydrogel in Fe (NO₃)₃ and Na₂SO₄ solutions resulted in the formation of an ion crosslinked nanocomposite hydrogel with superior mechanical properties, unique anti-swelling characteristics, and frost resistance. FTIR and TEM analyses confirmed the formation of the HNTs @CS structure. SEM observations of the composite hydrogel revealed a more compact structure and significantly reduced pore size post-ion immersion. The impact of varying AA and HNTs contents on the mechanical properties of the composite hydrogels was investigated. Optimal results are obtained when CS is 2 wt%, AA accounts for 12 mol% of the total monomer, AM accounts for 88 mol%, HNTs is 3.5 wt%, and immersion in Fe³⁺ and \textSO_4^2- ion solutions, yielding the best comprehensive mechanical properties with a tensile strength of 3.96 MPa, elongation at break of 553%, and compressive strength of 13.4 MPa at 85% strain. Following a 48-hour deionized water soaking period, the tensile strength increases to 5.64 MPa, and the modulus reaches 15 MPa, showcasing a new strategy for the design and development of robust and resilient hydrogels.