Characterisation of pineapple leaf fibre/poly(methacrylic acid) semi-interpenetrating network hydrogel

• A novel PALF/PMAA semi-IPN hydrogel was developed via hydrogen bonding between their functional groups. • Optimal PALF/PMAA hydrogel formulation was identified by varying MAA concentrations. • PALF addition enhanced swelling and mechanical properties of semi-IPN hydrogels. • Morphology analysis confirmed –OH (PALF) and –COOH (PMAA) interactions absent in pure PMAA. • Renewable semi-IPN hydrogels show potential for biomedical and environmental applications. This work presented a novel semi-interpenetrating (semi-IPN) hydrogel of a poly(methacrylic acid) (PMAA) matrix by incorporating pineapple leaf fibre (PALF). The reinforcement significantly enhanced its mechanical properties, thermal stability, and pH-responsive swelling behavior. FTIR confirmed the strong intermolecular interactions between PALF and PMAA while TGA and XRD show enhanced crosslinking and crystallinity with a cellulose I peak at 2θ = 22.5° and a crystallinity index of 86.07 %. At pH 7, the hydrogel expanded 2.3 times, demonstrating pH-sensitive swelling as well. Dynamic mechanical analysis (DMA) revealed the highest storage modulus (E’ = 5.50 MPa), damping factor (tan δ = 0.33), and glass transition temperature (Tg = 100 °C) of PALF/PMAA semi-IPN2 confirming its good energy dissipation, and high stiffness. Conversely to pure PMAA hydrogels, the optimised PALF/PMAA hydrogel exhibited a significantly greater compressive strength and Young’ Modulus of 184.80 and 26.30 MPa, respectively. SEM imaging verified that PALF was uniformly distributed and had porous shape, both of which enhanced the mechanical characteristics. This is the first study to use PALF as a reinforcing agent in PMAA-based hydrogels, creating a strong, pH-responsive material with great potential for biomedical, environmental, and drug delivery applications.