Intelligent response organo-montmorillonite/Fe3+-alginate/poly (N-isopropylacrylamide) interpenetrating network composite hydrogels for controlled release of water-insoluble pesticides

Enclosing the pesticide in a carrier and releasing it based on environmental stimuli is proved to be a viable strategy for addressing pesticide losses and mitigating environmental contamination. Here, an interpenetrating network (IPN) composite hydrogels (OMt/Alg/PNIPAm) with light and temperature responses was prepared by the incorporation of clay material, organo-montmorillonite (OMt), via the free-radical polymerization of Nisopropyl acrylamide (PNIPAm) and its crosslinking as well as ionic crosslinking reaction of sodium alginate (SA) with FeCl3. The structure of OMt/Alg/PNIPAm was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermos gravimetric analysis (TGA) and rheometer. The hydrophobic pesticide lambda-cyhalothrin (LC) was encapsulated in OMt and subsequently incorporated into the IPN structure of the composite hydrogels, ensuring the desirable mechanical properties, encapsulation efficiency and sustained release performances of the composite hydrogels. In addition, with the rising of OMt content, the IPN composite hydrogels exhibited a decrease in their swelling capacity, transparency, and temperature sensitivity. The OMt/Alg/PNIPAm with 9.0% OMt content displayed the highest loading rate for pesticides at 82.06% and the lowest release rate of pesticides at 3.90%. Furthermore, the IPN composite hydrogels possessed the ability to regulate the amount of pesticide release based on the variations in temperature and ambient light conditions. The resultant IPN composite hydrogels took advantage of the temperature responsiveness of PNIPAm, the light sensitivity of Fe3+-alginate hydrogel, and the adsorption capability of OMt, possessing great potentials in enhancing the utilization efficiency of hydrophobic pesticides through the development of effective and eco-friendly pesticide formulations.