Lignin-based nanogels for the release of payloads in alkaline conditions

Bio-based nanoparticles are promising materials in agriculture because they enable a controlled release of agrochemicals to plants. The release can be more specific by engineering nanoparticles with stimuli-responsive properties. Herein, we reported lignin-based nanogels which can release payloads in alkaline conditions. Lignin methacrylate was emulsified in miniemulsion droplets and graft copolymerized with acrylic acid to form core-shell nanogels. The successful incorporation of acrylic acid and lignin units in the nanogels was confirmed by FT-IR, H-NMR and XPS spectroscopies. TEM and dynamic light scattering analysis demonstrated that the nanogels were spherical and uniformly dispersed in the aqueous phase. AFM nanoindentation and thermal analysis indicated that the nanogels were mechanically and thermally durable. Lignin-based nanogels exhibited a pH-responsive swelling at high amounts of acrylic acid. Various hydrophobic payloads were encapsulated in high yield and could be preferentially released in alkaline conditions. Lignin-based nanogels are therefore the potential nanocarrier for the controlled release of agrochemicals such as pesticides or fungicides.