Lignin-based nanoparticles hold tremendous potential for various applications. This study proposes an innovative and straightforward method for the synthesis of spherical hybrid lignin nanoparticles (hy-LNPs) with a tunable pore structure. The approach involves blending lignin with 20wt% polyamide-epichlorohydrin, resulting in the formation of thermoresponsive lignin-based polyelectrolyte complexes. Upon heating to 80°C, the complexes undergo self-assembly into uniform spherical nanoparticles, achieving a minimum polydispersity index (PDI) as low as 0.08. The study reveals that nanoparticle formation involves simultaneous collapse and growth. During collapse, hy-LNPs become more compact, increasing their elastic behavior and inhibiting particle coalescence, which is critical for the formation of stable, low-dispersibility nanoparticles. Contrary to the expectation that collapse would reduce pore size, the average pore size of the hy-LNPs increases from 24.9nm to 35.8nm, likely due to the coalescence of smaller pores into larger ones. Furthermore, this straightforward method was applied to encapsulation β-cypermethrin, achieving an encapsulation efficiency of up to 95% and reducing the release rate in an ethanol-water solution from 90.6% to 63.1% over 5h. The thermoresponsive lignin-based polyelectrolyte complexes provide a new pathway for the controlled preparation of lignin-based nanoparticles. These nanoparticles demonstrate promising potential for applications such as drug encapsulation.
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