Fabrication of Hydrophobic\nLignin-Based Films through\nTandem Chemical Modification and Plasma Treatment

Fully renewable hydrophobic materials offer a promising\nsolution\nto addressing environmental challenges. Lignin, a relatively underutilized\nrenewable polymer that naturally exhibits hydrophobicity, shows potential\nas a blend material in various applications. However, current approaches\nusing technical lignin as a primary component or additive in renewable\nfilm manufacturing often rely on nonrenewable, external hydrophobic\nagents. Here, we developed a tandem strategy to create a fully renewable,\nhydrophobic lignin-based film. First, lignin was esterified by incorporating\nlong-chain palmitic groups to enhance its hydrophobicity. A poly[(<i>R</i>)-3-hydroxybutyrate] (PHB) film containing 20% palmitoylated\nlignin demonstrated improved hydrophobicity, with the water contact\nangle (WCA) increasing from 75.4 to 106.7°. To further enhance\nhydrophobicity, the film underwent oxygen plasma treatment, which\nintroduced macroscopic surface roughness in the form of “nanoforests.”\nThis treatment significantly increased the WCA to 139°, confirming\nthe effectiveness of the tandem strategy for producing hydrophobic\n2D materials. Molecular dynamics simulations revealed that the C16\nchain in palmitoylated lignin created a more compact complex with\nPHB through strong van der Waals interactions and optimized hydrogen\nbonding, suggesting potential for developing high-lignin-content films.\nThis work demonstrates a facile approach for fabricating fully renewable,\nhydrophobic composite films without the need for external materials.