Solvent-Driven Interfacial Regulation of Lignin/PCL Composites Using γ-Valerolactone

Abstract

The intrinsic incompatibility between lignin and biodegradable polyesters remains a key barrier to the development of high-performance biobased composite films. We propose a γ-valerolactone (GVL)-enabled strategy to regulate interfacial interactions between alkali lignin (AL) and polycaprolactone (PCL) through cross-linking network formation. GVL serves as a dissolution and purification medium, removing insoluble impurities and aggregates while promoting homogeneous lignin dispersion. A flexible cross-linked network is constructed via epoxy ring-opening reactions, enhancing interfacial adhesion and modulating chain mobility. The resulting films exhibit balanced mechanical strength (14.64 MPa) and ductility (1415% elongation), together with ultraviolet shielding, photothermal conversion (∼25 °C), and tunable gas/water vapor transport (O2/CO2 ≈ 1.2; WVTR < 100 g/(m2·day)). This study provides fundamental insights and a scalable pathway for engineering biodegradable composite films.