New Dual Functional PHB-Grafted Lignin Copolymer: Synthesis, Mechanical Properties, and Biocompatibility Studies

Poly(3-hydroxybutyrate) (PHB) is a sustainable and biodegradable biopolymer from bacteria, but its brittle nature greatly limits its applications. In this study, we developed a lignin-PHB copolymer to enhance the mechanical properties of PHB. β-Butyrolactone was grafted onto the lignin core by using solvent-free ring-opening polymerization (ROP). Then different amounts of lignin-PHB copolymers were blended into PHB and then engineered into nanofibers via electrospinning. The composite nanofibers with lignin-PHB copolymer exhibit much stronger mechanical properties than pure PHB fibers. Composite nanofibers with 2% lignin copolymer demonstrate the best mechanical performance with tensile strength increasing from 1.45 ± 0.36 MPa to 5.61 ± 0.63 MPa, Young's modulus increasing from 54.7 ± 1.2 MPa to 84.6 ± 10.0 MPa, and elongation increasing from 9.6 ± 2.2% to 93.5 ± 7.6%. Moreover, PHB/lignin nanofibers demonstrate tunable antioxidant activity, allowing the neutralization of excess free radicals in our body. Animal studies also demonstrate that the PHB/lignin nanofibers are nonirritating and biocompatible. Hence, these new PHB/lignin nanofibers hold great potential for biomedical applications.