Synthesis and Characterization of a Novel Lignin-Based Biopolymer from Ulex europaeus: A Preliminary Study

Abstract

Invasive plant species are a global environmental threat since they affect native species and can modify ecosystems, which negatively impacts human health and world economics. The aim of this preliminary study was to synthesize and characterize a new lignin-based biopolymer from gorse (Ulex europaeus), a globally widespread invasive plant. The lignin extraction was carried out through base/acid and solvent-based methodologies to compare the reaction yield. Subsequent polymerization of the extracted lignin was performed by glycine condensation in a 70% 1,4-dioxane solution with H2O2 and CaCl2 as catalysts. The extraction and polymerization products were characterized by Fourier-transform infrared spectroscopy. Thermal and stability properties of the new biopolymer were determined by thermogravimetric analysis, differential scanning calorimetry, and a soil burial test. The alkaline extraction process of lignin resulted in a higher yield than the process using an organic solvent. In comparison to the extracted lignin, the novel biopolymer showed different absorption bands that are characteristic of tensions and flexions of alkenes, amine, and amide groups. Additionally, thermal properties revealed peaks corresponding to decomposition and dehydration reactions, endothermic processes and a glass transition temperature of ≈259 °C. Potential biodegradation was observed. A new polymeric, possibly cross-linked, thermally stable material with a potentially high degree of crystallinity was synthesized from a renewable raw material, which might contribute to the gorse management according to the concept of novel ecosystem, as well as the reduction in contamination by other polymeric materials.