Preparation and properties of UV-absorbent lignin graft copolymer films from lignocellulosic butanol residue

The aim of this study was to develop economically UV-absorbent and visible-transparent films. For this purpose, lignin was selected because of its strong ultraviolet (UV) absorbing property. Lignocellulosic butanol residue, as the by-product of lignocellulosic butanol production, is rich in biobutanol lignin (BBL). Herein, BBL was modified with acryloyl chloride and then copolymerized with n-butyl acrylate (BA) and methyl methacrylate (MMA) by free-radical polymerization. The chemical structure of poly(BA-co-MMA) chains was identifiable by 1 H NMR and 13 C NMR spectroscopies, combined with UV–visible spectra to confirm the existence of the aromatic groups that are attributed to BBL in the copolymer . This provided evidence that a BBL graft copolymer was successfully synthesized. The optical, photo-stability, chemical resistance, thermal and mechanical properties of the copolymer were evaluated. The copolymer film can absorb 96.2% of UV light, while allowing 70% or higher transmittance in the visible spectrum when the surface concentration of BBL-AC was 240   μg   cm −2 . In addition, the copolymer film retained excellent absorption capacity in the UV region and high transparency in the visible light region after 75   min continuous UV-irradiation or when heated at 100   °C, rendering it potential to use as a UV-absorbent film. The copolymer exhibited good chemical resistance, thermal and mechanical properties compared with pure poly(BA-co-MMA). This strategy not only provides a novel approach for UV-absorbent films but also greatly extends the comprehensive utilization of BBL.