Biobased Films from Amphiphilic Lignin-Graft-PLGA Copolymer

Amphiphilic copolymers were synthesized by grafting poly(lactic-coglycolic) acid with two lignin types: alkaline lignin and lignosulfonate. An interphase formation technique was used to produce films based on the copolymers. Films presented one side as being more hydrophobic (Oside) and smoother, and the second side more polar and with an uneven surface (W-side). Contact angle of water on the W-side was lower than the O-side corresponding to a higher lignin content and influenced by the lignin type (alkaline < lignosulfonate) and lignin: PLGA ratio. X-ray photoelectric spectroscopy analysis showed higher percentages of sulfur on the W-side, which supports a preferential partitioning of the lignin. Tensile testing demonstrated the significant impact of lignin type on the mechanical properties of the films. Alkaline films showed a higher maximum strength, a higher stiffness, and a higher tensile strength at the elastic limit compared to lignosulfonate films. However, for lignosulfonate films, ductility at break point was 4-fold higher than that of alkaline films.