Biobased films from amphiphilic lignin-graft-PLGA copolymer

Amphiphilic copolymers were synthesized by grafting poly(lactic-co-glycolic) 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 (O-side) 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.