Fully biobased and biodegradable oxygen barrier coating for poly(lactic acid)†

Concerns regarding single-use petroleum-based plastic have led to a push toward bioplastic packaging. Poly(lactic acid) (PLA), one of the most utilized bioplastics, suffers from poor oxygen barrier that limits its application as a packaging material. In this work, layer-by-layer nanocoatings consisting of chitosan, deoxyribonucleic acid (DNA), and cellulose nanocrystals are applied to PLA to improve its barrier performance. These coatings decrease the oxygen transmission rate of PLA by up to 30× at just 120 nm of thickness, placing them among the best-performing fully biobased barriers ever reported. Combinations of coating materials are investigated to provide the best performance in both dry and humid conditions. The effect of humidity on the barrier performance is found to depend heavily on the presence of cellulose nanocrystals in the film. Additionally, the biobased coatings do not impede the biodegradability of the PLA substrate. The barrier technology and deposition process fulfill the principles of green chemistry and represent a significant improvement in sustainable gas barrier films.