Enhanced water vapor barrier properties for biopolymer films by polyelectrolyte multilayer and atomic layer deposited Al_2O_3 double-coating

摘要

Commercial polylactide (PLA) films are coated with a thin (20 nm) non-toxic polyelectrolyte multilayer (PEM) film made from sodium alginate and chitosan and additionally with a 25-nm thick atomic layer deposited (ALD) Al_2O_3 layer. The double-coating of PEM + Al_2O_3 is found to significantly enhance the water vapor barrier properties of the PLA film. The improvement is essentially larger compared with the case the PLA film being just coated with an ALD-grown Al_2O_3 layer. The enhanced water vapor barrier characteristics of the PEM + Al_2O_3 double-coated PLA films are attributed to the increased hydrophobicity of the surface of these films.