Biodegradable multilayer barrier films based on alginate/polyethyleneimine and biaxially oriented poly(lactic acid)

► Biodegradable multilayer films were prepared based on alginate and BOPLA. ► The oxygen barrier of the ALG/PEI coated BOPLA film was significantly improved. ► WVP, tensile properties and optical clarity were also studied. ► A possible barrier mechanism was proposed. A layer-by-layer (LBL) approach was used to assemble alternating layers of sodium alginate (ALG)/polyethyleneimine (PEI) on biaxially oriented poly(lactic acid) (BOPLA) films in order to produce bio-based all-polymer thin films with low gas permeability. Increasing the depositing of ALG and PEI from 0 to 30 layers results in large thickness variations (from 0 to 3.92μm). After 30 ALG/PEI layers are deposited, the resulting assembly has an OTR of 1.22cm3/(m2dayatm). When multiplied by thickness, the resulting oxygen permeability (OP) is found to be less than 3.8×10−17cm3cm/cm2sPa, which is almost 3 orders of magnitude lower than that of uncoated BOPLA film (1.8×10−14cm3cm/cm2sPa). At the same time, the resulting multilayer-coated BOPLA films maintain high optical clarity and tensile properties. This unique barrier thin film has become a promising alternative to non-biodegradable synthetic food packaging materials.