We use lignin’s surface activity to stabilize reverse (water-in-oil) emulsions through interfacial interactions with an organic, continuous phase containing polylactide (PLA). The rheological features of the emulsions are easily tailored to develop biobased coatings on hydrophilic substrates (glass or paper). Significantly, upon drying, the bicomponent coatings are shown for their uniformity and mechanical integrity at lignin loadings as high as 95% (with PLA being the balance). Compared to a commercial sunscreen, the PLA-lignin film templated from the emulsion is notably more effective in the UV-A region. Hence, UV-blocking (lignin) and water resistance (PLA) properties are combined in a system of practical relevance. Meanwhile, the transparency of the film is maintained. This work offers a novel and facile approach to achieving homogeneous lignin-based composite coating, further advancing this biomacromolecule as a substitute for non-renewable counterparts.
