Lignin (isolated lignin and commercial lignin) was initially dissolved with 90% DMSO and this solution was incorporated into
the film solution at different concentrations (1, 2, 3, 4 and 5% v/w of film forming solution). Subsequently, the solution was heated in a hot water bath (at 85 C) under constant magnetic stirring (at 350 rpm for 45 min) and the resulting solution was cooled to room temperature