A method of forming a crosslinked polyphenol, the method comprising: reacting a bio-based phenolic compound comprising at least one phenolic hydroxyl group, with a crosslinking agent comprising at least two functional groups reactive with the phenolic hydroxyl group, wherein the at least two functional groups are each independently a halogen group, acid halide group, sulfonyl halide group, glycidyl group, anhydride group, or a combination comprising at least one of the foregoing, to provide the crosslinked polyphenol.