Preparation of bio-based styrene alternatives and their free radical polymerization

Three different bio-based styrene monomer alternatives, i.e., 4-vinylphenol derivatives, were synthesized starting from lignin building blocks. The synthetic route encompassed a green Knoevenagel condensation followed by two decarboxylation steps and acetylation. High isolated yields for the decarboxylation were obtained in a polar aprotic solvent, which prevented oligomerization. The polymerization of the three acetylated 4-vinylphenols was performed by free radical polymerization. The chain transfer constants of styrene and 4-acetoxy styrene 4c in toluene were evaluated in the Mayo procedure using the number-average molecular weight (Mn). After polymerization, the acetoxy group of the different polymers was efficiently hydrolyzed. The resulting phenol side groups of these polystyrene alternatives provide future opportunities to functionalize these bio-based polymers further.