A bio-based adhesive composed of polyelectrolyte complexes of lignosulfonate and cationic polyelectrolytes

Polyelectrolyte complexes composed of lignosulfonate and cationic polyelectrolytes were used as bio-based adhesives. Sodium lignosulfonate (L-SO₃Na), a wood-derived anionic polyelectrolyte, was combined with three different cationic polyelectrolytes and the adhesive strength of the resulting complexes was evaluated on various substrates. Higher adhesive strength was observed with polar substrates (stainless steel, aluminum, and wood) compared to a nonpolar substrate (polypropylene). Complexes L-SO₃Na/poly(allylamine) and L-SO₃Na/ε-poly-l-lysine exhibited higher adhesive strength than the other polyelectrolyte complexes on aluminum and a commercial polyvinyl acetate adhesive on wood. In addition, our adhesives do not require any additional chemical reagents, such as organic solvents, crosslinkers, or condensation agents. The L-SO₃Na/ε-poly-l-lysine complex is a strong and completely biodegradable adhesive. This study demonstrates the use of lignosulfonate in the development of low-toxicity, sustainable, and biodegradable adhesives with excellent adhesive strength.