From Vanillin to Concrete Plasticizers: An Innovative Path through ADMET Polymerization

Abstract

This study describes innovative lignin-based superplasticizers for concrete, focusing on two crucial features: (i) chelation capabilities (e.g., geminal diacids for binding with calcium ions), and (ii) repulsive methoxy polyethylene glycol (MPEG) chains (for better water solubility and particle repulsion). Starting from vanillin, the synthesis of the monomers relies on three key reactions: enzymatic dimerization, Williamson etherification, and Knoevenagel condensation. These monomers are then polymerized through acyclic diene metathesis (ADMET). The most effective polymer, chosen for its efficient polymerization and suitability for large-scale production, is modified to incorporate the desired functionalities and then tested in cement paste, showing deflocculation properties, with an adsorption rate of 42% (for a 35−40% purity range) and improved workability (≈85 Pa vs ≈130 Pa for pure paste). This approach opens up possibilities for further development, such as adjusting the MPEG chain length, MPEG-to-carboxylic acid ratio, molecular weight, and purification steps, to optimize the polymer's characteristics.