Microstructure control of acrylic acid-styrenesulfonate copolymers for high-performance gypsum superplasticizers

This study is the first to investigate the synergistic effects of microstructure control in polymers composed of carboxylate (-COO^-) and sulfonate (-SO₃^-) groups for gypsum superplasticizers application. Polymers synthesized from acrylic acid (AA) and sodium 4-styrenesulfonate (SS) were prepared in diverse microstructures (homo, random, and block). Their performance as superplasticizers was systematically evaluated through fluidity and water reduction properties. While homo and random copolymers exhibited limited plasticization properties, block copolymers demonstrated superior performance due to the synergistic effects of the components and microstructure: the strong binding of PAA blocks onto the hemihydrate and the electrostatic and steric repulsion of PSS blocks. Block copolymer with longer PSS block exhibited stronger plasticization performance. This structural feature also effectively mitigated the adverse effects of AA on hydration kinetics (such as deceleration and reduced hydration) by increasing PSS:PAA ratio. As a result, block copolymers achieved a remarkable water reduction ratio up to 57.7 % compared to the neat calcium sulfate hemihydrate (CSH) slurry with a slight delay in hydration kinetics, improved workability and hydration extent. These findings emphasize the pivotal role of microstructure control through copolymer design providing valuable insights into the underlying mechanisms of advanced gypsum superplasticizers.