Synthesis, Performance Evaluation, and Adsorption–Dispersion Mechanism of Sulfonic Acid-Terminated Long Side Chain Polycarboxylate Superplasticizers

Polycarboxylate superplasticizers (PCEs) achieve dispersion mainly via steric hindrance from poly­(ether) side chains. However, long side chains may cause structural collapse. This study mitigates this issue by introducing sulfonic acid terminations to the long side chains, synthesizing sulfonic-terminated polycarboxylates (PCEPS). Electrostatic repulsion between sulfonic and carboxyl groups on the main chain reduces the level of collapse, enhancing PCE dispersion in cement. PCEPS-4000 showed the strongest dispersion compared with conventional PCEs (PCEC). PCEPS-4000 formed an adsorption layer thickness (ALT) of 11.65 nm, showing a significant improvement over the 7.93 nm observed in the carboxyl-terminated long side chain polycarboxylate (PCETA). Stronger negative charge and lower complexation of sulfonic acid groups enhance the side chain extension. PCEPS also shows good clay tolerance and slump retention, proving its versatility as a concrete admixture.