Conformation and Adsorption Properties in Aqueous Solution for Polycarboxylate Superplasticizers with Different Main Chain Lengths

The conformation in aqueous solution and the adsorption ability to water molecules of polycarboxylate ether (PCE) superplasticizer have important effects on its the properties. In this work, molecular dynamics (MD) simulations were employed to investigate the conformation of PCE molecules and the interaction between PCE and water molecules at microscopic level. Five kinds of PCE molecular models (PCE-2, PCE-6, PCE-10, PCE-14 and PCE-18) with different lengths of main chain were constructed, and the simulation results show that the longer length of main chain makes PCE molecules more stretched. The steric hindrance of PCE enhances from PCE-2 to PCE-14, and then declines from PCE-14 to PCE-18, which result from the greater molecules aggregation. The radial distribution functions (RDFs) indicate that the water absorption capacity of PCE molecule enhanced with the increasing of main chain length, and main chain plays an important role of water molecule capture. Both steric hindrance and water absorption capacity of PCE molecules can effectively affect the diffusion properties of water molecules, and prevent water molecules from contacting with cement particles, which retards the hydration process of cement.