Effects of structure on the properties of low-molecular-weight superplasticizer using phosphonate as the adsorption group

Two types of low-molecular-weight superplasticizers using phosphonate as the adsorption group were synthesized in one pot by the Moedrizer-Irani procedure from the single amino-terminated or the double amino-terminated polyethers. Results of cement paste test indicated that single bis(phosphonic acid)amino-terminated polymers (polymer of type A) exhibited good water-reducing ability, while double bis(phosphonic acid)amino-terminated polymers (polymers of type B) showed good fluidity-maintaining abilities and had a longer setting time. Adsorption isotherms indicated that polyether chains of polymer of type B might curl up on the surface of cement particle or form a chelated structure with Ca2+ in aqueous phase, which restricted the effect of steric hindrance. And the adsorption layer thickness of polymer M1 was calculated as 0.46 nm through X-ray photoelectron spectroscopy test, while which of polymer M3 was 0.89 nm. Furthermore, cement hydration test and SEM were also used to reveal the effects of structure on the properties of the two different kinds of polymers. These useful information provide the potential to explore new kind of superplasticizers in the future.