Water-soluble copolymers of methoxy polyethylene glycol acrylate (mPEGA) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were synthesized by free radicalic polymerization and evaluated as slump-retaining dispersant for cement particles. The slump-retaining effect of the synthesized copolymers was studied in terms of reaction pH, composition, and molecular weight of mPEG side chains. mPEG grafted copolymers (mPEGA-co-AMPS) were characterized by FTIR, H-1 NMR. In this study, dilute solution viscometry measurements were performed to compare the molecular weight effect on fluidity of the copolymers and mechanical properties of the mortar samples prepared by the copolymers were investigated to determine the flexural strength and compressive strengths. It was observed that the reaction pH had a noticeable effect on the molecular weight of the PEG-grafted samples thus causing a significant effect on fluidity. mPEGA-co-AMPS synthesized at a pH of 6 has given the highest fluidity result. Copolymers with mPEG side chains with a molecular weight of 1100 gave higher fluidity and viscosity average molecular weight values than the copolymers with mPEG 2000 side chains. Furthermore, for all the samples tested in this research, increase in molecular weight caused an increase in fluidity, however, a decrease in mechanical properties due to the different air contents of these copolymers. (C) 2009 Elsevier Ltd. All rights reserved.