For phosphonated copolymers, the effect of distance of the phosphonate group from the polymer backbone on the Ca2+ chelating capability and the adsorption behavior on cement was studied. For this purpose, 2-acrylamido-2-methylpropane phosphonic acid (AMPPA) and vinyl phosphonic acid (VPA), respectively, were reacted in an aqueous free-radical polymerization with N,N-dimethylacrylamide (NNDMA) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS(R)) to give poly(N,N-dimethylacrylamide-co-2-acrylamido-2-methylpropanesulfonate-co-2-acrylamido-2-methylpropanephosphonate) (CaAMPS(R)-co-NND MA-co-CaAMPPA) and poly(N,N-dimethylacrylamide-co-2-acrylamido-2-methylpropanesulfonate-co-vinylphosphonate) (CaAMPS-co-NNDMA-co-CaVPA), respectively. Adsorption behavior and thus performance of the terpolymers strongly depend on their calcium binding capacity. Ca2+ selective conductivity measurements show that the AMPPA modified terpolymer chelates less calcium than the VPA polymer. Therefore, it interacts less with surfaces containing calcium atoms/ions. To investigate the consequences for practical applications adsorbed amounts on cement surface and effectiveness as water retention agent (fluid loss additive, FLA) in oil well cement slurries with and without acetone-formaldehyde-sulfite (AFS) dispersant were determined. CaAMPS-co-NNDMA-co-CaAMPPA and AFS adsorb simultaneously whereas CaAMPS-co-NNDMA-co-CaVPA does not allow dispersant adsorption. The reason is that affinity of phosphonate functions towards Ca2+ ions is reduced with increasing distance from the polymer backbone. Thus, AMPPA is a weaker anchor group than VPA. Zeta potential measurements indicate that the increased length of the side chain holding the phosphonate function decreases the anionic charge density of the polymer. Accordingly, CaAMPS-co-NNDMA-co-CaAMPPA appears to develop weaker bonds with the cement surface. Upon addition of AFS, the AMPPA modified FLA can change its adsorbed conformation from "train" to "loop" or "tail" mode and thus provide space for the dispersant to adsorb as well. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 1758-1768, 2010