Provided is a composition comprising a pre-formed, hydrolytically susceptible non-addition polyanionic polymer comprising polymer strands formed from at least one ethylenically unsaturated monomer and linking the polymer strands by at least one linking moiety comprising a hydrolytically susceptible bond, wherein at least one of which monomers has: i) one or more functional groups that can be titrated with base to form negatively charged functional groups; or ii) one or more precursor groups that are precursors of the functional groups that can be titrated with base; which precursor groups are converted to the functional groups.