A copolymer for modifying rheology is formed of monomer units consisting essentially of at least one first monomer unit comprising a polyhedral oligomeric silsesquioxane having an ethylenically unsaturated radical at least one second monomer unit comprising an unsaturated oligo-poly(dimethyl siloxane)(meth)acrylate and a sufficient amount of at least one unsaturated water-soluble monomer, such that the copolymer is soluble in water. A composition may comprise an electrolyte and the copolymer. The rheology of an environment comprising an electrolyte may be modified by adding the copolymer to the environment.
