Methods comprising providing a relative permeability modifier that comprises a hydrophilic polymer backbone with a hydrophobic modification and incorporating at least one cationic compound onto the hydrophilic polymer backbone. The hydrophilic polymer is one or more of: a polyacrylamide; a polyvinylamine; a poly(vinylamine/vinyl alcohol); an alkyl acrylate polymer; cellulose; chitosan; a polyamide; a polyetheramine; a polyhydroxyetheramine; a polylysine; a polysulfone; a gum; or a starch. The hydrophobic modification is achieved either by reacting the hydrophilic polymer with a hydrophobic compound or by a polymerization reaction product of a hydrophilic monomer and a hydrophobically modified hydrophilic monomer. The hydrophobic compound has an alkyl chain length from 4 to 22 carbons and is one or more of: an alkyl acrylate; an alkyl methacrylate; an alkyl acrylamide; an alkyl methacrylamide; or an alkyl dimethylammoniumethyl methacrylate halide.