Examples of preferred polymers include polyacrylic acid, polymethacrylic acid, poly(styrene-acrylic acid), poly(styrene-methacrylic acid), poly(styrene-maleic acid), copolymers of acrylic acid methacrylic acid and alkyl acrylates or methacrylates, poly(ethylene-acrylic acid), or salts thereof. [0031] The coupling agent is a material which couples the pigment and the polymer by activating the carbo