Loretta Ann Grezzo Page

AB diblock copolymers as charge directors in liquid toners

AB diblock copolymer additives offer many process and product improvements in liquid electrostatic toners. One area where AB diblocks are superior is as hydrocarbon-soluble charge directors. Unlike conventional charging agents for liquid toners, which are typically natural occurring substances or by-products of the oil industry, these polymers are synthetic, thus can be made reproducibly and pure. Also, their high molecular weights result in very low toxicity vs. nonpolymeric charge directors. In the past, polymeric charge directors for liquid toners have been random copolymers, made from at least two monomers: a polar one to impart charge, and a non-polar one for hydrocarbon solublity. AB diblock copoiymer charge directors have been found to be superior to conventional and random diblock copolymers.1 In random copolymers, the mixing of the polar and nonpolar components dilute the desired charging, resin compatibility, and hydrocarbon solubility of the additives. With AB diblocks, the non-polar and polar segments of the polymer are completely separated, resulting in a sufactant-type structure, which can form inverse micelles with toner particles in hydrocarbon dispersants. Also, since these polymers are grown stepwise, the length and composition of each block can be precisely controlled to optimize for a specific toner. In this work, syntheses of hydrocarbon-soluble AB diblock quaternary ammonium salts and their behavior as negative charge directors in toners are discussed.