Polymer-encapsulated colorant nanoparticles

A negatively charged polymer-encapsulated colorant nanoparticle, comprising:

• a colorant nanoparticle core;
• a polymer coating covalently bonded or physically bonded to the surface of the colorant nanoparticle core, the polymer coating having been formed from preformed polymers selected from copolymers of ethylene and methacrylic acid, copolymers of ethylene and acrylic acid, terpolymers of ethylene, methacrylic acid, and acrylate, polyethylene homopolymers, oxidized polyethylene homopolymers, high-density oxidized polyethylene homopolymers, polypropylene homopolymers, copolymers of ethylene and vinyl acetate, copolymers of oxidized ethylene and vinyl acetate, ethylene maleic anhydride copolymers, propylene maleic anhydride copolymers, and combinations thereof;
• a negatively charged functional group present on the surface of the polymer-encapsulated colorant nanoparticle, wherein each negatively chargeable functional group present on the surface of the polymer-encapsulated colorant nanoparticle is negatively charged, the polymer-encapsulated colorant nanoparticle having been formed in situ in a non-aqueous carrier by microfluidization;
• and
• a charge director to impart the negative charge to the negatively chargeable functional group.