Polymer-encapsulated nanoparticle systems

Abstract

A polymer-encapsulated nanoparticle system includes a non-aqueous medium; and polymer-encapsulated nanoparticles formed in situ in the non-aqueous medium. Each polymer-encapsulated particle has a diameter that is less than 1 micron, and includes a solid particle core, and a polymer coating established directly on the solid particle core.

1 . A polymer-encapsulated nanoparticle system, comprising:
 a non-aqueous medium; and   polymer-encapsulated nanoparticles formed in situ in the non-aqueous medium, each polymer-encapsulated particle having a diameter that is less than 1 micron and including:
 a solid particle core; and 
 a polymer coating established directly on the solid particle core. 
   
     
     
         2 . The polymer-encapsulated nanoparticle system as defined in  claim 1  wherein the non-aqueous medium is a dielectric material, and wherein the polymer coating of the polymer-encapsulated nanoparticles further includes an ionic species configured to promote charging of the polymer coating. 
     
     
         3 . The polymer-encapsulated nanoparticle system as defined in  claim 2  wherein the ionic species is an aliphatic acid salt of a chain aliphatic derivative containing one of acids and bases, wherein the chain aliphatic derivative includes at least 5 carbon atoms, and wherein the acids are selected from oleic, valeric, hexanoic, heptanoic, caprylic, nonanoic, capric, lauric, myristic, palmitic, heptadecanoic, stearic, arachidic, behenic, lignoceri, sulfuric, phosphoric, boronic, sulfonic, sulfamic, nitric, nitrous, nitrosulfuric, and pyrophosphoric acids, or wherein the bases are selected from primary, secondary, tertiary, quaternary, and aromatic amines. 
     
     
         4 . The polymer-encapsulated nanoparticle system as defined in  claim 1  wherein the non-aqueous medium is a non-oxidative water immiscible medium. 
     
     
         5 . A field responsive system, comprising:
 a non-aqueous dielectric medium;   polymer-encapsulated nanoparticles formed in situ in and dispersed in the non-aqueous dielectric medium, each polymer-encapsulated particle having a diameter that is less than 1 micron and including:
 a solid particle core; and 
 a polymer coating established directly on the solid particle core, the polymer coating including an ionic species which imparts a reversible charge to each polymer-encapsulated nanoparticle; and 
   a source of an electric field configured to charge the polymer-encapsulated nanoparticles in a predetermined manner.   
     
     
         6 . A method for forming a system including polymer-encapsulated nanoparticles, the method comprising:
 forming an inverse mini-emulsion including a continuous phase of a non-aqueous medium and a discontinuous phase of at least: a plurality of nanoparticles having a polar surface, and at least one of i) a polar, water-soluble, or water-miscible monomer, or ii) a polar, water-soluble, or water-miscible pre-polymer; and   initiating polymerization of the at least one of the monomer or the prepolymer to form a polymer coating on each of the plurality of nanoparticles in the non-aqueous medium.   
     
     
         7 . The method as defined in  claim 6  wherein the forming of the inverse mini-emulsion is accomplished in the absence of water. 
     
     
         8 . The method as defined in  claim 6  wherein the at least one of i) the polar, water-soluble, or water-miscible monomer, or ii) the polar, water-soluble, or water-miscible pre-polymer is a solid, and wherein prior to forming the inverse mini-emulsion, the method further comprises:
 dissolving the at least one of i) the polar, water-soluble, or water-miscible monomer, or ii) the polar, water-soluble, or water-miscible pre-polymer; and 
 adding the plurality of nanoparticles to the aqueous solvent. 
 
     
     
         9 . The method as defined in  claim 6  wherein forming the inverse mini-emulsion includes:
 mechanically mixing the plurality of nanoparticles, a radical initiator, and the at least one i) the polar, water-soluble, or water-miscible monomer, or ii) the polar, water-soluble, or water-miscible pre-polymer, thereby forming a mixture; 
 adding a surfactant or dispersant dissolved in the non-aqueous medium to the mixture; 
 subjecting the mixture to mixing at a rate greater than or equal to 0.5 k rpm to form a suspension; and 
 microhomogenizing the suspension at a predetermined pressure for a predetermined number of cycles. 
 
     
     
         10 . The method as defined in  claim 9  wherein microhomogenizing includes exposing the suspension to a pressurized chamber, wherein the predetermined pressure is up to 33,000 psi, and wherein the predetermined number of cycles ranges from 1 to 6, where each cycle is 5 minutes at 250 mL/min. 
     
     
         11 . The method as defined in  claim 9 , further comprising adding a charge generating component during the mechanically mixing step. 
     
     
         12 . The method as defined in  claim 11  wherein the charge generating component is an aliphatic acid salt of a chain aliphatic derivative containing one of acids and bases, wherein the chain aliphatic derivative includes at least 5 carbon atoms, and wherein the acids are selected from oleic, valeric, hexanoic, heptanoic, caprylic, nonanoic, capric, lauric, myristic, palmitic, heptadecanoic, stearic, arachidic, behenic, lignoceri, sulfuric, phosphoric, boronic, sulfonic, sulfamic, nitric, nitrous, nitrosulfuric, and pyrophosphoric acids, or wherein the bases are selected from primary, secondary, tertiary, quaternary, and aromatic amines. 
     
     
         13 . The method as defined in  claim 9  wherein an amount of the surfactant ranges from about 0.01 wt % to about 40 wt % of a total weight of the surfactant or dispersant dissolved in the non-aqueous medium. 
     
     
         14 . The method as defined in  claim 6 , further comprising selecting the plurality of nanoparticles from the group consisting of carbon black, copper phthalocyanine, titania, and silica. 
     
     
         15 . The method as defined in  claim 6  wherein initiating polymerization of the inverse mini-emulsion is accomplished at a predetermined temperature. 
     
     
         16 . The method as defined in  claim 15 , further comprising including a crosslinker and an initiator in the discontinuous phase. 
     
     
         17 . The method as defined in  claim 6 , further comprising including a charge generating component in the discontinuous phase. 
     
     
         18 . The method as defined in  claim 6 , further comprising including at least one of a surfactant, a dispersant, a crosslinker, an initiator, a rheology modifier, and an acid-group containing monomer in the discontinuous phase. 
     
     
         19 . The method as defined in  claim 6 , further comprising adding a polar, water-soluble, or water-miscible polymer to the discontinuous phase. 
     
     
         20 . The method as defined in  claim 6  wherein each polymer-encapsulated particle has a diameter that is less than 1 micron.