Toner additives comprising composite particles

A method of making a composite particle, comprising:

• preparing an aqueous dispersion comprising metal oxide particles;
• adding polymerizable species comprising a first hydrophobizing agent and, optionally, co-monomers and cross-linking agents to the aqueous dispersion to form an emulsion, wherein a mass ratio of the polymerizable species to the metal oxide particles in the emulsion is from 1.5 to 8, wherein the first hydrophobizing agent has the formula [R33-x(OR1)x]SiR2Q, where x is 1, 2, or 3, R1 is methyl or ethyl, R2 is an alkyl linker with the general formula CnH2n, where n=1-10, R3 is methyl or ethyl and Q is a substituted or unsubstituted vinyl, acrylate ester, or methacrylate ester group, with the proviso that when Q is substituted or unsubstituted vinyl, n is 2-10;
• incubating the emulsion for one to three hours at a temperature from 25 to 60° C., wherein the first hydrophobizing agent becomes chemically attached to the metal oxide particles;
• following incubating, adding a polymerization initiator to the aqueous dispersion to form metal oxide-polymer composite particles comprising a polymer matrix and a plurality of metal oxide particles and having have a volume average size from 20 nm to 450 nm, wherein at least a portion of the plurality of metal oxide particles project into and out from the polymer matrix and wherein the metal oxide particles are covalently attached to the polymer via the first hydrophobizing agent.