Treated metal oxide particles and toner compositions

1. A toner composition comprising toner particles and metal oxide particles treated with at least a charge modifying agent, wherein the charge modifying agent is represented by the following formula:

An-Z c —Y b —Ar(EW) a

wherein Ar represents an aromatic group, EW represents an electron withdrawing group, Y represents a spacer group, Z represents an alkylene group, An represents an anchor group, a is an integer from 1 to 5, b is 0 or 1, and c is 0 or 1,

wherein Y is —N(R)—, —N(R)C(O)—, —C(O)N(R)—, —OC(O)—, —C(O)O—, —O—, —S—, —CH═N—, —N═CH—, —N═N—, or —S(O) 2 —, wherein R represents hydrogen or a substituted or unsubstituted aryl or alkyl group,

An is represented by X d SiR′ (3-d) , wherein X represents equal or different hydroloyzable groups or a siloxane group, R′ represents hydrogen or a substituted or unsubstituted aryl or alkyl group, and d is an integer from 1 to 3, and

the metal oxide particles are silica, alumina, ceria, titania, or a mixture thereof.

2. The toner composition of claim 1 , wherein the metal oxide particles are fumed metal oxide particles, co-fumed metal oxide particles, precipitated metal oxide particles, or colloidal metal oxide particles.

3. The toner composition of claim 1 , wherein EW is —NO 2 , —CN, —COCH 3 , —SO 3 H, —SO 2 CH 3 , —F, or —(CF 2 ) n CF 3 , wherein n is 0 or an integer from 1 to 10.

4. The toner composition of claim 1 , wherein the electron withdrawing group is a group having a Hammett Constant of at least 0.2 in either the meta or para position.

5. The toner composition of claim 1 , wherein Z is (CH 2 ) e , wherein e is an integer from 1 to 18.

6. The toner composition of claim 1 , wherein the charge modifying agent is selected from the group consisting of 3-(2,4-dinitrophenylamino) propyltriethoxsilane (DNPS), 3,5-dinitrobenzamido-n-propyltriethoxysilane, 3-(triethoxysilylpropyl)-p-nitrobenzamide (TESPNBA), pentafluorophenyltriethoxysilane (PFPTES), and [2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane (CSPES).

7. The toner composition of claim 1 , wherein the metal oxide particles are also treated with a hydrophobicity-imparting agent.

8. The toner composition of claim 7 , wherein the hydrophobicity-imparting agent is a silazane compound, a siloxane compound, or a silane compound.

9. The toner composition of claim 7 , wherein the hydrophobicity-imparting agent is hexamethyldisilazane (HMDZ), isobutylrimethoxysilane, or octyltrimethoxysilane.

10. The toner composition of claim 7 , wherein the metal oxide particles are colloidal silica, the hydrophobicity-imparting agent is HMDZ, and the charge modifying agent is DNPS.

11. The toner composition of claim 1 , wherein the metal oxide particles are treated with a second charge modifying agent represented by the following formula:

An-Z c —Y b —Ar(EW) a

wherein Ar represents an aromatic group, EW represents an electron withdrawing group, Y represents a spacer group, Z represents an alkylene group, An represents an anchor group, a is an integer from 1 to 5, b is 0 or 1, and c is 0 or 1.

12. The toner composition of claim 11 , wherein the second charge modifying agent is selected such that EW is —F or —(CF 2 ) n CF 3 , wherein n is 0 or an integer from 1 to 10.

13. The toner composition of claim 1 , wherein a loading level of the charge modifying agent on the treated metal oxide particles is in the range from 0.1 to 100 μmol/m 2 .

14. The toner composition of claim 1 , wherein a loading level of the charge modifying agent on the treated metal oxide particles is in the range from 1 to 5 μmol/m 2 .