Method of producing hybrid polymer-inorganic materials

• US 20060257485A1
• Filed: 03/10/2004
• Published: 11/16/2006
• Est. Priority Date: 03/13/2003
• Status: Active Grant

• Current Assignee: Eugenia Kumacheva
• Original Assignee: Eugenia Kumacheva
• Inventors: Kumacheva, Eugenia
• Granted Patent: US 7,820,737 B2
• Time in Patent Office: Days
• US Class Current: 424/486
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C08G 83/001 Macromolecular compounds containing organic and inorganic sequences, e.g. organic polymers grafted onto silica
• CPC Class Codes: C08J 5/005 Reinforced macromolecular compounds with nanosized materials, e.g. nanoparticles, nanofibres, nanotubes, nanowires, nanorods or nanolayered materials

Abstract

The present invention describes a new approach to producing hybrid composite materials with multiscale morphologies. We doped polymer submicrometer spheres with semiconductor or metal (e.g. CdS or Ag, respectively) nanoparticles and used these doped microspheres as the functional building blocks in production of hybrid periodically structured materials. The preparation of hybrid polymer particles included the following stages: (i) synthesis of monodisperse polymer microspheres, (ii) in-situ synthesis of the inorganic nanoparticles either on the surface, or in the bulk of the polymer beads, and (iii) encapsulation of hybrid microspheres with a hydrophobic shell. We demonstrated that by changing the composition of the polymer beads good control could be achieved over the size of the nanoparticles.

Claims

1. A process of synthesizing a composite colloidal polymer-inorganic material, comprising the steps of:

a) synthesizing a dispersion of polymer microparticles in a liquid;

b) treating said dispersion of polymer microparticles to modify an outer surface of the polymer microparticles to provide an effective concentration of ligands on the outer surface of the polymer microparticles, the ligands being selected to form a complex with atoms of a metal, ions of the metal, or molecular moieties containing the metal at the surface of the polymer microparticle;

c) adding atoms of the metal, ions of the metal, or molecular moieties containing the metal to the dispersion of polymer microparticles under conditions suitable to facilitate formation of a complex between the ligands and the atoms of the metal, ions of the metal, or molecular moieties at the surface of the polymer microparticles; and

d) exposing the dispersion of polymer microparticles to an effective agent which interacts with the atoms of the metal, ions of the metal, or molecular moieties containing the metal to form nanoparticles on the outer surface of the polymer microparticles, the nanoparticles being comprised of at least the metal, the effective concentration of ligands being selected to give nanoparticles with specified material properties.

2. The process according to claim 1 including encapsulating the polymer microparticles with the nanoparticles on the outer surface thereof in a polymeric shell, and annealing the encapsulated polymer microparticles with the nanoparticles on the outer surface thereof together to form a periodic array of polymer microparticles.

3. The process according to claim 1 wherein the specified material properties include size, morphology and crystallinity of the nanoparticles which permit control over optical, electronic and magnetic properties of the nanoparticles.

4. The process according to claim 1, wherein the step of treating said dispersion of polymer microparticles to modify an outer surface of the polymer microparticles provides electrically charged ligands which facilitate formation of an electrical double layer into which ions of opposite electrical charge are incorporated.

5. The process according to claim 4 wherein the electrically charged ligands are negatively charged, and wherein the ions of opposite electrical charge are cations of the metal.

6. The process according to claim 4 wherein the electrically charged ligands are positively charged, including adding a selected anion to the dispersion wherein the anions coordinate with the positively charged ligands to form a negatively charged ligand-anion complex, and wherein cations of the metal are incorporated into an electrical double layer produced by the negatively charged ligand-anion complex.

7. The process according to claim 6 wherein the cations of the metal are added to the dispersion in a salt of the metal, and wherein the effective agent is a reducing agent, and wherein the nanoparticles comprise the selected metal by itself.

8. The process according to claim 5 wherein the cations of the metal are added to the dispersion in a salt of the metal, and wherein the effective agent is a reducing agent, and wherein the nanoparticles comprise the selected metal by itself.

9. The process according to claim 5 wherein the effective agent includes anions which react with the metal cations to form a compound, the nanoparticles being comprised of the compound.

10. The process according to claim 9 wherein the compound is one of a semiconductor, metal hydroxide and metal oxide.

11. The process according to claim 9 wherein the metal ion is Cd⁺², and the anion is S⁻

2, and wherein the compound is a semiconductor CdS.

12. The process according to claim 10 wherein the semiconductor is selected from the group consisting of CdS, PbS, CdSe and CdTe.

13. The process according to claim 8 wherein the metal is silver and the metal salt is a silver salt, and wherein the nanoparticles are silver nanoparticles.

14. The process according to claim 13 wherein the silver salt is AgNO₃ contained in an aqueous solution, and wherein the reducing agent is NaBH₄ contained in a solution mixed with the dispersion of core polymer microparticles.

15. The process according to claim 7 wherein the metal is selected from the group consisting of Ag, Au, Co, Ni, Fe, Ag, Au, Co, Mn, Ni, Fe, Pt, Ta, W, Cu, Si, Mo, Zn, Cd, Nb, Y, Ge, Sn, Pb, Al, Ga, In and Ti.

16. The process according to claim 8 wherein the metal is selected from the group consisting of Ag, Au, Co, Ni, Fe, Ag, Au, Co, Mn, Ni, Fe, Pt, Ta, W, Cu, Si, Mo, Zn, Cd, Nb, Y, Ge, Sn, Pb, Al, Ga, In and Ti.

17. The process according to claim 5 wherein the wherein the cations of the metal are added to the dispersion in a salt of the metal, and wherein the effective agent includes oxide anions which react with the metal cations to form a metal oxide, the nanoparticles being comprised of the metal oxide.

18. The process according to claim 17 wherein the metal is selected from the group consisting of Ag, Au, Co, Ni, Fe, Ag, Au, Co, Mn, Ni, Fe, Pt, Ta, W, Cu, Si, Mo, Zn, Cd, Nb, Y, Ge, Sn, Pb, Al, Ga, In and Ti.

19. The process according to claim 1 wherein the polymer microparticles are selected from the group consisting of poly(methyl methacrylate-methacrylic acid) (PMMA-PMAA) latex, and crosslinked poly(styrene-acrylic acid) (PS-PAA) latexes.

20. The process according to claim 1 wherein the step of synthesizing a dispersion of polymer microparticles includes synthesizing the polymer microparticles containing carboxyl (COOH) groups, and wherein the step of treating the dispersion of polymer microparticles to modify an outer surface of the polymer microparticles includes deprotonation of the COOH groups to produce charged COO⁻

groups on the surface of the polymer microparticles which contribute to formation of the electrical double layer.

21. The process according to claim 20 wherein deprotonation of the COOH groups is achieved by mixing a solution containing KOH with the dispersion of polymer microparticles.

22. The process according to claim 20 wherein the dispersion is synthesized with the polymer microparticles present in an amount of about 20 wt % of polymer particles.

23. The process according to claim 20, wherein the step of encapsulating the polymer microparticles with the nanoparticles on the outer surface thereof in a polymeric shell includes surfactant-free emulsion polymerization of a selected shell-forming polymer on the surface of the polymer microparticles containing the nanoparticles on the surfaces thereof.

24. The process according to claim 23 wherein the selected shell-forming polymer is polystyrene-poly(methyl methacrylate)-polyacrylic acid-poly(butyl methacrylate) copolymer with a weight ratio of about 2.5/10/1/2.5, respectively.

25. The process according to claim 1 wherein the polymer microparticles are microspheres synthesized with a diameter in a range from about 20 nm to about 200 microns.

26. The process according to claim 1 wherein the polymer microparticles are substantially monodisperse microspheres.

27. The process according to claim 1 wherein the polymer microparticles are synthesized with at least two polymer constituents in pre-selected ratios to each other, the pre-selected ratios of the various polymer constituents being selected to give nanoparticles having pre-selected properties.

28. The process according to claim 1 wherein the polymer microparticles are synthesized from a polymer material having at least one functional group which can be selectively ionized during the step of treating said dispersion of polymer microparticles to modify an outer surface of the polymer microparticles provides electrically charged ligands.

29. The process according to claim 28 wherein said at least one functional group is carboxyl (COOH).

30. A process of synthesizing a composite colloidal polymer-inorganic material, comprising the steps of:

a) synthesizing a dispersion of polymer microgel particles in a liquid;

b) treating said dispersion of polymer microgel particles to modify an interior of the polymer microgel particles to provide an effective concentration of ligands in the interior of the polymer microgel particles, the ligands being selected to form a complex with atoms of a metal, ions of the metal, or molecular moieties containing the metal in the interior of the polymer microparticle;

c) adding atoms of the metal, ions of the metal, or molecular moieties containing the metal to the dispersion of polymer microgel particles under conditions suitable to facilitate uptake of the atoms of the metal, ions of the metal, or molecular moieties into the interior of the polymer microgel particles;

d) exposing the dispersion of polymer microgel particles to a first effective agent which interacts with the atoms of the metal, ions of the metal, or molecular moieties in the interior of the polymer microgel particles to form nanoparticles in the interior of the polymer microgel particles, the nanoparticles being comprised of at least the metal, the effective concentration of ligands being selected to give nanoparticles with specified material properties;

e) exposing the polymer microgel particles to a second effective agent which results in the polymer microgel particles expelling the liquid therefrom which causes the polymer microgel particles to contract in volume; and

f) encapsulating the contracted polymer microgel particles with the nanoparticles in the interior thereof in a protective polymeric shell material, the protective polymeric shell material being effective to suppress interactions between the contracted polymer microgel particles and the liquid.

31. The process according to claim 30 including encapsulating the polymer microgel particles with the nanoparticles contained therein in an outer polymeric shell, and annealing the encapsulated polymer microgel particles to form a periodic array of polymer microgel particles.

32. The process according to claim 30 wherein the specified material properties include size, morphology and crystallinity of the nanoparticles.

33. The process according to claim 30, wherein the step of treating said dispersion of polymer microgel particles to modify an interior of the polymer microgel particles provides electrically charged ligands which facilitate formation of an electrical double layer into which ions of opposite electrical charge are incorporated.

34. The process according to claim 33 wherein the electrically charged ligands are negatively charged, and wherein the ions of opposite electrical charge are cations of the metal.

35. The process according to claim 33 wherein the electrically charged ligands are positively charged, including adding a selected anion to the dispersion wherein the anions coordinate with the positively charged ligands to form a negatively charged ligand-anion complex, and wherein cations of the metal are incorporated into an electrical double layer produced by the negatively charged ligand-anion complex.

36. The process according to claim 34 wherein the cations of the metal are added to the dispersion in a salt of the metal, and wherein the first effective agent is a reducing agent, and wherein the nanoparticles comprise the selected metal by itself.

37. The process according to claim 34, wherein the first effective agent includes anions which react with the metal cations to form a compound, the nanoparticles being comprised of the compound.

38. The process according to claim 37 wherein the compound is one of a semiconductor, metal hydroxide and metal oxide.

39. The process according to claim 37 wherein the metal ion is Cd⁺², and the anion is S⁻

2, and wherein the compound is a semiconductor CdS.

40. The process according to claim 39 wherein the semiconductor is selected from the group consisting of CdS, PbS, CdSe and CdTe.

41. The process according to claim 36 wherein the metal is silver and the metal salt is a silver salt, and wherein the nanoparticles are silver nanoparticles.

42. The process according to claim 41 wherein the Ag nanoparticles exhibit fluorescence upon illumination with UV light.

43. The process according to claim 41 wherein the silver salt is AgNO₃ contained in an aqueous solution, and wherein the reducing agent is NaBH₄ contained in a solution mixed with the dispersion of core polymer microparticles.

44. The process according to claim 30, wherein the metal is selected from the group consisting of Ag, Au, Co, Ni, Fe, Ag, Au, Co, Mn, Ni, Fe, Pt, Ta, W, Cu, Si, Mo, Zn, Cd, Nb, Y, Ge, Sn, Pb, Al, Ga, In and Ti.

45. The process according to claim 38 wherein the wherein the cations of the metal are added to the dispersion in a salt of the metal, and wherein the effective agent includes oxide anions which react with the metal cations to form a metal oxide, the nanoparticles being comprised of the metal oxide.

46. The process according to claim 45 wherein the metal is selected from the group consisting of Ag, Au, Co, Ni, Fe, Ag, Au, Co, Mn, Ni, Fe, Pt, Ta, W, Cu, Si, Mo, Zn, Cd, Nb, Y, Ge, Sn, Pb, Al, Ga, In and Ti.

47. The process according to claim 30 wherein the step of synthesizing a dispersion of polymer microgel particles includes copolymerization of N-isopropyl acrylamide (NIPAM), acrylic acid (AA), and 2-hydroxyethyl acrylate (HEA) using precipitation polymerization, and wherein the polymer microgel particles contain carboxyl (COOH) groups, and wherein the step of treating the dispersion of polymer microgel particles in such as way as to ionize the functional groups in the interior of the polymer microgel particles includes deprotonation of the COOH groups to produce charged COO³¹ groups in the interior of the polymer microgel particles.

48. The process according to claim 47 wherein the step of encapsulating the polymer hydrogel microparticles with the nanoparticles in the interior thereof in a polymeric shell includes encapsulating the PNIPAM-PAA-PEHA microgel particles with a hydrophobic poly(methyl methacrylate)-poly(butyl acrylate)-polyacrylic acid shell (weight ratio 15/4/1, respectively).

49. The process according to claim 30 wherein the dispersion is synthesized with the polymer microgel particles present in an amount of about 1 to about 10 wt % of polymer microgel particles.

50. The process according to claim 30 wherein the dispersion is synthesized with the polymer microgel particles present in an amount of about 1 to about 2 wt % of polymer microgel particles.

51. The process according to claim 30 wherein the step of synthesizing a dispersion of polymer microgel particles includes synthesizing crosslinked poly(styrene-acrylic acid) (PS-PAA) latex microparticles and transforming said crosslinked poly(styrene-acrylic acid) (PS-PAA) latex microparticles into microgel particles by exposure to an aqueous solution at sufficiently high pH.

52. The process according to claim 30 wherein the second effective agent includes change in temperature, change in pH or change in ionic strength of the liquid medium.

56. The process according to claim 44 wherein the electrically charged ligands are positively charged, including adding a selected anion to the dispersion wherein the anions coordinate with the positively charged ligands to form a negatively charged ligand-anion complex, and wherein cations of the metal are incorporated into an electrical double layer produced by the negatively charged ligand-anion complex.

57. The process according to claim 56 wherein the cations of the metal are added to the dispersion in a salt of the metal, and wherein the effective agent is a reducing agent, and wherein the nanoparticles comprise the selected metal by itself.

53. A process of synthesizing a composite colloidal polymer-inorganic material, comprising the steps of:

a) synthesizing a dispersion including polymer microparticles in a liquid;

b) encapsulating the polymer microparticles in a shell forming polymer microgel prepared by,

treating the polymer microparticles to provide an effective concentration of ligands, the ligands being selected to form a complex with atoms of a metal, ions of the metal, or molecular moieties containing the metal at the surface of the polymer microparticles,

adding atoms of the metal, ions of the metal, or molecular moieties containing the metal to the shell forming polymer microgel under conditions suitable to facilitate formation of a complex between the ligands and the atoms of the metal, ions of the metal, or molecular moieties at the surface of the polymer microparticles, and

exposing the polymer microgel to an effective agent which interacts with the atoms of a metal, ions of the metal, or molecular moieties containing the metal to form nanoparticles dispersed throughout the polymer microgel, the nanoparticles being comprised of at least the metal, the effective concentration of ligands being selected to give nanoparticles with specified material properties;

c) exposing the polymer microgel to a second effective agent which results in the polymer microgel particles expelling the liquid therefrom which causes the polymer microgel to contract in volume around the polymer microparticles; and

d) annealing the polymer microparticles encapsulated in the shell forming polymer microgel having the nanoparticles embedded therein to form a periodic array of polymer microgel particles.

54. The process according to claim 53 wherein the step of treating said dispersion of polymer microparticles to modify an outer surface of the polymer microparticles provides electrically charged ligands which facilitate formation of an electrical double layer into which ions of opposite electrical charge are incorporated.

55. The process according to claim 54 wherein the electrically charged ligands are negatively charged, and wherein the ions of opposite electrical charge are cations of the metal.

58. The process according to claim 55 wherein the cations of the metal are added to the dispersion in a salt of the metal, and wherein the effective agent is a reducing agent, and wherein the nanoparticles comprise the selected metal by itself.

59. The process according to claim 55 wherein the first effective agent includes anions which react with the metal cations to form a compound, the nanoparticles being comprised of the compound.

60. The process according to claim 59 wherein the compound is one of a semiconductor, metal hydroxide and metal oxide.

61. The process according to claim 53, wherein the specified material properties include size, morphology and crystallinity of the nanoparticles.

62. The process according to claim 53, wherein the second effective agent includes change in temperature, change in pH or change in ionic strength of the liquid medium.