Anisotropic self-assembly of nanoparticles in composites
View Patent ↗An anisotropic self assembled structure comprises isotropic grafted nanoparticles in a polymeric matrix, the self-assembled structure comprising (a) a one-dimensional string of the grafted nanoparticles within the matrix, the string having a width of one nanoparticle and a length of 1-10 nanoparticles, (b) a substantially two-dimensional sheet of the grafted nanoparticles within the matrix, the sheet having a length and a breadth of at least one micron respectively, wherein the sheet is about 2-5 nanoparticles in thickness, or (c) a plurality of three dimensionally interconnected structures where the width of each of the structures is 1-10 nanoparticles; wherein each grafted nanoparticle comprises a substantially spherical inorganic core nanoparticle and a polymeric brush structure grafted thereto.
1. An anisotropic self-assembled structure comprising: a plurality of substantially isotropic grafted nanoparticles in a polymeric matrix, the anisotropic self-assembled structure comprising
(a) a one-dimensional string of the grafted nanoparticles within the polymeric matrix, the string having a width of one nanoparticle and a length of 2-10 nanoparticles,
(b) a substantially two-dimensional sheet of the grafted nanoparticles within the polymeric matrix, the sheet having a length and a breadth of at least one micron respectively, wherein the sheet is about 2-5 nanoparticles in thickness, or
(c) a plurality of three dimensionally interconnected structures where the width of each of the three dimensionally interconnected structures is 1-10 nanoparticles;
wherein each grafted nanoparticle comprises a substantially spherical inorganic core nanoparticle and an organic brush structure grafted thereto, the organic brush structure and the polymeric matrix being molecules not covalently attached to one another, the organic brush structure and the polymeric matrix independently comprising a polymer, the polymer having the same chemical structure in the polymeric matrix as in the organic brush structure but with a different length, and wherein
the brush structure comprises a plurality of grafted polymeric chains of a weight average molecular weight M g ,
the polymeric matrix has a weight average molecular weight of M that is greater than about 120 kDa, wherein M g /M is equal to or less than 7, and
there is an average number of grafted polymeric chains per nm 2 of surface of the inorganic core nanoparticles D, wherein 0.01 chains/nm 2 <D<0.1 chains/nm 2 .
2. The anisotropic self-assembled structure of claim 1 wherein M g /M<1 and 0.05 chains/nm 2 <D<0.10 chains/nm 2 , wherein the anisotropic self-assembled structure comprises (b) a substantially two-dimensional sheet of the grafted nanoparticles within the polymeric matrix, the sheet having a length and a breadth of at least one micron respectively, wherein the sheet is about 2-5 nanoparticles in thickness, or (c) a plurality of three dimensionally interconnected structures where the width of each of the three dimensionally interconnected structures is 1-10 nanoparticles.
3. The anisotropic self-assembled structure of claim 1 wherein 1<M g /M<about 3 and 0.01 chains/nm 2 <D<about 0.10 chains/nm 2 , wherein the self-assembled structure comprises
(a) a one-dimensional string of the grafted nanoparticles within the polymeric matrix, the string having a width of one nanoparticle and a length of 2-10 nanoparticles,
(b) a substantially two-dimensional sheet of the grafted nanoparticles within the polymeric matrix, the sheet having a length and a breadth of at least one micron respectively, wherein the sheet is about 2-5 nanoparticles in thickness, or
(c) a plurality of three dimensionally interconnected structures where the width of each of the three dimensionally interconnected structures is 1-10 nanoparticles.
4. The anisotropic self-assembled structure of claim 1 wherein about 3<M g /M<about 7 and 0.01 chains/nm 2 <D<about 0.05 chains/nm 2 , wherein the self assembled structure comprises
(a) a one-dimensional string of the grafted nanoparticles within the polymeric matrix, the string having a width of one nanoparticle and a length of 2-10 nanoparticles,
(b) a substantially two-dimensional sheet of the grafted nanoparticles within the polymeric matrix, the sheet having a length and a breadth of at least one micron respectively, wherein the sheet is about 2-5 nanoparticles in thickness, or
(c) a plurality of three dimensionally interconnected structures where the width of each of the three dimensionally interconnected structures is 1-10 nanoparticles.
5. The anisotropic self-assembled structure of claim 1 wherein substantially all of the plurality of grafted nanoparticles have a respective inorganic core comprising silica.
6. The anisotropic self-assembled structure of claim 1 wherein substantially all of the plurality of grafted nanoparticles comprises nanoparticles wherein the inorganic core has an average particle diameter of about 14±4 nm.
7. The anisotropic self-assembled structure of claim 1 wherein the brush structure comprises polystyrene and M g is about 100-120 kDa, or the brush structure comprises poly(methylmethacrylate) and M g is about 85 kDa.
8. The anisotropic self-assembled structure of claim 1 wherein the brush structure comprises polystyrene chains.
9. The anisotropic self-assembled structure of claim 1 wherein there are about 25-45 grafted polymeric organic chains per nanoparticle.
10. The anisotropic self-assembled structure of claim 1 wherein the polymeric matrix comprises polystyrene or polymethylmethacrylate.
11. The anisotropic self-assembled structure of claim 1 wherein the polymeric matrix comprises polystyrene having a weight average molecular weight of greater than about 120 kDa.
12. The anisotropic self-assembled structure of claim 1 wherein the polymeric matrix comprises poly(methylmethacrylate) having a weight average molecular weight of greater than about 180 kDa.
13. The anisotropic self-assembled structure of claim 1 comprising a one-dimensional string of the grafted nanoparticles within the polymeric matrix, the string having a width of one nanoparticle and a length of 2-10 nanoparticles.
14. The anisotropic self-assembled structure of claim 1 comprising a substantially two-dimensional sheet of the grafted nanoparticles within the polymeric matrix, the sheet having a length and a breadth of at least one micron respectively, wherein the sheet is about 2-5 nanoparticles in thickness.
15. The anisotropic self-assembled structure of claim 1 comprising a plurality of three dimensionally interconnected structures where the width of each of the three dimensionally interconnected structures is 1-10 nanoparticles.
16. The anisotropic self-assembled structure of claim 1 wherein the anisotropic self-assembled structure in the polymeric matrix comprises about 1-10% of a weight of the inorganic core.
17. The anisotropic self-assembled structure of claim 11 comprising a plurality of layers of the substantially two-dimensional sheets in a stack.
18. A method of preparing the anisotropic self-assembled structure of claim 1 , the method comprising forming a dispersion of a plurality of the grafted nanoparticles in the polymeric matrix, then, annealing the residue at a temperature above a glass transition temperature of the polymeric matrix for a duration of time sufficient to bring about formation of the anisotropic self-assembled structure within the polymeric matrix.
19. The method of claim 18 wherein substantially all of the plurality of grafted nanoparticles have a respective inorganic core comprising silica.
20. The method of claim 18 wherein substantially all of the plurality of grafted nanoparticles comprise an inorganic core with an average particle diameter of about 14±4 nm.
21. The method of claim 18 the brush structure comprises polystyrene and M g is about 100-120 kDa, or the brush structure comprises poly(methylmethacrylate) and M g is about 85 kDa.
22. The method of claim 18 wherein the brush structure comprises polystyrene chains.
23. The method of claim 18 wherein there are about 25-45 grafted polymeric organic chains per nanoparticle.
24. The method of claim 18 wherein the polymeric matrix comprises polystyrene or polymethylmethacrylate.
25. The method of claim 18 wherein the polymeric matrix has a weight average molecular weight of greater than about 150 kDa.
26. The method of claim 18 wherein the polymeric matrix comprises poly(methylmethacrylate) having a weight average molecular weight of greater than about 180 kDa.
27. The method of claim 18 wherein the anisotropic self-assembled structure comprises a one-dimensional string of the drafted nanoparticles within the polymeric matrix, the string having a width of one nanoparticle and a length of 2-10 nanoparticles.
28. The method of claim 18 wherein the anisotropic self-assembled structure comprises a substantially two-dimensional sheet of the grafted nanoparticles within the polymeric matrix, the sheet having a length and a breadth of at least one micron respectively, wherein the sheet is about 2-5 nanoparticles in thickness.
29. The method of claim 18 wherein the anisotropic self-assembled structure comprises a plurality of three dimensionally interconnected structures where the width of each of the structures is 1-10 nanoparticles.
30. The method of claim 18 wherein the anisotropic self-assembled structure in the polymeric matrix comprises about 1-10 wt % of the inorganic core.
31. The method of claim 18 comprising forming the dispersion in a solvent, then casting the dispersion on a surface, then removing the solvent.
32. The method of claim 18 wherein the annealing temperature is greater than about 150° C.
33. The method of claim 18 wherein the annealing temperature is greater than about 200° C.
34. The method of claim 18 wherein the annealing time is about 1 to about 20 days.
35. A synthetic substitute for bone or tooth enamel comprising the anisotropic self-assembled structure of claim 1 .
36. A fuel cell comprising the anisotropic self-assembled structure of claim 1 .
37. A flame-retardant material comprising the anisotropic self-assembled structure of claim 1 .
38. An electroconductive material comprising the anisotropic self-assembled structure of claim 1 .
39. The anisotropic self-assembled structure of claim 1 , wherein
(a) the polymeric matrix and the organic brush structure each comprise polystyrene, or
(b) the polymeric matrix and the brush structure each comprise polymethylmethacrylate
(c) both (a) and (b).