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Key concepts

Physics and Chemistry of Hybrid Organic-Inorganic Materials Lecture 13: Using surfactants to template materials. Key concepts. Surfactants are amphiphiles with polar head groups and non-polar tails (like soap molecules) Surfactants can be cationic, anionic, or neutral.

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Key concepts

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  1. Physics and Chemistry of Hybrid Organic-Inorganic MaterialsLecture 13: Using surfactants to template materials

  2. Key concepts • Surfactants are amphiphiles with polar head groups and non-polar tails (like soap molecules) • Surfactants can be cationic, anionic, or neutral. • Surfactants can be small molecules or block- copolymers. • Surfactants in water or organic solvents will organize into liquid crystalline like structures with two phases (or more). • Hybrid monomers can be polymerized in one or the other of these phases. • The structure of the surfactant templates the growth of the hybrid material. • Once the polymerization is done, the surfactant can be calcined or extracted out, leaving pores where the surfactant phase resided. • The resulting materials are highly ordered on nm to 10 nm length scales with hierarchical structures. (MCM 41, MCM 48 • Structures include gyroid, double gyorid, hcp, cubic and more.

  3. Chem. Rev., 2002, 102 (11), pp 4093–4138 . Zeolite: silicalite

  4. Templating of structures and pores in hybrids, inorganics and organics In templating, you build a material around some molecule, macromolecules or liquid crystal Opals were used as templates for inverse opals and photonic solids (described in an earlier lecture). At high concentrations, surfactants organize into multi-phase structures that can template structures. This is the mechanism Nature uses to make hybrids like Nacre and bone.

  5. Solvent molecules can act as templates Depending on compliance of network, porosity may be retained or completely lost

  6. Solvent molecules can act as templates

  7. Imprinting is also a kind of pore templating C. Lin, A. Joseph, C.K. Chang, Y.C. Wang, Y.D. Lee Anal. Chim. Acta, 481 (2003), p. 175

  8. Surfactant phase diagrams: oil + water + soap lamellae: stacked 2D layers dispersed spheres of A in body centered cubic array in continuous phase of B. cylinders micelles

  9. A few nanometers in diameter First model for surfactant templating: assumes liquid crystal occupies entire solution

  10. Cited over 10,200 times

  11. Synthesis of MCM-41 spheres 1) n-Hexadecyltrimethylammonium bromide (2.5 g, 0.007 mol) was dissolved in deionized water (50 g) 2) To this surfactant solution, 13.2 g of aqueous ammonia (32 wt.%, 0.25 mol) and 60.0 g of absolute ethanol (EtOH, 1.3 mol) were added and the solution was stirred for 15 min (250 rpm). 3) TEOS (4.7 g, 0.022 mol, freshly distilled) was added at one time resulting in a gel. 4) After stirring for 2 h the white precipitate was filtered and washed with 100 ml of deionized water and 100 ml of methanol. 5) After drying overnight at 363 K, the sample was heated to 823 K (rate:1 K min−1) in air and kept at that temperature for 5 h. Microporous and Mesoporous Materials, 1999, 27, 207–216

  12. Synthesis of MCM-41 silica spheres X-ray diffraction pattern of an MCM-41 sample prepared in heterogeneous medium with n-hexadecylpyridinium chloride as template. Microporous and Mesoporous Materials, 1999, 27, 207–216

  13. Size of MCM 41 pores can be controlled by process conditions

  14. A close look at the structure shows that it is made of small amorphous silica particles TEM image of the honeycomb structure of MCM-41 and a schematic representation of the hexagonal shaped one-dimensional pores. > 1 nm in size Just like the silica in living sponges

  15. X-Ray Diffraction (XRD) These materials show peaks at very small angles = larger structures than are typical in crystalline materials

  16. The Mobil patent was duplicating something already in the literature Somebody did not do a careful literature search!!!!!!

  17. Traditional ionic surfactants used in mesoporous materials templation

  18. Traditional non-ionic surfactants used in mesoporous materials templation

  19. Using other phase separations to control how particles aggregate Smaller structures Hydrophilic Phase Surfactants Polymers Block copolymers Hydrolyzed monomers and polymers are often dissolve in this phase Hydrophobic Phase Larger structures Monomers are often dissolve in this phase Polymers are not very soluble in each other and will phase separate like oil and water

  20. Phase separation: surfactants

  21. Phase separation: surfactants

  22. Adv. Mater 1999, Brinker

  23. Monomer starts reacting and interacting with surfactant as the liquid crystal forms Liquid crystal forms then monomer enters and reacts

  24. MCM-41 MCM-48 SBA-1 SBA-16 FDU-12 FDU-2 Pore models of mesostructures with symmetries of (A) p6mm, (B) Ia3̄d, (C) Pm3̄n, (D) Im3̄m, (E) Fd3̄m, and (F) Fm3̄m.

  25. Published in: Avelino Corma; Chem. Rev. 1997, 97, 2373-2420.

  26. What are some of these materials and what do they look like (SBA-Santa Barbara. Electron micrographs of SBA-1 and SBA-6 along [100] Structure of SBA-1 or SBA-6 observed as an electron density and described either in terms of a clathrate structure or as a surface enveloping the micellar templating agents Nature, 2000, 408, 449

  27. Plane-projection of CDF (a), respective TEM image fragment (b) and its simulation (c).

  28. Chem. Mater., 1996, 8, 1141 Electronic density maps and bicontinuous cubic structure of MCM-48

  29. HREM images of CMK-4 along the three zone axes [100], [110] and [111] together with a representation of the carbonaceous surface. J. Phys. Chem. B, 2002, 106, 1256

  30. Making Hybrid Materials: Class 2C(Templating) Shown here with block copolymer

  31. Polymer phase separation templation of macropores

  32. How organic templates can control porosity of materials Chem. Rev., 2011, 111 (2), pp 765–789

  33. Tools for hierarchical materials structures Phil. Trans. R. Soc. A 28 April 2009 vol. 367 no. 1893 1587-1605

  34. Summary • Surfactants are amphiphiles with polar head groups and non-polar tails (like soap molecules) • Surfactants can be cationic, anionic, or neutral. • Surfactants can be small molecules or block- copolymers. • Surfactants in water or organic solvents will organize into liquid crystalline like structures with two phases (or more). • Hybrid monomers can be polymerized in one or the other of these phases. • The structure of the surfactant templates the growth of the hybrid material. • Once the polymerization is done, the surfactant can be calcined or extracted out, leaving pores where the surfactant phase resided. • The resulting materials are highly ordered on nm to 10 nm length scales with hierarchical structures. (MCM 41, MCM 48 • Structures include gyroid, double gyorid, hcp, cubic and more.

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