Chemistry and Physics of Hybrid Materials

1. Chemistry and Physics of Hybrid Materials Lecture 2

2. Today • Quiz #1 • Biohybrids • Tools for making hybrids

3. Hybrid Organic-Inorganic materials are common in nature: composites Animals Organic phase is biopolymers Nacre Plants phytolith Argonite (CaCO3) plates as inorganic with protein (polyamide) as organic Teeth, spines in echinderms Mussel shells, sponges, diatoms and corals are utilize hybrid organic-inorganic materials Carbohydrates are the template and organic phase

4. Silica - SiO2 radiolaria diatoms

5. Colloidal silica in diatoms: Hierarchical structure pH ≈ 5 Silica walls are build up from ca. 5nm particles to give ca. 40nm diameter particles that are organized within the frustule.

6. What is a hierarchical structure? In materials, a structure with different structures at different length scales: like in tendons (above)

7. More Bio-Hybrids based on CaCO3: Nacre Argonite (CaCO3) plates as inorganic phase with protein (polyamide) as organic phase Fracture strength is 3000 times higher than its mineral constituent CaCO3. Mother-of-pearl Opalescence from light diffraction in nacre (argonite blocks height ≈ λ light)

8. The hierarchical structure of nacre Macromolecular Growth rings (mesolayers) Phase morphology The shell itself Inner surface of shell (mother or pearl) Long range order: stacked crystals argonite crystal structure Barthelat F Phil. Trans. R. Soc. A 2007;365:2907-2919

9. Lobster exoskelton CaCO3 & Carbohydrate & protein

10. Teeth: Enamel, dentin, and cementum Apatite – hydrated CaPO4 Protein– collagen & others

11. Bones Apatite – hydrated CaPO4 Protein– collagen 200 MPa yield strength 30 MPaM0.5 toughness

12. Echinoderm spine CaCO3 Protein templating

13. Phytoliths SiO2 silica 2-3% silicon by weight Horsetail, banana leaves

14. Silica in Sponges

15. Bio Hybrid Organic-Inorganic Materials Sophisticated, highly evolved hybrids -nominally weak, but bio-accessible minerals (eg. CaCO3) -hydrophilic, water plasticized biopolymers (eg. protein) -Integrated at nano-length scales -Phase separation templating of hierarchical structures -All water based chemistry!! The ultimate green chemistry Optimized to give non-additive property (synergistic effects) Models for many research programs in hybrid materials

16. Making hybrids ourselves

17. Class 1 Hybrids: No covalent bonds between organic & inorganic phases

18. Class 2 Hybrids: Covalent bonds between organic & inorganic phases Life uses Class 2C approach to make biohybrids

19. Tools for making hybrids • Chemical reactions • Do both inorganic and organic undergo reactions • Which reactions are first • What are the relative rates • Physics: Changes in state or properties • Do either or both organic and inorganic change phase due to chemistry or temperature/solvent • What is the timing of phase change relative to chemical reactions • Together these determine if hybrid is multiphase and the size, structure, and morphology of phase(s)

20. For example: chemical hybrids (Class 2A) • Fast chemical reactions at both inorganic and organic (part of one monomer) • Change in phase very slow compared to chemistry Formation of hybrid networks, and thermodynamic gelation

21. For example: Physical hybridsClass 1A • Organic and inorganic phases are preassembled, then physically mixed above the melting point of the organic, then cooled • Long range structure and morphology are affected Formation of hybrid networks, and gelation

22. Some hybrid monomers: • Polymerize by hydrolysis and condensation (sol-gel polymerization) • Monomers 2-4 polymerize to class 2 materials • But act like class 1 in many cases. • Used for many of the other classes as the inorganic component.

23. Inorganic Phases Preformed inorganic clusters Silica Particles POSS

24. Inorganic Phases Carbon Buckeyballs, nanotubes and graphene Nature Materials 9, 868–871 (2010)

25. Making Hybrid Materials: Class 1A (pre-formed particles and fibers) Physical mixing or particles

26. Making Hybrid Materials: Class 1B (in situ particle growth) No Solvent except for monomer(s) Generally uses low tg organic polymers or in polymer melts (< 100 °C).

27. Making Hybrid Materials: Class 1C(Polymerizing in pores) Non-porous composite material • Porous metal oxide • Liquid monomer (no solvent) • UV, heat, radiation

28. Making Hybrid Materials: Class 1D(encapsulation of small organics) • Polymerize metal oxide around organic • pores must be small or leakage will occur • Solid state dye lasers, filters, colored glass

29. Making Hybrid Materials: Class 1E(Interpenetrating network) • Both organic and inorganic phases grow simultaneously • Timing is more difficult • Reproducibility is a challenge • May need to use crosslinking organic monomers to ensure solid product

30. Making Hybrid Materials: Class 2A(Covalent links at molecular level) • Organic group is attached to network at molecular level • Pendant or bridging monomers • Bridging groups can be small or macromolecule • This class also includes the organometallic polymers

31. Making Hybrid Materials: Class 2B(Covalent links at polymer level) • ligands attached to polymer • Reaction rates slow unless in sol. or melt

32. Making Hybrid Materials: Class 2C(Templating) Shown here with block copolymer Heat polymer then cool or cast from solvent

33. Classes 2D &E Covalent coupling agents Class 2D: Attaching organic group onto inorganic material Class 2E: Attaching inorganic group onto organic polymer For tough electrical wire coating & shrink fit wrapa

34. Have a nice week-end