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Chemistry and Physics of Hybrid Materials Lecture 2 Today • Quiz #1 • Biohybrids • Tools for making hybrids Hybrid Organic-Inorganic materials are common in nature: composites Animals Nacre Organic phase is biopolymers Plants 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 phytolith Carbohydrates are the template and organic phase Silica - SiO2 radiolaria diatoms 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. What is a hierarchical structure? In materials, a structure with different structures at different length scales: like in tendons (above) More Bio-Hybrids based on CaCO3: Nacre Argonite (CaCO3) plates as inorganic phase with protein (polyamide) as organic phase Mother-of-pearl Opalescence from light diffraction in nacre (argonite blocks height ≈ λ light) Fracture strength is 3000 times higher than its mineral constituent CaCO3. The hierarchical structure of nacre The shell itself Growth rings (mesolayers) Inner surface of shell (mother or pearl) Macromolecular Phase morphology Long range order: stacked crystals Barthelat F Phil. Trans. R. Soc. A 2007;365:2907-2919 argonite crystal structure Lobster exoskelton CaCO3 & Carbohydrate & protein Teeth: Enamel, dentin, and cementum Apatite – hydrated CaPO4 Protein– collagen & others Apatite – hydrated CaPO4 Protein– collagen 200 MPa yield strength Bones 30 MPaM0.5 toughness Echinoderm spine CaCO3 Protein templating Phytoliths SiO2 silica 2-3% silicon by weight Horsetail, banana leaves Silica in Sponges 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 Making hybrids ourselves Class 1 Hybrids: No covalent bonds between organic & inorganic phases Class 2 Hybrids: Covalent bonds between organic & inorganic phases Life uses Class 2C approach to make biohybrids 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) 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 For example: Physical hybrids Class 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 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. Inorganic Phases Preformed inorganic clusters Silica Particles POSS Inorganic Phases Carbon Buckeyballs, nanotubes and graphene Nature Materials 9, 868–871 (2010) Making Hybrid Materials: Class 1A (pre-formed particles and fibers) Physical mixing or particles 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). Making Hybrid Materials: Class 1C (Polymerizing in pores) Non-porous composite materi •Porous metal oxide •Liquid monomer (no solvent) •UV, heat, radiation 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 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 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 Making Hybrid Materials: Class 2B (Covalent links at polymer level) • ligands attached to polymer • Reaction rates slow unless in sol. or melt Making Hybrid Materials: Class 2C (Templating) Shown here with block copolymer Heat polymer then cool or cast from solvent 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 Have a nice week-end