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

Nacre

Argonite (CaCO3) plates as inorganicwith protein (polyamide) as organic

Animals

Plants

phytolith

Teeth, spines in echindermsMussel shells, sponges, diatoms and corals are utilize hybrid organic-inorganic materials

Organic phase is biopolymers

Carbohydrates are the template and organic phase

Silica - SiO2

radiolaria diatoms

Colloidal silica in diatoms: Hierarchical structure

Silica walls are build up from ca. 5nm particles to give ca. 40nm diameter particles that are organized within the frustule.

pH ≈ 5

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: NacreArgonite (CaCO3) plates as inorganic phasewith 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

Barthelat F Phil. Trans. R. Soc. A 2007;365:2907-2919

argonitecrystalstructure

Phasemorphology

Long range order: stacked crystals

Growth rings (mesolayers)

Macromolecular

Inner surface of shell (mother or pearl)

The shell itself

Lobster exoskelton

CaCO3

& Carbohydrate & protein

Teeth: Enamel, dentin, and cementum

Apatite – hydrated CaPO4

Protein– collagen & others

200 MPa yield strength 30 MPaM0.5 toughness

Apatite – hydrated CaPO4

Protein– collagenBones

Echinoderm spine

CaCO3

Protein templating

Phytoliths

Horsetail, banana leaves

2-3% silicon by weight

SiO2 silica

Silica in Sponges

Bio Hybrid Organic-Inorganic MaterialsSophisticated, 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 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

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

Silica Particles

Preformed inorganic clusters

POSS

Inorganic PhasesCarbon 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)

•Porous metal oxide•Liquid monomer (no solvent) •UV, heat, radiation

Non-porous composite material

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 2E: Attaching inorganic group onto organic polymer

For tough electrical wire coating& shrink fit wrapa

Class 2D: Attaching organic group onto inorganic material

Have a nice week-end