Transcript Chemistry and Physics of Hybrid Materials

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