1. Silica-Like Malleable Materials
Group 10
Kristen Losensky
Tzu-Hao Yen

2. Summary: How It Works Thermoplastics
Flow when heated
Can be extruded shaped and molded
Thermosetting / Cross-linked Polymers
Can not be reprocessed by heat or solvent
Dimensional stability
High-temperature mechanical, thermal, and environmental resistance
Make covalent links reversible
High Temperature: exchange reactions enable stress relaxation and malleability
Low Temperature: exchanges become essentially stop, producing a solid system
Reversible topology fixing controlled by kinetics
Preserve Network Integrity/Total # of Links/ Avg Functionality of X-Links/ Does not require Depolymerization
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov

3. Summary: Research Performed
Synthesis of both hard and soft epoxy networks with rearrangable topology
Exchange reactions without depolymerization.
Insoluble and processable
Gradual viscosity variations
Examination of thermal and mechanical properties

4. Thermosetting Polymers
Thermosetting materials
Irreversible
Liquid prior to curing
Good mechanical properties
Solvent resistant
Cured by heat and radiation
Example = Bakelite  suitable for electrical industries because of its resistance to heat and chemical reaction, used for non-conducting parts, also used for wire insulation, brake pads.

5. Cross-Linked Materials
Cross-linking
Un-polymerized resin + Crosslinking agents
Difficult to break
Most materials when heated may degrade or burn
Commercial plastics

6. Thermoplastic Polymers
Thermoplastic materials
Reversible
Remold and reforms
Weaker mechanical properties
Solvent soluble
Recyclable
Acrylontrile butadiene styrene = lego blocks
Polycarbonate = eyeglass lenses

7. Reversible Malleable Material Issues
Depolymerization-repolymerization equilibria
Degradation of combined materials
Unavoidable termination reactions

8. High Silica Materials Amorphous silica Thermally insulated
Inert to chemical reagents
Resistance to organic acids
Electrical insulation
Easily molded

9. Stress & Strain Diagram
Will explain each point during presentation

10. Previous Work Radical Systems Chemical Equilibrium
Photoinduced plasticity in cross-linked polymers
Thermally/ Photochemically induced reparability
Unavoidable Termination Reactions
Chemical Equilibrium
Heating
Drives equilibrium towards depolymerization
Increases rate of bond breaking/reforming
Prevent flow by using glass transition
Increased fluidity and processability
Network is less stable and sensitive to solvents
(Undesirable Termination Limits reversibility) (Solvents displace equilibrium)
molle.k.u-tokyo.ac.jp

11. Materials and Methods Soft Networks
Fatty acids and Catalyst Zn(Ac)2, 2H2O heated from 100 °C to 180°C under vacuum
Diglycidal ether of bisphenol A (DGEBA) is added to fatty acid mixture and stirred at 130°C
Mixture is poured into brass mold with anti-adhesive silicone paper
COOH : epoxy is 1:1

12. Materials and Methods Hard Networks
Zinc Acetylacetonate Dihydrate Catalyst dissolved in DGEBA by heating
Glutaric Anhydride added
Poured into brass mold
Cured at 140°C for 12 h

13. Results: Soft Network Synthesis
DGEBA and fatty dicarboxylic and tricarboxylic acids
Epoxy/COOH has 1:1 stoichiometry
Zinc Acetate Catalyst Zn(Ac)2
Complete conversion of epoxy groups
Transesterification Reactions
Want both OH and Ester groups in final material -> Exchange reactions = transesterification reactions
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov

14. Results: Soft Network Properties
Elastomeric behavior
Modulus of 4 MPa
Elongation and stress at break 180%, 9 MPa
Number of ester links does not change with heating
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov

15. Results: Soft Network Solubility
The network swells but does not dissolve
Fig. 2 Flow and insolubility properties of an epoxy network with 5 mol% Zn(Ac)2 catalyst. (A)Swelling during immersion in trichlorobenzene
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov

16. Results: Soft Network Malleability
Can completely relax stresses at high temperatures
η(T) follows Arrhenius law
100 °C relaxation time of 58 h
Room temperature relaxation time of 6 yr
Can easily make complex shapes without mold
(Activation Energy = 80 kJ/mol K) (B=Normalized stress relaxation at different T)
b/c n does not change abruptly, do not need precise T control -> more manufacturing options
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov

17. Results: Hard Network Synthesis
DGEBA with glutaric anhydride
Zinc Acetyl Acetonate Zn(AcAc)2
Epoxy/Acyl stoichiometry is 1:1
Transesterification Reactions
Resins made by Epoxy-Anhydride reactions
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov

18. Results: Hard Network Solubility
Sample swells but does not dissolve
16 h in trichlorobenzene at 180 °C
Number of ester links does not change with temperature
Network does not polymerize even after a long t and at high T
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov

19. Results: Hard Network Properties
Behavior is similar to typical hard epoxy resins
Glass Transition Tg 80 °C
Modulus of 1.8 GPa
Stress at break of 55 MPa
Transesterification reactions allow network to flow
Viscosity of 1.2 x 1010 Pa s
η(T) follows Arrhenius equation
(200C Elongational Creep expt) (10 mol% catalyst) (deformation varies linearly w/time, n from slope) (Ea = 88 kJ/mol K)
A=Tensile Test
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov

20. Results: Hard Network Malleability
Can be reprocessed
Compression molding at high temperature
3 min at 240 °C
Can form complex shapes without molds
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov

21. Results: Topology
Systems with exchangeable links behave as a viscoelastic fluid
Above Tg exchange reactions occur slowly
Material properties depend on thermal history
During cooling ramp:
Topology rearrangements become too slow, network appears quenched
Further cooling freezes local monomer motion
highT) (polymer melts flow properties by monomer friction) (freeze monomer motion = Tg)
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov

22. Results: Dilatometry Experiments
Cross-linked polymers have lower expansion coefficients
Increasing catalyst concentration increases expansion coefficients
Topology freezing is well separated from Tg
Topology freezing and Tg shift to higher temperatures when the heating rate is increased
(more catalyst -> faster rxns)
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov

23. Results: Broadness of Tg
Rate of change of η at Tg
“Strong” Glass Formers show broad Arrhenius-like variations
Silica
P2O5
“Fragile” Glass Formers show rapid η increase upon cooling
Organic and Polymer liquids
(epoxy-acid networks Tg C for mol %)
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov

24. Assessment
Synthesized both soft and hard polymer networks with reversible covalent links
Transesterification Reactions
Mechanical Properties
Insoluble
Arrhenius-like variation in viscosity
Separate topology freezing and glass transitions
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov

25. Further Research
Ability to control or fine tune temperature of topology freezing transition
Ability to control or fine tune glass transition temperature
Choice of starting materials

26. References (Pictures)
molle.k.u-tokyo.ac.jp

27. References
Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): Web. 11 Nov
Callister, William D., and David G. Rethwisch. Fundamentals of Materials Science and Engineering: An Integrated Approach. Hoboken, NJ: Wiley, Print.

28. Questions?