Synthesis of Phthalonitrile-Containing Siloxane Polymers for use in
1. Synthesis of Phthalonitrile-Containing Siloxane
Polymers for Semiconductor Power Modules
NOAH GRIGGS1, JACOB MONZEL2, AND DR. GORDON YEE1
1 VIRGINIA TECH DEPARTMENT OF CHEMISTRY
2 VIRGINIA TECH DEPARTMENT OF MATERIAL SCIENCE & ENGINEERING
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2. Phthalonitriles
Candidates for high-temperature polymers
Strong up to 500 ˚C, easily processed, and
nearly fireproof
Replacement for metal in sections of
turbine engines
Encapsulation compound for
semiconductor power modules
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3. Current state of Phthalonitriles
Similar properties to polyetheretherketone
(PEEK) polymers
Brittle once the thermosetting is complete
Insoluble in most organic solvents
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4. Improving Phthalonitriles
Incorporating thermally stable, flexible linkages in
backbone of polymer
Lowers softening point
Improves solubility
Does not sacrifice the properties of the cured material
Recent interest in incorporating silicon-based
linkages
Siloxane polymers are both thermally stable and
flexible
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5. Objectives
Design synthesis route for 1,3-Bis(p-hydroxyphenyl)1,1,3,3-
tetraphenyldisiloxane
Form the phthalontrile linkages
Polymerize the disiloxane to synthesize the polymer
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6. Preparation of Disiloxane
Reaction of dichlorodiphenylsilane with 4-benzyloxybromobenzene
Formation of reactive Grignard
1:1 stoichiometry
Prevention of unwanted side reactions via a benzyl protecting group
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A) n-BuLi
B) Mg, THF
7. Preparation of Disiloxane
The chlorosilane product is air sensitive, and when exposed to moisture
forms the disiloxane
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A) H2O, RT
B) NaOH, H2O, Heat
C) DMF
8. Cleavage of Protecting groups
The protecting groups were cleaved via acid to
produce the target disiloxane
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A) Pd/C, H2
B) Pd/C, Ph2S, H2
C) H+ , EtOH
11. Polymer Synthesis
Synthesize the final polymer via reacting the disiloxane with
dichlorobenzene and 4-(4-hydroxyphenoxy)phthalonitrile under basic
conditions in DMF
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NaOH,
K2CO3,
DMF
12. Results
Characterization conducted via H1 NMR and ESI TOF
Mass Spectrometry
Low yields with Grignard synthesis of disiloxane
Side products formed in greater yield than desired
product
Isolation of desired product difficult due to the
chemical similarity of side products
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15. Conclusion
Most likely high purity reagents and extremely low
moisture environments are required to achieve viable
yields using the Grignard method
Low yields may be due to compromised glove box
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16. Future Work
Use of halogen-lithium exchange to form the
reagent instead of magnesium
Testing the properties of the phthalonitrile-
linked siloxane polymer
Formation of phthalocyanine rings via
reacting the phthalonitrile end groups with
Lithium metal
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17. Acknowledgements
National Science Foundation
Virginia Polytechnic Institute and State University,
Macromolecules Innovation Institute, and
Department of Chemistry
Dr. Gordon Yee, Jacob Monzel, and Chris Houser
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Editor's Notes
What do Phthalonitriles have to do with semiconductor power modules? Moreover what do power modules have to do with the nexus of food-water-energy that is the main focus of the presentations today?
Current semiconductors are encapsulate in epoxy resins
Good adhesive, so release agents are required
Flammable, so fire retardant additives are required
Leads to increased costs
Phthalonitriles offer excellent retention of electrical and mechanical properties at elevated temperatures
Good for coating and encapsulating power modules
Widely found in inverters for renewable energies
Including wind turbines, solar cells and tidal power plants
Also the heart of an electric vehicle’s power plant and some industrial machines
The semi-conductor power modules require high-temperature polymers as encapsulation compounds; the polymer acts as an insulator of both heat and electricity. Low coefficient of thermal expansion, so low chance to damage the electrical components
Naval research lab
High temp thermoset
Replace metals in cooler sections of turbine engines
Encapsulation polymer
Similar to PEEK in that they are lightweight and temperature resistant
Left: PN resin uncured
Right: cured PN resin
Siloxanes are UV-stable
can be used in solar cells without worry of degredation
In order to prevent unwanted side reactions we used benzyloxy bromobenzene which has a benzyl protecting group
React disiloxane with dichlorobenzene and hydroxyphenoxyphthalonitrile to form final polymer
Low yields possibly due to leak in glove box: unfortunate; but that could explain why the Grignard did not react with the dichlorodiphenylsilane
Which could have reacted with itself and water to form siloxanes with hydroxyl caps that would not react with the grignard
