synthesis of phthalonitrile-containing siloxane polymers for use in
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1
Synthesis of Phthalonitrile-Containing Siloxane Polymers for Semiconductor Power ModulesNOAH GRIGGS1, JACOB MONZEL2, AND DR. GORDON YEE1
1 VIRGINIA TECH DEPARTMENT OF CHEMISTRY2 VIRGINIA TECH DEPARTMENT OF MATERIAL SCIENCE & ENGINEERING
2Phthalonitriles
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
3Current state of Phthalonitriles
Similar properties to polyetheretherketone (PEEK) polymers
Brittle once the thermosetting is complete
Insoluble in most organic solvents
4Improving 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
5Objectives
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
Si O SiHO OH
6Preparation 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
SiCl Cl +O
Br
O Si Cl
A) n-BuLiB) Mg, THF
7Preparation of Disiloxane
The chlorosilane product is air sensitive, and when exposed to moisture forms the disiloxane
O Si Cl Si O SiO O
A) H2O, RT B) NaOH, H2O, HeatC) DMF
8Cleavage of Protecting groups
The protecting groups were cleaved via acid to produce the target disiloxane
Si O SiO O Si O SiHO OH
A) Pd/C, H2B) Pd/C, Ph2S, H2C) H+ , EtOH
9Polymer Synthesis
Determination of optimal reaction conditions via reaction of disiloxane with nitrophthalonitrile
Si O SiHO OH
NO2
CN
CN
Si O SiO O
NC
NC
CNNC
K2CO3,DMF
10Polymer Synthesis
Extending the length of the monomer
Si O SiHO OH
CN
CN
O
OCl
Si O SiO O
O O
CNNC
OO
NCCN
NaOH, K2CO3,DMF
11Polymer Synthesis
Synthesize the final polymer via reacting the disiloxane with dichlorobenzene and 4-(4-hydroxyphenoxy)phthalonitrile under basic conditions in DMF
Si O SiHO OH
CN
CNO
HO
Cl ClSi O SiO O
O O
CNNC
OO
NCCN
NaOH, K2CO3,DMF
12Results
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
13NMR Results
Starting Material
ProductSi O SiO O
14Mass Spectrometry Results
15Conclusion
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
16Future 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
17Acknowledgements
National Science Foundation Virginia Polytechnic Institute and State
University, Macromolecules Innovation Institute, and Department of Chemistry
Dr. Gordon Yee, Jacob Monzel, and Chris Houser