Screening for New Materials Synthesis Aaron Baldwin, Robert Lerrinzini, Whitney Kline,

1. Screening for New Materials Synthesis Aaron Baldwin, Robert Lerrinzini, Whitney Kline, Gregory Sotzing University of Connecticut/AFRL RYDP ONR Capacitor Materials Program Review March 7, 2012

2. Three Directions/Sub-projects Screening for new materials Exploration of the polymer chemical space High-throughput DFT calculations QSPR – Polymer Informatics Parallel synthesis work Ramprasad, Breneman, Sotzing Morphology & functionalization Morphology predictions Optimization of PP-OH polymers The role of OH functional groups Processing & characterization Kumar, Chung, Weiss (& Boggs, Ramprasad) Breakdown & aging Intrinsic breakdown Role of extrinsic factors (defects, disorder) Aging Multi-scale & statistical treatment Boggs, Ramprasad (& Kumar, Weiss)

3. Role of the Sotzing Group Be guided by the theoreticians of the group to prepare new polymers • Theoretician will propose a structure or partial structure based upon their calculations • Extensive literature research is carried out to see if the polymer has ever been made • If the structure has never been made, we propose pathways by which to make it • If there is no literature that helps us in the proposed pathway or alternate pathways we find a structure that is a close fit that is realistic to make with input of usefulness from theoretician. Prepare New Polymers • Preparation of monomers and their purification/characterization • Preparation of polymers and their purification/characterization • Prepare films of the polymers for impedance measurement Provide feedback to the theoreticians with respect to the data on the polymer for second iteration

4. “2nd Round” Results (Ramprasad) Second Round building blocks: -XY2- (X=C, Si, Ge, Sn and Y=H, F, Cl, CH3, CF3)

5. Silicon Polymers Feed from Theorist: Predicted to have high dielectric constants based upon polarizability The smaller the groups attached to the Si backbone, the better Hydrogen is preferred, Fluoride is understood to be better Practical Considerations: Si-H bonds are hydrolytically unstable (Polysilane - John et al. JCS Chem. Commun, 1983, p. 1496) Polymer with solely F has not been prepared According to one report, Si-F bonds are hydrolytically unstable (within this study a Si version of polyvinylidene fluoride was prepared, Interrante, et al. J. Am. Chem. Soc., 1997, 119 (49), 12020–12021) Polysilanes with alkyl groups can be made via Wurtz coupling. Those polysilanes that have been made have not been tested for capacitor application

6. PolySilanes Synthesis Poly(dimethylsilane)*: R=Me, R’=Me Poly(di-n-octylsilane)#: R=Oct, R’=Oct Poly(di-n-butylsilane)#: R=Bu, R’=Bu Poly(phenylmethylsilane)#: R=Ph, R’=Me Poly(diphenylsilane)*: R=Ph, R’=Ph Various copolymers of R,R’ = Me : R=Me, R’=Ph Extensive Soxhlet purification Film spin cast on steel shim 130 ppm Na by Atomic Absorption Resistance: 9 kW *Insoluble Polymers # Limited Solubility

7. Parallel Effort, Segmented Conjugation

8. Band Gaps Ar =

9. Polymer Properties For higher band gap polymers, cannot get Li amounts below 150 ppm

10. Summary for PolySilanes – Lessons Learned Band gaps can be 4 eV or above (with segmentation) Na and Li salts produced as by-product can not be purified below 150 ppm • Polymers will retain some water – so there will be ionic conductivity • Conductivity, as a result, is approximately 9-10 kW • For the future • Do polymerizations that produce volatile side products or no side product • Metal catalyzed polymerizations (like for PP) • Ring opening polymerizations • Step Growth/Addition (isocyanates) • Cycloadditions (Diels-Alder) • Only a limited number of condensation-type polymerizations

11. Germanium Polymers Ramprasad, UCONN Upon inspection – others are either 1. Too low of a band gap 2. Too reactive 3. Too exotic 4. Unable to be made The one circled we might have a shot, but it has never been made. High risk, potentially high pay-off

12. Proposed Routes to Germanium Polymer Proposed synthesis is based on routes published for Si analogues Good news – Si is much more reactive than Ge

13. 1,1,3,3-tetraethoxy-1,3-disilacyclobutane • 1,1,3,3-tetraethoxy-1,3-disilacyclobutane has been synthesized • Elemental analysis within 1% of theoretical results. 1 Interrante, L. V.; Liu, Q.; Rushkin, I.; Shen, Q.; J. Organomet. Chem., 1996, 521, 1-10.

14. Next Step, Polymerization • Route 1 • 70% yield for the first step • Reduced molecular weight • Route 2 • Fully fluorinated polymer can be obtained by fluorination but only with exclusion of atmospheric moisture (i.e. reaction performed in a glove box) • Higher molecular weight than route 1, GPC analysis done on the reduced ethoxy polymer. GPC measured ~130 repeat units. Catalyst breaks the Si-C bond. 2 Lienhard, M.; Rushkin, I.; Verdecia, G.; Wiegand, C.; Apple, T.; Interrante, L.V.; J. Am. Chem. Soc., 1997, 119, 12020-12021

15. 1,1,2,2-tetraethoxy-1,2-disilacyclobutane3,4 This is a version of Gusel’nikov’s cyclization reaction in which he cyclizes the methyl instead of the alkoxy to form 1,1,2,2-tetramethyl-1,2-disilacyclobutane. This is Ando’s version of the cyclization starting from the alkene. 3 Gusel’nikov, L. E.; Polyakov, E. A.; Volnina, E. A.; Nametkin, N. S.; J. Organomet. Chem., 1985, 292, 189-203. 4 Kusukawa, T.; Kabe, Y.; Nestler, B.; Ando, W.; Organometallics, 1995, 14, 2556-2564.

16. Proposed Routes to Germanium Polymer Proposed synthesis is based on routes published for Si analogues Good news – Si is much more reactive than Ge

17. Part II ‘Organic Polymers’

18. Functional Groups with High Ionic Polarizabilities Breneman, Sukumar (RPI) Upon reviewing their ‘shortlist’ of potentials, the best candidates were urethanes, ureas, and imides

19. “3rd Round” Results, Ramprasad Third Round building blocks: -CH2-, -NH-, -CO-, -C6H4-, -C4H2S-, -CS-, -O-

20. Monomers for Organic Polymers Polyimides Polyureas Polyurethanes Have made 10 of the 14 polymers proposed here

21. Rationale Utilize the functionalities calculated by Sukumar and Breneman to prepare the leanest polymers possible (most functionality) while retaining processability. Higher thermal stability than polyureas or polyurethanes Can be processed from polyamic acid, water evolved Only impurities would be solvent and water No by-product produced Only use the two monomers for polymerization – no solvent needed Polymerization very fast No by-product produced Use two monomers for polymerization – no solvent needed, Sn catalyst used Polymerization slower than that for the polyurea

22. RECENT PUBLICATIONS, PATENTS, AWARDS • Publications: • None yet • Manuscript in Preparation on Silane polymers. Synthesis funded by ONR, electrochromics funded by Alphachromics, Inc. “Color Tuning of Black for Electrochromics using Polymer Precursor Blends”, to be submitted to Advanced Materials.

23. Navy Relevance and Impact • Downselection of thousands of relevant targets for better capacitor materials as anticipated by theorists to a small subset of polymers that can be realistically made, and made with the purity required for this application. • Understand the limitations of synthesis on making these materials • Compare the properties of the as-made polymers with the calculations, try to understand deviations in theory to practice and refine the structure through further calculation. • The goal is to potentially find a material that could be more efficient than PP or find a class of materials that could potentially fulfill this goal. • Broader Impacts: • Some materials being explored in combination with conjugated polymers for variable capacitors (varactors) at AFRL RYDP … results are promising • Black electrochromics being incorporated into goggle and spectacle variable light transmission (VLT)s for military protective wear.