Warren Solfiell McCarley Research Group Department of Chemistry Louisiana State University

1. Analytical and structural evaluation of poly(3-hexylthiophene)s formed by chemical oxidative coupling methods: the role of experimental conditions in their design Warren Solfiell McCarley Research Group Department of Chemistry Louisiana State University Baton Rouge November 16 2009

2. Capture and release dendrimers Oligomerized monomer units Reducing agent Oxidative coupling Pyrrole Monomer capped dendrimer DAB-(Py)32

3. Oxidation of poly(pyrrole)s for capture and release oxidized reduced

4. Heterocyclic Conducting Polymers

5. Field Effect Transistors • Oganic/biological sensors • OLEDs • Flexible Displays • Solar Cells • Antistatic • Printable conductive ink • Anti-corrosion • RFID tags

6. Polymerization procedure for chemical oxidative coupling 1.00 mmol of monomer in 12.5 mL solvent used (80 mM) quench with MeOH 24 hours stir 1 hour (@RT) under argon 1.00 mmol of FeCl3 in 12.5 mL solvent used (80 mM) then washed and extracted with 300 mL 2.0N HCl and 200 mL chloroform chloroform is rotary-evaporated and polymer film is dried under high vacuum to constant mass solid polymer is filtered off

7. Oxidation pathway for heterocyclic conducting polymers oligomerization

8. OVERVIEW • OBJECTIVE • Tailor characteristics of polymer formed by chemical oxidation • 1. Regio-regularity • 2. Molecular weights • 3. Polydispersities • 4. End-group additives • Controlling experimental parameters • 1. Solvent system • 2. Temperature • 3. Time • 4. Oxidant/catalyst

9. Matrix-assisted laser desorption and ionization (MALDI) Figured adapted from; www.psrc.usm.edu/ mauritz/images/maldi2b.jpg

10. MALDI- Time of flight (Tof) Mass spectrometry Figure adapted from; Dass, C. Principles and Practice of Biological Mass Spectrometry; Wiley-Interscience: New York, 2001.

11. MALDI- Time of flight (Tof) Mass spectrometry Mend = Mpeak - Mcat - nMrep Mend = Mpeak - Mprot - nMrep Mend = Mpeak - Melec - nMrep [M].+

12. Size exclusion chromatography (SEC) figures adapted from; http://content.answers.com/main/content/img/McGrawHill/Encyclopedia/images/CE283900FG0010.gif and http://www.sci.sdsu.edu/TFrey/Bio750/Chroma4.gif

13. Part One: Modifications to polymerization procedures for chemical oxidative coupling of poly(3-hexylthiophene)s

14. Matrix assisted laser desorption and ionization (MALDI) matrices

15. MALDI spectra P3HT made in chloroform -Top spectra terthiophene matrix -Bottom spectra DCTB matrix

16. MALDI spectrum P3HT made in nitromethane with 1:2.5 monomer:oxidant ratio terthiophene matrix

17. MALDI spectra solid P3HT made in nitromethane DCTB matrix spectrum

18. spectrum MALDI spectra soluble P3HT made in nitromethane DCTB matrix

19. 1H-NMR P3HT made in nitromethane -soluble fraction above -Solid precipitate below 26% 67%

20. Conclusions-Part One DCTB, a previously unreported matrix for use with poly(alkylthiophene)s, is preferable and beneficial for MALDI analysis of these materials Soluble material from the chemical oxidative coupling polymerization of these materials is not useful product Decreasing the monomer to oxidant ratio for these polymerizations does reduce the chlorine addition to these materials but does not produce only hydrogen terminated product Ion discrimination does occur during MALDI ionization between chlorinated and non-chlorinated oligomers which is dependent on the extent of halogenation Sample preparation and choice of matrices is crucial

21. Part Two: Characterization of effects to the physical properties of poly(3-hexylthiophene)s made by chemical oxidation at low-temperatures

22. MALDI spectra solid P3HT made in nitromethane @ room temperature DCTB matrix spectrum

23. MALDI spectra solid P3HT made in nitromethane @ - 30 ºC DCTB matrix spectrum

24. MALDI spectra solid P3HT made in chloroform @ room temperature DCTB matrix spectrum

25. spectrum MALDI spectra solid P3HT made in chloroform @ - 30 ºC DCTB matrix

26. 1H-NMR comparisons of room temperature and low-temperature polymerizations Nitromethane Chloroform A B C D 51% 78% 77% 65%

27. Equation 1 2FeCl3 FeCl2+ +FeCl4¯ Equation 2 2FeCl3 Fe2Cl5+ + Cl¯ Conclusions-Part Two Shift in equilibrium between active species (Fe2Cl5+ /FeCl2+ ) could be attributed to reduced chlorination as the result of several factors FeCl3 becomes more soluble during these low-temperature polymerizations Dielectric constant slightly increases Reaction time increases (from 1 to 24 hours) Low temperature slows kinetics of reaction Regio-regularity only slightly improves for certain solvents Still a random event Radical lifetimes are dependent on solvent and prolonged with reduced temperature Oxidation potentials are reduced as oligomer chain grows and oligomer-oligomer coupling may be preferable for certain solvents regardless of temperature

28. Part Three: Characterization of solvent effects on polymerization and physical properties of poly(3-hexylthiophene)s made by chemical oxidation

29. Solvents employed for solvent effect studies

30. MALDI spectra solid P3HT made in 1, 2-dichloroethane @ room temperature; DCTB matrix spectrum 1,2 -dichloroethane ɛr = 10.4 An = 100 * Dn = negligible Yield = 25% (45 mg) 1H-NMR of P3HT made in 1,2-dichloroethane at room temperature 81% regio-regular

31. spectrum MALDI spectra solid P3HT made in acetonitrile @ room temperature; DCTB matrix acetonitrile ɛr = 36.6 An =19.3 Dn =14.1 Yield = 27% (46 mg) 1H-NMR of P3HT made in acetonitrile at room temperature 75% regio-regular

32. spectrum MALDI spectra solid P3HT made in nitrobenzene @ room temperature; DCTB matrix nitrobenzene ɛr = 35.7 An = 14.8 Dn = 4.4 Yield = 13% (21 mg) 1H-NMR of P3HT made in nitrobenzene at room temperature 67% regio-regular

33. Comparison of number average (Mn) molecular weights from SEC

34. Comparison of polydispersities from SEC

35. Equation 1 2FeCl3 FeCl2+ +FeCl4¯ Equation 2 2FeCl3 Fe2Cl5+ + Cl¯ Conclusions-Part Three Solvents with strong Lewis basicity (large Donor number) complex the active species of oxidant disabling active species interaction with monomer Degree of polymerization may depend more on active species interaction with solvent than monomer Large dielectric constants (i.e. solubility) is not the only reason for presence of tetrachloroferrate ion (as is the case with acetonitrile) Appears as though solvents with large dielectric constants and with strong Lewis acidity (large Acceptor number) shift equilibrium to tetrachloroferrate population Solvent plays a large role in lifetimes of ionic species i.e monomer, dimer , trimer etc. influencing polymer growth and therefore regioregularity Solvent also influences coupling rates reflected in regioregularity

36. Part Four: Semi-preparative size exclusion chromatography for the fractionation of poly(3-hexylthiophene)s made by chemical oxidation

38. 1H-NMR spectra of toluene fractions collected from semi-prep GPC Fraction 1 - 77% Fraction 3 - 77%

39. 1H-NMR spectra of toluene fractions collected from semi-prep GPC Fraction 4 - 77% Fraction 6 - 68%

40. 1H-NMR spectra of toluene fractions collected from semi-prep GPC Fraction 7 - 62% Fraction 8 - 55%

41. UV-Vis spectrum of toluene fractions from semi-prep GPC

42. Conclusions-Part Four Appears to be different structures or states of polymer as represented by interactions of analyte with gel permeation column Semi-preparative fractionation seems to be able to effectively separate analyte for molecular weight and structural studies with some modification to procedure Evidence of change in regularity for different molecular weights which makes sense as larger polymer should be more regular material Procedure may enable obtaining more desirable product made through chemical oxidative coupling polymerization

43. Future Work Experiments to further confirm shifts of active species dependent on solvent and temperature Examine fractions obtained from semi-preparative GPC with MALDI for clarification of species or reasons for different interactions with GPC column Use fractions from semi-preparative GPC in order to further separate individual oligomers, greater than n = 14, in large enough quantities to investigate thoroughly using HPLC

44. Acknowledgements • Prof. Robin L. McCarley • McCarley Research Group • Dr. Rebecca Brauch • Dr. Rafael Cueto • Dr. Evgueni Nesterov • Dr. Azeem Hasan • Dr. Dan Pu • Dr. Kermit Murray • Louisiana State Economic Development Asst.