The Oligomer Approach
The discovery of optoelectronic properties analogous of PANI shown by aniline oligomers, such as tetra(aniline) (TANI) and octa(aniline) (OANI), has presented new opportunities to tackle the aforementioned issues.9,10,11 Recently, our group has reported preparation of thin films of phenyl/phenyl capped oligo(aniline)s in the emeraldine base (EB) and conducting emeraldine salt (ES) states following a drop‑casting method using THF as solvent.5,13 Amorphous films for oligo(aniline)s in the non‑conductive EB state were determinate by X‑ray studies. However, crystalline thin films for the same oligo(aniline)s in the fully doped conducting ES state were produced in the same fashion. The observed lamellar structure for films in the ES state has been attributed to the ionic‑interactions present between the dopant and the oligo(aniline) molecule.
Furthermore, this so‑called oligomer approach has demonstrated to be potentially useful for the understanding of optoelectronic properties of PANI. For example, a recent study of a range of TANI‑based molecules has provided important information to support a redox mechanism suggested for poly(aniline)s.14,15 To clarify the effect of minor modifications into their π‑conjugated backbone of phenyl/phenyl TANI on their optoelectronic properties differential pulsed voltammetry (DPV) and UV/vis investigations were performed. For instance, the electrochemical studies have provided experimental information to support an electron‑electron and electron‑chemical mechanism‑coupled reaction stated for the redox switching properties shown by aniline‑based materials. Besides, the UV/Vis absorption spectra obtained from THF solutions point to the possibility of tuning optical properties thought covalent modification of π‑conjugated oligo(anilines)s.
(9) Wang, Y.; Tran, H. D.; Kaner, R. B. Macromolecular rapid communications 2011, 32, 35–49.
(10) Wang, Y.; Liu, J.; Tran, H. D.; Mecklenburg, M.; Guan, X. N.; Stieg, A. Z.; Regan, B. C.; Martin, D. C.; Kaner, R. B. Journal of the American Chemical Society 2012, 134, 9251–9262.
(11) Wei, Z.; Faul, C. F. J. Macromolecular Rapid Communications 2008, 29, 280–292.
(12) Gmbh, C. W. V.; Sessler, J. L.; Sathiosatham, M.; Doerr, K.; Abboud, K. A. 2000, 1–9.
(13) Wei, Z.; Laitinen, T.; Smarsly, B.; Ikkala, O.; Faul, C. F. J. Angewandte Chemie (International ed. in English) 2005, 44, 751–6.
(14) Shao, Z.; Rannou, P.; Sadki, S.; Fey, N.; Lindsay, D. M.; Faul, C. F. J. Chemistry – A European Journal 2011, 17, 12512–12521.
(15) Heinze, J.; Frontana-Uribe, B. A.; Ludwigs, S. Chemical reviews 2010, 110, 4724–4771.