Jhe-Yong Lin (林哲永), Hui-Min Wang (王惠民), Sheng-Huei Hsiao (蕭勝輝)* Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, 1 Chunghsiao East Road, Section 3, Taipei 10608, Taiwan E-mail: [email protected] A novel class of electroactive polyimides with ether-linked anthraquinone (AQ) units were prepared from the polycondensation reactions of a newly synthesized CF3-containing AQ-dietheramine monomer with aromatic tetracarboxylic dianhydrides via a conventional two-step technique. The fluorinated polyetherimides (PEIs) exhibited enhanced solubility and optical transparency and decreased dielectric constants because of increased free volume caused by the CF 3 substituents. Furthermore, the PEIs showed high thermal stability, with glass-transition temperatures of 263-312 o C and decomposition temperatures in excess of 500 o C. These PEIs were also investigated by cyclic voltammetry and UV-visible spectroelectrochemistry. Preliminary results reveal that these AQ-based PEIs are potentially useful as cathodically coloring red electrochromes. Introduction References Results and Discussion 1. M. K. Ghosh, K. L. Mittal, Eds., Polyimides: Fundamentals and Applications. Marcel Dekker, New York, 1996. 2. J. de Abajo, J. G. de la Campa, Adv. Polym. Sci., 1999, 140, 23-59. 3. H.-J. Yen, G.-S. Liou, Polym. Chem., 2012, 3, 255-264. 4. E. M. Maya, I. Garcia-Yoldi, A. E. Lozano, J. G. de la Campa, J. de Abajo, Macromolecules, 2011, 44, 2780-2790. 5. Y. J. Cho, H. B. Park, Macromol. Rapid Commun. 2011, 32, 579-586. 6. J.-G. Liu, M. Ueda, J. Mater. Chem., 2009, 19, 8907-8919. 7. K. Fukukawa, M. Ueda, Polym. J. 2008, 40, 281-296 . 8. A. L. Rusanov, E. G. Bulycheva, M. G. Bugaenko, V. Yu Voytekunas, M. J. M. Abadie, Russ. Chem. Rev. 2009, 78, 53-75. 9. H.-J. Yen, C.-J. Chen, G.-S. Liou, Adv. Funct. Mater., 2013, 23, 5307-5316. 10. J. Q. Chambers, S. Patal, Z. W. Rappoport. The Chemistry of Quinonoid Compounds, Vol. II, Chap. 12, 1988. 11. A. Babaei, P. A. Connor, A. J. McQuillan. J. Chem. Educ., 1997, 74, 1200–1204. 12. R. M. F. Batista, E. Oliveira, S. P. G. Costa, C. Lodeiro, M. M. M. Raposo, Org. Lett., 2007, 9, 3201–3204. 13. E. H. van Dijik, D. J. T. Myles, M. H. van der Veen, J. C. Hummelen, Org. Lett., 2006, 8, 2333-2336. 14. S. Wang, E. K. Todd, M. Birau, J. Zhang, X.-H. Wan, Z.-Y. Wang, Chem. Mater., 2005, 17, 6388–6394. 15. W.-Q. Qiao, J. Zheng, Y.-F. Wang, Y.-J. Zheng, N.-H. Song, X.-H. Wan, Z.-Y. Wang, Org. Lett., 2008, 10, 641–644. 16. Y.-J. Zheng, J. Zheng, L. Dou, W.-Q. Qiao, X.-H. Wan, J. Mater. Chem., 2009, 19, 8470–8477. Scheme 1. Synthetic route to CF3-containing AQ-dietheramine 3 Figure 1. (a) 1 H NMR, (b) H-H COSY, (c) 13 C NMR and (d) C-H HMQC spectra of monomer 3 in DMSO-d 6 . A reversible color change takes place upon reduction (gain of electrons) or oxidation (loss of electrons). What is electrochromism ? Suitable electron acceptor Excellent electron mobility Spectroelectrochemistry S-H Hsiao,Y-R Kung. Polym. Int. 2013, 62, 573-580. S-H Hsiao, W-J Guo, C-L Chung, W-T Chen. Eur. Polym. J. 2010, 46, 1878–1890. Table 1. Inherent viscosity and solubility behavior of PEIs Polymer code a η inh (dL/g) b Solvents c,e PAA d Polyimide NMP DMAc DMF DMSO m- Cresol THF 5a-T 1.21 - -- -- -- -- -- -- 5a-C - -- -- -- -- -- -- 5b-T 1.01 - -- -- -- -- -- -- 5b-C - +- +- +- +- -- -- 5c-T 0.94 - -- -- -- -- -- -- 5c-C - ++ ++ ++ ++ +- -- 5’c-C - - +- -- -- -- -- -- 5d-T 0.89 - -- -- -- -- -- -- 5d-C - +- +- +- +- -- -- 5e-T 0.77 - +- +- +- +- +- +- 5e-C 0.51 ++ ++ ++ ++ +- ++ 5f-T 0.85 - -- -- +- -- -- -- 5f-C 0.76 ++ ++ ++ ++ +- ++ a T: polymer prepared by the thermal imidization method, C: by the chemical imidization method. b Inherent viscosity measured at a concentration of 0.5 dL/g in DMAc at 30 o C. c Solvent: NMP: N-methyl-2-pyrrolidone; DMAc: N,N-dimethylacetamide; DMF: N,N-dimethylformamide; DMSO: dimethyl sulfoxide; THF: tetrahydrofuran. d PAA: Poly(amic acid). e The qualitative solubility was tested with 10 mg of a sample in 1 mL of stirred solvent.++, soluble at room temperature; +, soluble on heating; +-, partially soluble; -, insoluble even on heating. Table 3. Optical properties of the PEIs Polymer code Film thickness (μm) Color coordinates b λ 0 (nm) c λ at 80% transmission (nm) a* b* L* Imidization method a (T) (C) (T) (C) (T) (C) (T) (C) (T) (C) (T) (C) Blank - -0.6 0.3 96.5 - - 5a - - - - - - - - - - - - 5b 47 - 20.7 - 66.2 - 64.4 - 429 - 539 - 5c 43 - 12.4 - 52.3 - 75.9 - 425 - 539 - 5d 44 - 7.3 - 43.1 - 75.2 - 423 - 537 - 5e 48 42 5.8 -3.8 30.3 26.7 82.3 84.5 417 423 521 473 5f 43 47 1.3 -3.2 36.0 22.1 80.8 85.6 425 425 506 468 Kapton 41 - 2.0 - 99.7 - 81.0 - 462 - 534 - 5’f - 45 - 12.3 - 57.1 - 64.5 - 490 - 580 a T: polymer prepared by the thermal imidization method, C: by the chemical imidization method. b The color parameters were calculated according to a CIE LAB equation. L* is the lightness, where 100 means white and 0 implies black. A positive a* means a red color, and a negative a* indicates a green color. A positive b* means a yellow color, and a negative b* implies a blue color. c Absorption edge from the UV–vis spectra of the polymer thin films. 5f-C 5’f-C Table 2. Thermal properties of PEIs Polymer code a T g ( o C ) b T d at 5 % weight loss ( o C ) c T d at 10 % weight loss ( o C ) c Char yield N 2 Air N 2 Air (wt %) d 5a 312 513 507 558 535 54 5b 289 565 557 595 587 56 5c 275 545 540 577 571 53 5d 263 547 541 580 574 53 5e 276 451 493 492 521 50 5f 281 536 531 557 552 51 5’f 285 565 549 592 578 56 a All the polymer films were heated at 300 o C for 1 h to DSC and TGA experiments. b Midpoint temperature of the baseline shift on the second DSC heating trace (rate= 20 o C/min) of the sample after quenching from 400 to 50 o C (rate= 20 o C/min) in nitrogen. c Decomposition temperature at which a 10% weight loss was recorded by TGA at a heating rate of 20 o C/min. d Residual weight % at 800 o C at a scan rate 20 o C /min in nitrogen. Figure 2. TGA and DSC curves of PEI 5c at a heating rate of 20 o C/min. 5g Figure 3. Cyclic voltammograms of model compound 5g (1x10 -3 M) in 0.1 M Bu 4 NClO 4 / DMF at a scan rate of 100 mV/s. Basic Properties Thermal Properties Optical Properties Electrochemical Properties Table 4. Redox potentials and energy levels of PEIes Code Thin film (nm) Reduction potential (V) Bandgaps (eV) λ max abs λ onset abs E onset Red E 1/2 Red,1 E 1/2 Red,2 E 1/2 Red,3 E 1/2 Red,4 E 1/2 Red,5 E g opt 5a 341 365 -0.64 -0.71 -1.19 3.40 5b 340 364 -0.59 -0.68 -1.03 -1.22 3.41 5c 336 359 -0.60 -0.68 -0.81 -1.10 -1.28 -1.64 3.45 5d 339 362 -0.54 -0.69 -1.15 -1.31 3.43 5e 353 382 -0.52 -0.65 -0.81 -0.99 -1.29 3.25 5f 348 393 -0.46 -0.66 -1.01 -1.13 3.16 5g - - -0.60 -0.65 -1.25 - Experimental Abstract Polym. Eng. Sci. 2008, 48, 2224. E. S. Lee et al. Sol. Energy Mater. Sol. Cells, 2002, 71, 465. www.gentex.com H-M Wang, S-H Hsiao. JPSA. 2011, 49, 337-351. http://www.siemens.com http://wwwf.imperial.ac.uk Himnos y Marchas Militares Vol.1 S-H Hsiao,Y-R Kung. Polym. Int. 2013. 62, 573-580. Spectroelectrochemistry (b) (c) (d) Figure 4. Cyclic voltammograms of the cast films of PEIs (a) 5a, (b) 5b, (c) 5c, (d) 5d, (e) 5e and (f) 5f in 0.1 M Bu 4 NClO 4 / DMF at a scan rate of 50mV/s. (e) (f) (c) (b) (a) (d) (a) Table 5. Electrochromic properties of PEI 5d Polymer λ max a (nm) Δ%T Response time b ΔOD c Q d d (mC/cm 2 ) CE e (cm 2 /C) t c (s) t b (s) 5d 563 36 5.0 7.9 0.199 1.74 114 Figure 6. Potential step absorptiometry of the cast film of 5d on the ITO-glass slide (coated area: 1.0 cm 2 )(in DMF with 0.1M Bu 4 NClO 4 as the supporting electrolyte)by applying a potential step (a) 5d at potential 0.0 V ~ -1.25 V and cycle time 12 s, and (b) optical switching for 5d at λ max = 563 nm as the applied voltage was stepped between 0.0 V and -1.25 V (vs. Ag/AgCl). a Wavelength of absorption maximum. b Time for 90% of the full-transmittance change. c Optical Density (ΔOD) = log[T bleached /T colored ], d Q d is ejected charge, determined from the in situ experiments. e Coloration efficiency (CE) =ΔOD/Q d . (b) Figure 5. Spectroelectrochemistry of 5d thin film on the ITO-coated glass substrate in 0.1 M Bu 4 NClO 4 / DMF under negative potential scanning. 5’f Polyimide Films (a) Property c omparison