4-(Trifluoromethoxy)phenyl-Containing Polymers as Promising Anodic Materials for Electrochromic Devices
1
Department of Chemical and Materials Engineering, National Yunlin University of Science and Technology, Yunlin 64002, Taiwan
2
Bachelor Program in Interdisciplinary Studies, National Yunlin University of Science and Technology, Yunlin 64002, Taiwan
3
Institute of Environmental Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan
*
Author to whom correspondence should be addressed.
Coatings 2020, 10(12), 1251; https://doi.org/10.3390/coatings10121251
Submission received: 26 November 2020
/
Revised: 9 December 2020
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Accepted: 16 December 2020
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Published: 18 December 2020
(This article belongs to the Special Issue Organic Synthesis and Characteristics of Thin Films)
Abstract
:Three 4-(trifluoromethoxy)phenyl-based polydithienylpyrroles (PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP)) were synthesized electrochemically and their electrochromic behaviors were characterized. The introduction of electron withdrawing trifluoromethoxy unit in the side chain of polydithienylpyrroles (PSNS) decreases the HOMO and LUMO energy levels of PSNS. PTTPP film displays three various colors (grayish-yellow at 0 V, grayish-blue at 1.0 V, and bluish-violet at 1.4 V) from reduced to oxidized states. The optical contrast of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) electrodes are 24.5% at 1050 nm, 49.0% at 916 nm, and 53.8% at 1302 nm, respectively. The highest η of the PTTPP electrode is 379.64 cm2 C−1 at 1050 nm. Three ECDs based on PTTPP, P(TTPP-co-DTC), or P(TTPP-co-DTP) as anodic film and PProDOT-Et2 as cathodic film were fabricated. PTTPP/PProDOT-Et2 ECD showed high transmittance change (35.7% at 588 nm) and high η (890.96 cm2·C−1 at 588 nm). P(TTPP-co-DTC)/PProDOT-Et2 and P(TTPP-co-DTP)/PProDOT-Et2 ECDs showed high transmittance change, rapid response time, adequate open circuit memory, and good electrochemical redox stability. Based on these findings, this work provides novel insights for appropriate design of high transmittance change and high efficient multi-colored electrochromic polymers.
1. Introduction
Electrochromic materials tune their colors reversibly upon applying various potentials or undergoing a redox process. To date, organic and inorganic electrochromic materials have received much interest owing to their probable utilizations in auto-dimming mirror, smart windows of architectures, energy storage devices, etc. [1,2,3]. Compared to inorganic electrochromic materials, organic electrochromic materials have the benefits of ease of electrochemical and chemical synthesis, large coloration efficiency, rapid electrochromic switching, low onset oxidation voltage, and satisfactory long-term cycling stability [4,5].
In general, conjugated polymers and bipyridinium salts (viologens) are familiar organic electrochromic materials. Polythiophene, polypyrrole, polycarbazole, polyaniline, polyindole, and PEDOT are the most commonly used polymeric materials in electrochemical devices [6,7,8,9,10,11]. According to these conjugated polymers, PProDOT-Et2, a derivative of PEDOT, shows prominent performances as a cathodic polymer in ECDs [12]. Polypyrrole and polycarbazole were reported as anodic polymers in ECDs owing to their good hole transporting stability, attractive optical performances, and excellent electroactive characters. Polythiophenes are widely used as electrochromic electrodes due to their good reversible redox behaviors, large conductivity, and large color contrast between reduced and oxidized states [13]. However, the oxidized potentials of non-modified polythiophenes are 1.5 V (vs. Ag/AgCl) [14]. PSNS consists of two thiophene rings and a pyrrole ring; the strong electron-donating pyrrole unit decreases the oxidized potentials of polymers to 0.7 V vs. Ag/AgCl [15].
Moreover, a trifluoromethoxy (CF3O-) substituent is an electron-withdrawing group, the incorporation of a trifluoromethoxy substituent on the side chain of PSNS decreases the LUMO/HOMO energy levels of PSNS slightly. The electrochromic properties will vary with the change of LUMO/HOMO energy levels.
This paper reports the electrosynthesis and electrochromic properties of three polydithienylpyrrole derivatives (PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP)). For a 3,6-di(2-thienyl)carbazole unit, the incorporation of thiophene rings at 3,6-locations of carbazole unit leads to a red shift of the optical UV–Vis band and diminishes the band gap [16]. Dithieno[3,2-b:2′,3′-d]pyrrole (DTP) is an electron-donating group with a coplanar fused-heterocycle configuration, which assists to increase the polymer backbone planarity and narrow the band gap between conduction band and valence band [17]. The copolymerization of different monomers gives rise to desirable combinations of electrochromic behaviors presented in homopolymers. Therefore, we also synthesized DTC- and DTP-containing copolymers. In addition, dual-type polymer ECDs were prepared using PTTPP, P(TTPP-co-DTC), or P(TTPP-co-DTP) as the anodic material, PProDOT-Et2 as the cathodic material, and an ionic liquid-containing electrolyte as the separation layer. Optical and electrochemical characterizations of PTTPP film, P(TTPP-co-DTC) film, P(TTPP-co-DTP) film, PTTPP/PProDOT-Et2 ECD, P(TTPP-co-DTC)/PProDOT-Et2 ECD, and P(TTPP-co-DTP)/PProDOT-Et2 ECD were explored systematically using UV–Vis spectra and electrochromic switching techniques. The cycling stability between the oxidized and reduced states is a crucial factor for ECDs [18,19]. Optical memory responds to the energy depletion during the long-term manipulations of ECDs [20,21]. Accordingly, the dual-type polymer ECDs were further explored for optical memory and electrochemical cycling stability.
2. Experimental
2.1. Materials
Starting chemicals and solvents in this study were bought from TCI, Aldrich, Alfa Aesar, and employed as received. DTC, ProDOT-Et2, and [EPI+][TFSI−] were synthesized on the basis of previously published methods [22,23,24]. The scheme of 4-(trifluoromethoxy)phenyl-containing SNS derivative (TTPP) is shown in Figure 1. PTTPP, P(TTPP-co-DTC), P(TTPP-co-DTP), and PProDOT-Et2 electrodes were polymerized potentiostatically at 0.9 V on glass substrates.
2.2. Preparation of 2,5-Di(Thiophen-2-yl)-1-(4-(Trifluoromethoxy)Phenyl)Pyrrole (TTPP)
A mixture of 4-(trifluoromethoxy)aniline (0.744 g, 4.2 mmol), 1,4-di(2′-thienyl)-1,4-butadione (0.35 g, 1.4 mmol), 12 mL toluene, and 7 mg p-toluenesulfonic acid was stirred for 36 h under reflux. Subsequently, toluene was removed, and the unrefined product was refined using column chromatography. Yield: 63%. 1H-NMR(700MHz, DMSO-d6): δ 7.51 (d, 4H, phenyl-H and Th-H), 7.34 (d, 2H, phenyl-H), 6.91 (d, 2H, Th-H), 6.72 (dd, 2H, Th-H), 6.59 (d, 2H, Py-H). Elem. Anal. Calcd. for C19H12F3NOS2: C, 58.30%; H, 3.09%; N, 3.58%. Found: C, 58.35%; H, 3.06%; N, 3.45%.
2.3. Electrochemical and Electrochromic Characterizations
The electrochemical properties of as-prepared PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) electrodes deposited on glass substrates were characterized using an electrochemical analyzer (CHI6081E, CH Instruments, Austin, TX, USA). Electrochromic properties of PTTPP film, P(TTPP-co-DTC) film, P(TTPP-co-DTP) electrode, PTTPP/PProDOT-Et2 ECD, P(TTPP-co-DTC)/PProDOT-Et2 ECD, and P(TTPP-co-DTP)/PProDOT-Et2 ECD were characterized by a spectrophotometer (V-670 JASCO Pfungstadt, Germany).
2.4. Fabrication of ECDs
The preparations of [EPI+][TFSI–])/PVdF-HFP composite electrolytes were represented previously [25]. The anodic layers (PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP)) were prepared potentiostatically onto glass substrates at +0.9 V, respectively, whereas the cathodic layer (PProDOT-Et2) was deposited potentiostatically onto glass substrate at +1.4 V. The electrodes were isolated by the composite electrolyte. The electrode area of as-prepared ECDs was 1.8 cm2.
3. Results and Discussion
3.1. Electrochemical Preparation of Electrodes
Figure 2 displays the synthetic schemes of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) and Figure 3 shows the potentiodynamic measurements of neat TTPP, DTC, and DTP and their mixtures (TTPP+DTC and TTPP+DTP) in a solution. As the potentiodynamic measurements scanned continued, the anodic and cathodic peaks in Figure 3 increased stage by stage, implying PTTPP, PDTC, PDTP, P(TTPP-co-DTC), and P(TTPP-co-DTP) films were electrodeposited onto the ITO substrates. The onset oxidized potentials (Eonset) of TTPP, DTC, and DTP were 0.68, 0.82, and 0.80 V, respectively. The Eonset disparities of TTPP vs. DTC and TTPP vs. DTP were smaller than 0.15 V, inferring the copolymerization of TTPP vs. DTC and TTPP vs. DTP was workable [26]. Furthermore, the Eonset of TTPP was smaller than those of DTP and DTC, implying that a 4-(trifluoromethoxy)phenyl-based dithienylpyrrole was more susceptible to oxidation than either the DTP or DTC. The oxidized peaks of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP), as shown in Figure 3, locate at 0.77, 1.55, and 0.96 V, respectively, whereas the reduced peaks of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) situate at 0.17, 0.15, and 0.34 V, respectively.
Figure 4a–c displays the cyclic voltammograms of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) electrodes, respectively, at scan rates between 25 and 200 mV s−1, while Figure 4d–f displays their corresponding charts of peak current and sweep velocity. The peak current densities raise linearly with raising scan rate, inferring PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) are well clung onto ITO surface and the redox reactions are non-diffusion limited processes [27].
3.2. Electrochromic Characterizations of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP)
As shown in Figure 5, the UV–Vis band of PTTPP film in the reduction state situated at 364 nm. The absorption band of P(TTPP-co-DTC) and P(TTPP-co-DTP) in the reduction state shifted bathochromically relative to PTTPP film. It is worth noting that the absorption band red shift value of P(TTPP-co-DTP) film is larger than that of P(TTPP-co-DTC) film, which can be ascribed to the fused-heterocycle of DTP unit being able to increase the planarity of repeating units in P(TTPP-co-DTP) backbones and diminish polymeric bandgap. As the application of potential increases gradually, the π–π* transition absorbance peak of PTTPP film begins to diminish, and bipolaron and polaron bands generate at ca. 532 and 1050 nm. Under similar condition, the bipolaron and polaron bands generate at 916 nm for P(TTPP-co-DTC) film and 1302 nm for P(TTPP-co-DTP) film. Table 1 displays the electrochromic photoimages of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) in a solution at different redox potentials; the anodic polymer films display reversible electrochromic phenomena in their neutral and oxidized states. The PTTPP film was grayish-yellow at 0 V, grayish-blue at 1.0 V, and bluish-violet at 1.4 V. Under similar circumstances, P(TTPP-co-DTC) displays obvious color transition with three colors (grayish-green at 0 V, grayish-blue at 1.0 V, and bluish-purple at 1.2 V), while P(TTPP-co-DTP) film shows three kinds of colors from reduced to oxidized states (gray at 0 V, grayish-blue at 0.6 V, and blue at 1.2 V). The colorimetric values of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) estimated at different voltages are summarized in Table 1, and the chromaticity diagrams of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) in reduced and oxidized state are displayed in Figure 6.
The band gap (Eg) of PTTPP film can be determined from the λonset of UV spectra by Planck equation (Eg = 1241/λonset) [28], and it is 2.34 eV (Table 2). The HOMO/LUMO energy levels of PTTPP film were determined using the following equations [29]:
where Eonset is corrected using ferrocene as internal standard. The EHOMO and ELUMO of PTTPP film are −4.91 and −2.52 eV, respectively.
EHOMO = −e(Eonset + 4.8) (vs. vacuum)
ELUMO = EHOMO + Eg
Double step chronoamperometry technique was used to estimate switching performances of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) [30]. Figure 7 exhibits the time-transmittance profiles of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) with an interval of 5 s between redox states. The coloration/bleaching time (τc and τb) of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) are summarized in Table 3. The τc and τb are estimated at 90% of whole transmittance variation (T90%). The τc and τb of three polymer films at visible light and near infrared light regions were found to be 1.85–2.49 s in [EPI+][TFSI−] solution.
The optical contrast ΔT (%) is a crucial parameter for electrochromic materials and devices [31]. The ΔTmax of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) are 24.5% at 1050 nm, 49.0% at 916 nm, and 53.8% at 1302 nm, respectively, in [EPI+][TFSI–] solution, indicating copolymers show higher ΔT than that of PTTPP homopolymer and the introduction of DTP group in the polymeric backbone leads to higher ΔTmax than that of DTC unit. For the three polymer films, P(TTPP-co-DTP) shows the highest ΔTmax (53.8%) at 1302 nm. As listed in Table 2, the ΔTmax of P(TTPP-co-DTP) film was larger than those reported for poly(1-co-EDOT) (ΔTmax = 32.9% at 500 nm) [32], PBCB (ΔTmax = 44% at 1000 nm) [33], and PBCP (ΔTmax = 39% at 1000 nm) [33].
The coloration efficiency (η) can be estimated by the following equations [36]:
where ΔOD, Tb, and Tc denote the variation of the optical density, the transmittance of bleaching state, and the transmittance of coloring state, respectively. The ηmax of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) films are 379.64 cm2/C at 1050 nm, 171.29 cm2/C at 916 nm, and 394.82 cm2/C at 1302 nm, respectively. P(TTPP-co-DTP) film shows the highest ηmax. PTTPP film shows higher η than those reported for poly(1-co-EDOT) (η = 173 cm2/C at 500 nm) [32], PBCB (η = 268.43 cm2/C at 1000 nm) [33], and PBCP (η = 236.18 cm2/C at 1000 nm) [33].
ΔOD = log(Tb/Tc)
η = ΔOD/Qd
3.3. Spectroelectrochemical Characterization of Electrochromic Devices
Dual-type complementary ECDs consisted of an anodic layer (PTTPP, P(TTPP-co-DTC), or P(TTPP-co-DTP)), a cathodic layer (PProDOT-Et2), and an ionic liquid/PVdF-HFP electrolyte were constructed and their optical performances were measured. As presented in Figure 8a, PTTPP/PProDOT-Et2 ECD displayed an absorption peak at ca. 367 nm at −0.4 V, which could be ascribed to the π–π* transition of PTTPP in the reduced state. Under the situation, the cathodic layer was light blue in its oxidized state, and PTTPP/PProDOT-Et2 ECD was gray at −0.4 V. However, the π–π* transition peak of PTTPP decreased gradually and a peak emerged at 588 nm progressively with increasing voltage. The PTTPP/PProDOT-Et2 ECD was deep blue at 1.2 V (Table 4). Under similar circumstances, P(TTPP-co-DTC)/PProDOT-Et2 and P(TTPP-co-DTP)/PProDOT-Et2 ECDs were dark blue at 1.2 and 1.4 V, respectively. The CIE chromaticity charts of PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs at bleached and colored voltages are displayed in Figure 9.
Figure 10a–c reveals the time-transmittance charts of PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs, respectively, and the ΔT, ΔOD, and coloration efficiency of PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs are listed in Table 2. The ΔTmax of PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs were 35.7% at 588 nm, 42.6% at 590 nm, and 48.1% at 592 nm, respectively. In other aspects, the ηmax of PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs were calculated to be 890.96 cm2/C at 588 nm, 512.79 cm2/C at 590 nm, and 519.27 cm2/C at 592 nm, respectively. The ΔTmax of PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs are larger than those of P(TTPA-co-EDOT)/PEDOT ECD (ΔTmax = 24% at 650 nm) [35] and P(FPTP-co-EDOT)/PEDOT ECD (ΔTmax = 23% at 555 nm) [36]. Moreover, PTTPP/PProDOT-Et2 ECD shows higher ηmax than that reported for P(TTPA-co-EDOT)/PEDOT ECD (ηmax = 545 cm2/C at 650 nm) [35].
The coloration/bleaching time of ECDs estimated after various cycles are shown in Table 3. The τc and τb of PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs are in the range of 0.87–0.99 s. The coloration/bleaching times of PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs were faster than those of PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) electrodes, indicating the ECDs changed color from bleached to colored state more quickly than PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) films in a solution.
3.4. Cycling Stability and Optical Memory of Electrochromic Devices
The cycling stability of PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs were monitored by cyclic voltammetry measurements at voltages between −1.0 and +1.8 V. As displayed in Figure 11, 95.2%, 97.2%, and 92.7%, respectively, of electroactivity were preserved for PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs after the 500th cycle, and 88.9%, 96.1%, and 91.3%, respectively, of electroactivity were preserved after the 1000th cycle, indicating PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs displayed a sufficient redox cycling stability.
The optical memory of PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs were measured at 588–592 nm by applying voltages at coloring state (+1.0 or +1.4 V) and bleaching state (−0.4 or −0.2 V) for 1 s for each 200 s time interval. As displayed in Figure 12, PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs presented sufficient open circuit memory at coloring state (the variation of transmittance was less than 5%) and bleaching state (transmittance change was less than 1.5%), verifying PTTPP/PProDOT-Et2, P(TTPP-co-DTC)/PProDOT-Et2, and P(TTPP-co-DTP)/PProDOT-Et2 ECDs showed adequate optical memory at coloring and bleaching states.
4. Conclusions
TTPP was synthesized and its corresponding homopolymers (PTTPP) and copolymers (P(TTPP-co-DTC) and P(TTPP-co-DTP)) were prepared. The anodic polymer films display reversible electrochromic phenomena in their neutral and oxidized states. The PTTPP film was grayish-yellow at 0 V, grayish-blue at 1.0 V, and bluish-violet at 1.4 V, whereas P(TTPP-co-DTP) film showed color changes from reduced to oxidized states (gray at 0 V, grayish-blue at 0.6 V, and blue at 1.2 V). Colorless-to-colorful switching investigations of anodic films show that P(TTPP-co-DTP) film has high ΔTmax (53.8% at 1302 nm) and PTTPP film has high η (379.64 cm2/C at 1050 nm). P(TTPP-co-DTP)/PProDOT-Et2 ECD exhibits high ΔTmax (48.1% at 592 nm) and a sufficient cycling stability, whereas PTTPP/PProDOT-Et2 ECD displays high η (890.96 cm2/C at 588 nm) and adequate optical memory at coloring and bleaching states, implying PTTPP, P(TTPP-co-DTC), and P(TTPP-co-DTP) films are promising candidates as anodic electrochromic materials for potential applications in motorcycle helmet-visors, electrochromic goggles, electrochromic display devices, and auto-dimming car mirror.
Author Contributions
Conceptualization, W.-H.W. and T.-Y.W.; methodology, W.-H.W.; formal analysis, W.-H.W. and T.-Y.W.; investigation, W.-H.W., J.-C.C. and P.-Y.L.; resources, Y.-C.L.; data curation, W.-H.W. and T.-Y.W.; writing—original draft preparation, T.-Y.W.; writing—review and editing, T.-Y.W.; project administration, T.-Y.W. and Y.-C.L.; funding acquisition, T.-Y.W. and Y.-C.L. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by Ministry of Science and Technology of Republic of China, Grant No. 108-2221-E-224-049-MY3.
Conflicts of Interest
The authors declare no conflict of interest.
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Figure 1.
The synthetic scheme of 4-(trifluoromethoxy)phenyl-containing SNS derivative.
Figure 2.
The electrosynthetic schemes of three 4-(trifluoromethoxy)phenyl-containing PSNS.
Figure 3.
Cyclic curves of: (a) 2 mM TTPP; (b) 2 mM DTC; (c) 2 mM DTP; (d) 2 mM TTPP + 2 mM DTC; and (e) 2 mM TTPP + 2 mM DTP in 0.1 M lithium perchlorate/acetonitrile. The red line indicates the first cycle.
Figure 3.
Cyclic curves of: (a) 2 mM TTPP; (b) 2 mM DTC; (c) 2 mM DTP; (d) 2 mM TTPP + 2 mM DTC; and (e) 2 mM TTPP + 2 mM DTP in 0.1 M lithium perchlorate/acetonitrile. The red line indicates the first cycle.
Figure 4.
CV plots of: (a) PTTPP; (b) P(TTPP-co-DTC); and (c) P(TTPP-co-DTP) electrodes at different scan rates in 0.1 M lithium perchlorate/acetonitrile. The relationship of i vs. v of: (d) PTTPP; (e) P(TTPP-co-DTC); and (f) P(TTPP-co-DTP) electrodes.
Figure 4.
CV plots of: (a) PTTPP; (b) P(TTPP-co-DTC); and (c) P(TTPP-co-DTP) electrodes at different scan rates in 0.1 M lithium perchlorate/acetonitrile. The relationship of i vs. v of: (d) PTTPP; (e) P(TTPP-co-DTC); and (f) P(TTPP-co-DTP) electrodes.
Figure 5.
Absorption spectra of: (a) PTTPP; (b) P(TTPP-co-DTC); and (c) P(TTPP-co-DTP) films at different voltages.
Figure 5.
Absorption spectra of: (a) PTTPP; (b) P(TTPP-co-DTC); and (c) P(TTPP-co-DTP) films at different voltages.
Figure 6.
CIE chromaticity charts of: (a) PTTPP; (b) P(TTPP-co-DTC); and (c) P(TTPP-co-DTP) electrodes in [EPI+][TFSI–] solution in the oxidized and reduced states.
Figure 6.
CIE chromaticity charts of: (a) PTTPP; (b) P(TTPP-co-DTC); and (c) P(TTPP-co-DTP) electrodes in [EPI+][TFSI–] solution in the oxidized and reduced states.
Figure 7.
Transmittance profiles of: (a) PTTPP film at 532 and 1050 nm; (b) P(TTPP-co-DTC) film at 398 and 916 nm; and (c) P(TTPP-co-DTP) film at 484 and 1302 nm under potentials between 0 and +1.0 V. Time interval: 5 s.
Figure 7.
Transmittance profiles of: (a) PTTPP film at 532 and 1050 nm; (b) P(TTPP-co-DTC) film at 398 and 916 nm; and (c) P(TTPP-co-DTP) film at 484 and 1302 nm under potentials between 0 and +1.0 V. Time interval: 5 s.
Figure 8.
UV plots of: (a) PTTPP/PProDOT-Et2; (b) P(TTPP-co-DTC)/PProDOT-Et2; and (c) P(TTPP-co-DTP)/PProDOT-Et2 ECDs at various voltages.
Figure 8.
UV plots of: (a) PTTPP/PProDOT-Et2; (b) P(TTPP-co-DTC)/PProDOT-Et2; and (c) P(TTPP-co-DTP)/PProDOT-Et2 ECDs at various voltages.
Figure 9.
CIE chromaticity charts of: (a) PTTPP/PProDOT-Et2; (b) P(TTPP-co-DTC)/PProDOT-Et2; and (c) P(TTPP-co-DTP)/PProDOT-Et2 ECDs at bleached and colored states.
Figure 9.
CIE chromaticity charts of: (a) PTTPP/PProDOT-Et2; (b) P(TTPP-co-DTC)/PProDOT-Et2; and (c) P(TTPP-co-DTP)/PProDOT-Et2 ECDs at bleached and colored states.
Figure 10.
Transmittance of: (a) PTTPP/PProDOT-Et2 ECD at 588 nm (between −0.2 and +1.0 V); (b) P(TTPP-co-DTC)/PProDOT-Et2 ECD at 590 nm (between −0.4 and 1.4 V); and (c) P(TTPP-co-DTP)/PProDOT-Et2 ECD at 592 nm (between −0.4 and 1.4 V).
Figure 10.
Transmittance of: (a) PTTPP/PProDOT-Et2 ECD at 588 nm (between −0.2 and +1.0 V); (b) P(TTPP-co-DTC)/PProDOT-Et2 ECD at 590 nm (between −0.4 and 1.4 V); and (c) P(TTPP-co-DTP)/PProDOT-Et2 ECD at 592 nm (between −0.4 and 1.4 V).
Figure 11.
CV plots of: (a) PTTPP/PProDOT-Et2; (b) P(TTPP-co-DTC)/PProDOT-Et2; and (c) P(TTPP-co-DTP)/PProDOT-Et2 ECDs.
Figure 11.
CV plots of: (a) PTTPP/PProDOT-Et2; (b) P(TTPP-co-DTC)/PProDOT-Et2; and (c) P(TTPP-co-DTP)/PProDOT-Et2 ECDs.
Figure 12.
Optical memory effect of: (a) PTTPP/PProDOT-Et2 ECD measured at 588 nm; (b) P(TTPP-co-DTC)/PProDOT-Et2 ECD measured at 590 nm; and (c) P(TTPP-co-DTP)/PProDOT-Et2 ECD measured at 592 nm.
Figure 12.
Optical memory effect of: (a) PTTPP/PProDOT-Et2 ECD measured at 588 nm; (b) P(TTPP-co-DTC)/PProDOT-Et2 ECD measured at 590 nm; and (c) P(TTPP-co-DTP)/PProDOT-Et2 ECD measured at 592 nm.
Table 1.
Electrochromic behaviors of PSNS.
| Polymers | E/V | Photographs | L* | a* | b* |
|---|---|---|---|---|---|
| PTTPP | 0 |  | 92.11 | −2.13 | 19.48 |
| 1.0 |  | 91.09 | −2.13 | 17.43 | |
| 1.4 |  | 75.4 | 6.8 | 4.77 | |
| P(TTPP-co-DTC) | 0 |  | 86.23 | −3.16 | 43.75 |
| 1.0 |  | 71.81 | −3.3 | 9.7 | |
| 1.2 |  | 68.18 | −0.87 | 7.17 | |
| P(TTPP-co-DTP) | 0 |  | 82.49 | 14.04 | 14.73 |
| 0.6 |  | 87.79 | −4.73 | 3.79 | |
| 1.2 |  | 84.85 | −3.03 | −1.81 |
L* indicates the lightness, a* and b* represent the color channels.
Table 2.
Comparisons of the ΔTmax and ηmax for polymers and ECDs.
| Polymers and ECDs | λ/nm | Eg/eV | ΔTmax/% | ΔODmax/% | ηmax/cm2 C−1 |
|---|---|---|---|---|---|
| PTTPP | 1050 | 2.34 | 24.5 | 16.5 | 379.64 |
| P(TTPP-co-DTC) | 916 | - | 49.0 | 41.9 | 171.29 |
| P(TTPP-co-DTP) | 1302 | - | 53.8 | 39.5 | 394.82 |
| poly(1-co-EDOT) [32] | 500 | - | 32.9 | - | 173 |
| PBCB [33] | 1000 | 1.77 | 44 | - | 268.43 |
| PBCP [33] | 1000 | 1.74 | 39 | - | 236.18 |
| PTTPP/PProDOT-Et2 ECD | 588 | - | 35.7 | 59.4 | 890.96 |
| P(TTPP-co-DTC)/PProDOT-Et2 ECD | 590 | - | 42.6 | 56.9 | 512.79 |
| P(TTPP-co-DTP)/PProDOT-Et2 ECD | 592 | - | 48.1 | 77.8 | 519.27 |
| P(TTPA-co-EDOT)/PEDOT ECD [34] | 650 | - | 24 | - | 545 |
| P(FPTP-co-EDOT)/PEDOT ECD [35] | 555 | - | 23 | - | - |
Table 3.
Coloring-bleaching kinetics of polymer electrodes and ECDs.
| Polymers and ECDs | λmax/nm | Cycle No. | T | τ (T90%) | Stability (100 cycles) | ||||
|---|---|---|---|---|---|---|---|---|---|
| Tb/% | Tc/% | ΔT/% | τc/s | τb/s | |||||
| PTTPP in [EPI+][TFSI–] | 532 | 1 | 51.9 | 41.7 | 10.2 | 2.32 | 1.99 | - | |
| - | - | 50 | 49.6 | 40.7 | 8.9 | 2.33 | 1.86 | - | |
| - | - | 100 | 48.7 | 40.4 | 8.3 | 2.29 | 2.07 | 81.4% | |
| - | 1050 | 1 | 77.7 | 53.2 | 24.5 | 2.41 | 1.87 | - | |
| - | - | 50 | 76.4 | 51.9 | 24.5 | 2.41 | 1.89 | - | |
| - | - | 100 | 75.3 | 52.4 | 22.9 | 2.39 | 1.95 | 93.5% | |
| P(TTPP-co-DTC) in | 398 | 1 | 26.0 | 11.5 | 14.5 | 2.34 | 2.18 | - | |
| [EPI+][TFSI–] | - | 50 | 25.6 | 11.4 | 14.2 | 2.41 | 2.28 | - | |
| - | - | 100 | 25.4 | 11.4 | 14.0 | 2.30 | 2.33 | 96.6% | |
| - | 916 | 1 | 79.2 | 30.2 | 49.0 | 2.03 | 2.42 | - | |
| - | - | 50 | 78.7 | 33.1 | 45.6 | 1.94 | 2.46 | - | |
| - | - | 100 | 78.6 | 35.4 | 43.2 | 1.96 | 2.49 | 88.2% | |
| P(TTPP-co-DTP) in | 484 | 1 | 64.3 | 24.7 | 39.6 | 1.85 | 1.88 | - | |
| [EPI+][TFSI–] | - | 50 | 64.0 | 24.5 | 39.5 | 1.87 | 1.86 | - | |
| - | - | 100 | 63.9 | 24.4 | 39.5 | 1.97 | 1.91 | 99.7% | |
| - | 1302 | 1 | 90.1 | 36.3 | 53.8 | 1.96 | 1.92 | - | |
| - | - | 50 | 88.9 | 35.5 | 53.4 | 1.94 | 2.02 | - | |
| - | - | 100 | 88.7 | 35.4 | 53.3 | 1.92 | 1.89 | 99.1% | |
| PTTPP/ PProDOT-Et2 ECD | 588 | 1 | 47.9 | 12.2 | 35.7 | 0.96 | 0.97 | - | |
| - | 50 | 47.8 | 12.8 | 35.0 | 0.94 | 0.94 | - | ||
| - | 100 | 48.0 | 13.9 | 34.1 | 0.99 | 0.92 | 95.5% | ||
| P(TTPP-co-DTC)/ | 590 | 1 | 58.3 | 15.7 | 42.6 | 0.99 | 0.94 | - | |
| PProDOT-Et2 ECD | - | 50 | 58.0 | 15.6 | 42.4 | 0.93 | 0.91 | - | |
| - | - | 100 | 56.8 | 15.7 | 41.1 | 0.97 | 0.90 | 96.5% | |
| P(TTPP-co-DTP)/ | 592 | 1 | 57.7 | 9.6 | 48.1 | 0.94 | 0.88 | - | |
| PProDOT-Et2 ECD | - | 50 | 56.9 | 9.7 | 47.2 | 0.92 | 0.90 | - | |
| - | - | 100 | 56.7 | 10.1 | 46.6 | 0.87 | 0.94 | 96.9% | |
Table 4.
Photoimages and L*, a*, and b* values of ECDs.
| ECDs | E/V | Photoimages | L* | a* | b* |
|---|---|---|---|---|---|
| PTTPP/PProDOT-Et2 | −0.4 |  | 87.38 | −1.64 | 8.91 |
| 0 |  | 85.98 | −2.28 | 5.47 | |
| 0.6 |  | 72.62 | 4.5 | −10.44 | |
| 0.8 |  | 65.31 | 4.11 | −19.6 | |
| 1.2 |  | 56.03 | 5.65 | −30.98 | |
| P(TTPP-co-DTC)/PProDOT-Et2 | 0 |  | 81.05 | −7.69 | 19.29 |
| 0.4 |  | 73.43 | −3.39 | 6.91 | |
| 0.6 |  | 67.22 | −1.06 | −2.54 | |
| 0.8 |  | 61.72 | −0.31 | −10.81 | |
| 1.2 |  | 59 | 1.65 | −15.34 | |
| P(TTPP-co-DTP)/PProDOT-Et2 | −0.4 |  | 81.78 | 8.71 | 5.4 |
| 0 |  | 85.15 | −1.07 | 4.43 | |
| 0.6 |  | 76.9 | 1.94 | −10.44 | |
| 0.8 |  | 70.37 | 3.26 | −19.12 | |
| 1.4 |  | 57.72 | 5.9 | −35.2 |
L* indicates the lightness, a* and b* represent the color channels.
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Wang, W.-H.; Chang, J.-C.; Lee, P.-Y.; Lin, Y.-C.; Wu, T.-Y. 4-(Trifluoromethoxy)phenyl-Containing Polymers as Promising Anodic Materials for Electrochromic Devices. Coatings 2020, 10, 1251. https://doi.org/10.3390/coatings10121251
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Wang W-H, Chang J-C, Lee P-Y, Lin Y-C, Wu T-Y. 4-(Trifluoromethoxy)phenyl-Containing Polymers as Promising Anodic Materials for Electrochromic Devices. Coatings. 2020; 10(12):1251. https://doi.org/10.3390/coatings10121251
Chicago/Turabian StyleWang, Wen-Hsin, Jui-Cheng Chang, Pei-Ying Lee, Yuan-Chung Lin, and Tzi-Yi Wu. 2020. "4-(Trifluoromethoxy)phenyl-Containing Polymers as Promising Anodic Materials for Electrochromic Devices" Coatings 10, no. 12: 1251. https://doi.org/10.3390/coatings10121251
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