ESR/UV-Vis-NIR spectroelectrochemical study and electrochromic contrast enhancement of a polythiophene derivative bearing a pendant viologen
ESR/UV-Vis-NIR spectroelectrochemical study and electrochromic contrast enhancement of a polythiophene derivative bearing a pendant viologen
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DOI：
10.1039/c5ra04618a
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发表时间：
2015-01-01
期刊：
影响因子：
3.9
通讯作者：
Kvarnstrom, Carita
中科院分区：
文献类型：
--
作者：
Gadgil, Bhushan;Damlin, Pia;Kvarnstrom, Carita
紫精在电致变色材料领域中的重要性是众所周知的，因为它们形成强烈颜色的自由基阳离子。在这项研究中，1-[6-[（4-甲基-3-噻吩基）氧基]己基]-4，4 '-联吡啶六氟磷酸盐（Th-V）被合成，并在含有水和乙腈（v/v; 50：50）的溶剂混合物中以0.1M高氯酸锂（LiClO 4）作为电解质盐进行电聚合，在电极表面上产生带有紫精的聚噻吩（PTh-V）膜。所得聚合物显示出氧化还原活性紫精和共轭聚噻吩部分的电化学活性。采用电子自旋共振（ESR）和紫外-可见-近红外（UV-Vis-NIR）光谱同时记录的多现场光谱电化学技术研究了聚合物的氧化还原行为。结果表明，在PTh-V薄膜的n-和p-掺杂过程中，仅产生极化子电荷载流子。聚合物薄膜显示出增强的电致变色对比度，由于引入了一个悬垂紫精基团到噻吩单元。该膜在深紫色（在0.6V下）和几乎透明（在1.0V下）之间可逆地切换，显示出良好的光学对比度，着色效率约为0.5%。在610 nm处为305 cm（2）C-1。切换透射率动力学证明了快速响应时间以获得漂白状态和优异的操作稳定性，其中在着色/漂白状态之间可重复电压切换1000个循环。发现聚噻吩主链增强了共轭PTh-V氧化还原聚合物的热稳定性。PTh-V具有优异的光学对比度、急剧的颜色变化和高的色效率以及足够的热行为，这表明PTh-V在电致变色器件（ECD）应用中的潜力。
The importance of viologens in the field of electrochromic materials is well recognized due to their intensely colored radical cation formation. In this study, 1-[6-[(4-methyl-3-thienyl) oxy] hexyl]-4,4'-bipyridium hexafluorophosphate (Th-V) was synthesized and electropolymerized in a solvent mixture comprising water and acetonitrile (v/v; 50 : 50) with 0.1 M lithium perchlorate (LiClO4) as an electrolyte salt, yielding a viologen bearing polythiophene (PTh-V) film on an electrode surface. The resulting polymer shows electrochemical activity from both the redox active viologen and the conjugated polythiophene moieties. The redox behavior of the polymer was studied by multi in situ spectroelectrochemical technique by means of simultaneous recording of electron spin resonance and UV-Vis-near infrared (ESR/UV-Vis-NIR) spectra. The results indicate that only polaron charge carriers are created during both n-and p-doping of the PTh-V film. The polymer film shows enhanced electrochromic contrast due to the introduction of a pendant viologen group into the thiophene unit. The film switched reversibly between dark violet (at 0.6 V) and almost transparent (at 1.0 V) showing good optical contrast with a coloration efficiency of ca. 305 cm(2) C-1 at 610 nm. The switching transmittance kinetics demonstrate fast response times to attain a bleached state and excellent operational stability with repeatable voltage switching between colored/bleached states for 1000 cycles. The polythiophene backbone was found to strengthen the thermal stability of the conjugated PTh-V redox polymer. The excellent optical contrast with sharp color changes and high color efficiency combined with adequate thermal behavior suggests the potential of PTh-V in the electrochromic device (ECD) application.