【作者】 杜青；

【导师】 徐春叶；

【作者基本信息】 中国科学技术大学 ， 高分子化学与物理， 2014， 博士

【摘要】 电致变色(Electrochromism, EC)是指材料在外加驱动电压施加下发生了氧化还原反应过程,或者分子结构内有电荷(如电子或离子)发生注入或抽出,物质的光学属性如透过率、吸收率和发射率三者在可见光、红外光谱区域内产生了可逆变换,这个变换的宏观表现是材料的色彩以及透明度发生的可逆性地转变。目前EC的研究重点在于如何提高其变色性能,而性能的提高核心在于新材料的开发。其中,作为电致变色材料的重要组成部分,供体-受体型(Donor-acceptor)共轭聚合物电致变色材料是由供体单元(给电子基团)和受体单元(吸电子基团)所构成,能够通过分子结构的设计来解决材料的变色颜色、光学对比度(△T%)。以及响应时间等问题。此外,这类材料还具有来源广泛、价格低廉、驱动电压低、颜色响应速度快以及工作寿命长等优点而逐渐受到重视,并广泛应用于各种类型的电致变色器件中。本文主要围绕供体-受体型聚合物作为电致变色材料,通过改变供体和受体基团和材料的主链结构及侧基基团,研究了材料的合成、表征及性能。通过对电致变色性能的测试,选用电荷相互匹配的对电极组装成为聚合物电致变色器件(PECDs),进而对器件的性能进行表征和优化,以期望得到具备多种颜色显示、光学对比度高、变色响应速度快、工作寿命长的电致变色器件。这篇论文有如下四个部分：第一部分：合成单体8,11-二-(4-噻吩-2-基)苊[1,2-b]喹喔啉(DTAQ)经由电化学聚合得到供体-受体型聚合物薄膜(PDTAQ),采用化学表征手段证明其结构。光谱电化学及电致变色性能显示聚合物薄膜具有明显的颜色变换,光学对比度接近50%,而且变色响应速度快。PDTAQ薄膜作为工作电极,对电极分别为普鲁士蓝(PB)和五氧化二钒(V205)薄膜,电解液LiC104/PC组装成不同的三明治的互补型的电致变色器件并进行性能研究,结果表明：PDTAQ/PB器件和PDTAQ/V2O5器件在光学吸收性能、颜色变化、光学对比度(AT%)和响应时间方面都因对电极的不同而表现出较大的电致变色性能差异。因此,通过设计D-A型电致变色材料并利用不同类型的电荷相互匹配的对电极组装成电致变色器件的设计方案为多颜色显示器件提供了一种新的设计思路。第二部分：本章利用两种供体单元通过偶联聚合成功合成了聚4-二苯胺苯甲醛-4,8-二乙基己基氧苯[1,2-b；3,4-b]二噻吩(PBDTTPA-CHO),并对其官能团进行修饰合成了PBDTTPA-COOH,得到两种侧基上具有不同吸电子基团的D-π-A型的共轭聚合物。PBDTTPAs都具备优异的热稳定性能,确保了材料在长期工作中的稳定性。此外,聚合物在薄膜和器件状态时在不同电压下的可见光和红外波段均有良好的电致变色性能。因此,通过对D-A型共轭聚合物进行分子结构中吸电子基团的调整可以调节其丰富的颜色变化、对比度及变色速度,进而实现显示器件的多样性。第三部分：基于本实验室研究的ProDOT作为电致变色基团,利用吸电子基团(1,3,5-三嗪)和给电子基团(三苯胺)分别作为中心核,通过分子设计来合成星型电致变色材料。合成单体M1和M2并利用电化学聚合得到其聚合物(P1、P2)。P1和P2的中心核分别是吸电子基团和供电子基团的差异表现在包括颜色、驱动电压、光学对比度和响应时间在内的不同的电致变色性能。P1由在中性态下的粉红色变成氧化态(1.5V)的浅灰色,P2展现出可逆的电致变色性能并呈现多颜色的显示：在还原状态下为黄绿色,半氧化态为蓝绿色,全氧化态为蓝色。因此,通过分子结构形状的设计拓宽了供体-受体型聚合物电子变色材料的研究领域。第四部分：主链结构中的电子供体单元：一维结构的苯并二噻吩(BDT),同时引入两种受体单元：4,7-二噻吩-1,2,3-苯并二噻唑(DTBT)以及噻吩吡咯烷酮(TPD),调节供受体基团上侧基上烷基链的长度,通过Stille偶联聚合反应成功得到了新型的A1-D-A2的聚合物材料。侧基的长度对PBDT系列的热分解温度区别不大,并且具有较好的热稳定性；对系列PTBD材料溶液状态和固体膜进行紫外可见吸收光谱的测试发现：受体单元TPD和供体单元BDT的侧基上取代基的长度对最大吸收波长有明显的影响。A1-D-A2型的聚合物有利于降低材料的能带隙,PTBD聚合物在溶液状态和薄膜状态下的光学能带隙都低于1.75eV,这说明进而可以调节材料在光学范围内对颜色的调节和性能的控制。对系列聚合物进行了电化学测试发现吸电子基团上的给电子能力的强弱对材料的氧化电位有极大的影响。另外,对于主链结构上供电子基团BDT的侧基上烷基链的长度影响着材料的氧化电位,如烷基链长度越长,给电子能力增强,材料容易变成氧化状态,所需的电位较低。因此,采用侧基取代基团的设计进而调节材料的光学及电学性能为新的聚合物电致变色材料的研究拓宽了方向。更多还原

【Abstract】 Electrochromic (EC) is defined that a material takes place reversible redox reaction or electrical charges (electrons or ions) injected or ejected and its optical properties (transmittance, absorption and reflectivity) exhibit reversible changes in visible light region. The macro performance for molecules display that the reversible changes of the color and transparency of these changes. Being modified by designing molecules structure, donor-acceptor type electrochromic polymers are paid attention for a wealth of sources, low cost, low driving voltage, good optical quality, fast color conversion and long working stability.In this article, we studied that the synthesis, characterization and properties of donor-acceptor type electrochromic polymers by modifying the donor units and acceptor units. We measured the properties of the electrochromic polymers and chose the counter electrodes which electrical charges matched with the polymer working electrodes. We characterized and optimized the electrochromic properties of devices, to obtain devices with multi-colours, high optical contrast, fast response switching times. The study work below were undergoing through four parts:In the first part,8,11-Di-(4-thiophen-2-yl)acenaphtho [1,2-b]quinoxaline (DTAQ) was successfully synthesized by Stille coupling reaction and the corresponding polymer was prepared electrochemically. Electrochromic properties of the polymer film reveal that PDTAQ film show distinct color states and high optical contrast accompany fast switching times. The complementary ECDs which are based on the PDTAQ film as working electrode, prussian blue (PB) and V2O5as counter electrode respectively. LiClO4/PC solution as electrolyte were assembled and characterizaed. The results illustrate that the properties of PDTAQ/PB device and PDTAQ/V2O5devices (including the absorption, color changes,△T%and response times) can be adjusted by the counter electrodes.In the second part, a novel donor-π-bridge-acceptor copolymer, PBDTTPA-CHO, containing4-(Bis(4-bromophenyl)-amino)benzaldehyde and4,8-bis-(2-ethyl-hexyloxy)-oxybenzo-[1,2-b:3,4-b’]dithiophene was successfully synthesized using Stille coupling polymerization and the pendant aldehyde group was modified with cyanoacetic acid to synthesize another polymer, PBDTTPA-COOH. Both of polymers are soluble in ordinary organic solvents so that they can be easily made films onto rigid or flexible substrates. The polymers with different electrophilic groups exhibit different electrochromic behaviors, including applied driving voltages, completely different colors and switching transmittances. We fabricated and studied the sandwiched ECDs using a PBDTTPA layer as the working electrode and vanadium pentoxide film acted as the counter electrode. Upon the contribution of counter electrodes, devices of both polymers show similar color changes but higher transmittance than their films.In the third part, star branched monomers2,4,6-tris(4-(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6-yl)-phenyl)-1,3,5-triazine (M1) and tris(4-(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]-dioxepin-6-yl)-phenyl)amine (M2) were designed and successfully synthesized via Stille coupling reaction and the corresponding polymers (PI, P2) were synthesized using electrochemical polymerization. Structures of both of the monomers were certified by NMR and FT-IR. p1and P2, having electron-withdrawing and electron-donating core respectively, display various electrochromic behaviors, including distinguished colors, applied driving voltages and switching transmittances. Therefore, this part provided a new method for electrochromic molecules design.In the fourth part, a series different side chains of donor-acceptor (A1-D-A2) conjugated copolymers with a donor unit (benzo[1,2-b:4,5-b’]dithiophene (BDT)) and two different electron-accepting untis (N-alkylthieno[3,4-c]pyrrole-4,6-dione (TPD) and dithiophenebenzothiadiazole (DTBT)) is designed and prepared. The series of polymers display two intense absorptions in the wavelength range of600-900nm, and the band gaps (Eg) are lower than1.70eV. The optical and electrochemical properties of these polymers show that the copolymers have the low band gaps and the HOMO and LUMO energy levels are different. The results indicate that different soluble alkyl chain can optimize the properties of the copolymers, which are potential in conjugated polymer electrochromic materials and devices.更多还原