交联结构噻吩类电致变色聚合物的设计合成及性质研究

发布时间：2018-09-04 14:06

【摘要】：随着全球能源的急剧消耗和环境的不断恶化,节能环保材料吸引了人们的广泛关注。电致变色材料正是这样一种可以改变人类生活方式并且有助于合理利用能源的新型功能材料。导电聚合物因结构易修饰、着色效率较高、响应时间较短、光学对比度较高及较丰富的颜色变换而成为电致变色材料中最具有潜力的一类物质。导电聚合物电致变色机理是基于聚合物的氧化还原与离子的掺杂与脱掺杂两个过程,而这样两个过程与聚合物的结构有着非常密切的关系。本论文通过合理的分子结构设计得到具有不同分子构型的单体,通过电化学聚合构筑一系列具有不同交联结构的噻吩类电致变色聚合物,探究单体分子构型-聚合物交联结构-电致变色性质之间的关系。本论文第一部分通过引入不同个数的苯至噻吩-吡咯-噻吩结构中,形成了中间以苯为桥、外围具有四个噻吩单元的新型单体(PhSNS,BPhSNS,TPhSNS),经电化学形成了交联结构的聚合物。由于桥键单元苯环个数的变化即桥键空间位阻大小的变化,使得三种单体可能具有不同的分子构型,从而可能导致聚合物表现不同的交联结构。单体循环伏安曲线表明,相比TPhSNS和BPhSNS,PhSNS具有两个氧化还原峰,量子化学分析证实这可能主要是PhSNS和BPhSNS、TPhSNS具有不同的分子构型,PhSNS单体的两条噻吩-吡咯-噻吩结构中噻吩和吡咯的扭曲角不相同(21.2°,40.2°),而BPhSNS、TPhSNS两条噻吩-吡咯-噻吩都具有相同的扭曲角(22.4°),这使得前者和后两者具有不同的电化学和光学性质。由于三个单体具有相似的起始氧化还原电位及三个单体的聚合物薄膜具有相似的氧化还原曲线,使得其相应的聚合物薄膜具有相似的多色变色行为(黄色-灰绿色-灰色),聚合物薄膜pPhSNS、pBPhSNS在1100 nm处的对比度为40%左右,着色时间和褪色时间为1 s左右,但由于TPhSNS结构中三联苯强的刚性使得其具有差的溶解性,从而导致相应的聚合物薄膜pTPhSNS具有相对较差的电致变色性质。但是,TPhSNS通过与EDOT进行共聚,发现共聚物pTPhSNS-EDOT相比均聚物pTPhSNS薄膜电致变色性能具有很大的改善,表现出合理的光学对比度40%(1100 nm)、快速的响应速度0.37 s(1100 nm)及良好的电化学稳定性等,这可能是因为引入柔性结构的EDOT结构至pTPhSNS聚合物形成了想要的交联结构聚合物薄膜。本论文第二部分通过引入不同个数苯至噻吩-咔唑-噻吩结构单元中,同样形成了外围具有四个噻吩的新型结构单体(BTCPh,BTCBPh),多位点的单体经电化学聚合之后形成了交联结构聚合物薄膜,同样由于中心苯环个数及空间位阻的变化,导致单体具有不同的分子构型,导致形成不同的交联结构聚合物。单体循环伏安曲线、紫外光谱分析证明两个单体具有相似的电化学及光学性质,聚合物薄膜pBTCPh、pBTCBPh同样表现出相似的氧化还原曲线,这使得两种聚合物薄膜具有相似的光谱电化学性质,且有相似的变色行为。动力学结果表明,聚合物薄膜pBTCPh和pBTCBP表现出相似的光学对比度,在410 nm、660、1100nm的光学对比度分别为25%、40%、50%。从电致变色响应时间来看,pBTCPh薄膜相比pBTCBPh具有更快的响应速度,特别是在660 nm,前者的响应时间为后者的一半,从扫描电镜图谱来看,这可能是由于pBTCPh薄膜相比pBTCBPh具有更加疏松的颗粒堆积方式,有利于电致变色过程中离子的嵌入与脱出过程,从而导致前者比后者响应速度更快。此外,从电致变色过程中电荷注入行为来看,pBTCPh相比pBTCBPh具有更加快速的电荷注入能力,同样能够加快电致变色的响应。本论文第三部分以四苯基甲烷为中心结构单元,通过still偶联在四个苯单元接入不同数目的噻吩单元形成新的单体结构(TPhTTh、TPhTBTh、TPhBTThBBr),由于外围结构同样为四个噻吩单元,经电聚合也能够形成交联结构的聚合物。由于四苯基甲烷中心原子碳为sp_3杂化,单体经电化学聚合形成的聚合物共轭长度是可控的,因此本部分将还将研究不同共轭长度对电致变色性能的影响。三个单体的循环伏安曲线、量子化学计算分析及紫外光谱表明,随着外围噻吩数目的增加,单体的共轭水平也随着增加,同时其紫外光谱发生相应的红移,起始氧化电位更低。从三个单体的电化学聚合中发现,TPhTTh不能有效地成膜,TPhTBTh、TPhBTThBBr很好地沉积到ITO表明上,形成相应的聚合物薄膜pTPhTBTh、p TPhBTThBBr;聚合物薄膜的循环伏安及紫外光谱表明,pTPhBTThBBr具有更低的氧化电压,且红移40 nm,中性态为橙黄色。两种聚合物薄膜的电化学光谱表明,后者具有更加明显的光谱变化,同时后者具有更好的电致变色性质,高的光学对比度55%(1100 nm),快速的响应速度及良好的电化学稳定性。从两种薄膜的扫描电镜表明,后者薄膜显示出比较疏松的颗粒堆积形貌,这可能是导致后者电致变色性能好的重要原因。此外,pTPhBTThBBr薄膜相比pTPhTBTh具有更好的共轭水平,这可能也是导致后者性能好的原因。
[Abstract]:With the rapid consumption of global energy and the deterioration of the environment, energy-saving and environmental protection materials have attracted wide attention. Electrochromic materials are a new type of functional materials which can change the way of human life and contribute to the rational use of energy. Conductive polymers are easy to modify their structures, have high coloring efficiency and short response time. The electrochromic mechanism of conducting polymers is based on the two processes of redox and ion doping and de-doping, which are closely related to the structure of polymers. A series of thiophene electrochromic polymers with different cross-linking structures were synthesized by electrochemical polymerization. The relationship between molecular configuration, cross-linking structure and electrochromic properties of thiophene was investigated. In the first part of this paper, different number of benzene was introduced. In the thiophene-pyrrole-thiophene structure, a new monomer (PhSNS, BPhSNS, TPhSNS) with four thiophene units was formed, which was bridged by benzene and electrochemically formed a crosslinked polymer. Compared with TPhSNS and BPhSNS, PhSNS has two redox peaks. Quantum chemical analysis shows that this may be mainly due to the different molecular configurations of PhSNS and BPhSNS, TPhSNS, and the thiophene and pyrrole thiophene in the two thiophene-pyrrole-thiophene structures of PhSNS. Both BPhSNS and TPhSNS have the same twist angle (22.4 degrees), which makes the former and the latter have different electrochemical and optical properties. The original curve makes the corresponding polymer film have similar polychromic behavior (yellow-grey-green-grey). The contrast of the polymer film pPhSNS and pBPhSNS is about 40% at 1100 nm, and the coloring time and fading time are about 1 s. However, due to the rigidity of the terphenyl in the structure of TPhSNS, the polymer film has poor solubility. However, by copolymerizing with EDOT, it was found that the electrochromic properties of the copolymer pTPhSNS-EDOT were greatly improved compared with that of the homopolymer pTPhSNS-EDOT, showing a reasonable optical contrast of 40% (1100 nm), a fast response speed of 0.37 s (1100 nm) and a good electrochromic property. In the second part of this paper, by introducing different number of benzene to thiophene-carbazole-thiophene structural units, a new monomer with four thiophenes (BTCPh, BTCBPh) was also formed. Polymer films with cross-linking structure were formed by electrochemical polymerization of monomers at different sites. Similarly, the number of central benzene rings and the change of steric hindrance lead to different molecular configurations of monomers, resulting in the formation of different cross-linking structure polymers. The similar redox curves of the polymer films, pBTCPh and pBTCBPh, result in similar spectroelectrochemical properties and similar discoloration behavior. Kinetic results show that pBTCPh and pBTCBP have similar optical contrast at 410 nm, 660, 1100 nm. From the electrochromic response time, the response time of pBTCPh film is faster than that of pBTCBPh, especially at 660 nm. The response time of pBTCPh film is half of that of pBTCBPh film. From the scanning electron microscopy (SEM), this may be because pBTCPh film has a more loose packing mode than that of pBTCBPh film, which is advantageous to the electrochromic response time. In addition, compared with pBTCBPh, pBTCPh has a faster charge injection ability and can also accelerate the electrochromic response. In the third part of this paper, tetraphenylmethane is used as the intermediate. A new monomer structure (TPhTTh, TPhTBTh, TPhBTThBBr) is formed by still coupling of four benzene units into thiophene units. Because the outer structure is also four thiophene units, a polymer with cross-linking structure can also be formed by electropolymerization. The conjugate lengths of polymers formed by chemical polymerization are controllable, so the effects of different conjugate lengths on the electrochromic properties will also be studied in this section. From the electrochemical polymerization of the three monomers, it was found that TPhTTh could not form films effectively. TPhTBTh and TPhBTThBBr were well deposited on ITO, and the corresponding polymer films pTPhTBTh and pTPhBTThBBr were formed. The cyclic voltammetry and ultraviolet spectra of the polymer films showed that pTPhBTThBBr was more effective. The electrochemical spectra of the two kinds of polymer films show that the latter has more obvious spectral changes, while the latter has better electrochromic properties, high optical contrast 55% (1100 nm), fast response speed and good electrochemical stability. Electron microscopy showed that the latter film exhibited a relatively loose packing morphology, which may be an important reason for the better electrochromic properties of the latter. In addition, the pTPhBTThBBr film has a better conjugation level than the pTPhTBTh film, which may also be the reason for the better properties of the latter.
【学位授予单位】：浙江工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O633.5

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