【作者】 韦莉；

【导师】 陈奇；

【作者基本信息】 华东理工大学 ， 材料科学与工程， 2010， 博士

【摘要】 透明导电薄膜是一种非常重要的光电材料,它具有低电阻和高透光率的特点,可以被用于显示器、太阳能电池、抗静电涂层、带电防护膜等各种光电材料中。目前广泛研究和应用的透明导电薄膜主要为In2O3:Sn (ITO)、Sb:SnO2 (ATO)和ZnO:Al (ZAO)等无机氧化物透明导电薄膜。氧化物薄膜具有透光性好、电阻率低和化学稳定性较好等优点。但是作为无机材料,氧化物薄膜的脆性大、韧性差、合成温度高、且和柔性衬底的结合性较差,这些缺点限制了它们的进一步应用。例如,可折叠显示屏上要求透明导电薄膜具有可弯曲性,飞机有机玻璃窗户表面用于加热除霜的薄膜必须与有机基底结合牢固等。此外被广泛研究的导电材料还有高分子导电材料,包括聚苯胺、聚吡咯和聚噻吩等。其中聚苯胺由于在空气中的稳定性好、易加工、电导率易于调节等优点被广泛研究；但同时聚苯胺存在机械强度较低、耐热性差等缺点。因此考虑将聚苯胺导电材料掺杂入无机基体中,制备得到有机-无机杂化透明导电薄膜,就可以提高高分子导电材料的透光性、表面硬度以及热稳定性,获得韧性好、且和衬底结合性能好的透明导电薄膜。本文采用乳液聚合法制备十二烷基苯磺酸掺杂的导电聚苯胺(DBSA-PANI),并在此乳液系统中加入无机酸(盐酸、硝酸或硫酸)来调节乳液的酸度和结构,改善聚苯胺性能。然后将此聚苯胺通过溶胶-凝胶工艺与无机前驱体杂化,最终采用提拉法制备杂化透明导电薄膜。实验分别采用γ-缩水甘油醚氧丙基三甲氧基硅烷(GPTMS)和γ-巯丙基三甲氧基硅烷(MPTMS)为硅烷,研究了溶胶-凝胶中各成份和工艺对杂化薄膜性能的影响,并主要通过光谱分析研究材料的组成和结构。结果表明,通过在聚苯胺的乳液聚合体系中加入一定量的无机酸可以明显提高聚苯胺的导电性。当加入的无机酸浓度较小时,无机酸主要起到调节乳液酸度和结构的作用。随乳液中加入的无机酸浓度增大,材料导电性提高；但是当加入的无机酸浓度过大时,无机酸会和十二烷基苯磺酸(DBSA)形成竞争掺杂的关系,取代部分DBSA掺杂入聚苯胺链中,影响材料的稳定性。而且根据无机酸的体积和溶剂化效应的大小,掺杂入聚苯胺链的能力也不同。相对于体积较小的盐酸,较大体积的硫酸更容易掺杂入聚苯胺链中。因此,当在聚苯胺的乳液聚合体系中加入1.0 mol/L盐酸时,所得到的杂化薄膜的方块电阻最低。溶胶-凝胶过程中,各组份的含量决定了杂化材料性能和结构的稳定性。研究表明,在无水和乙醇的条件下,醋酸是硅烷发生水解和缩聚反应的反应剂和催化剂。在Y-缩水甘油醚氧丙基三甲氧基硅烷(GPTMS)为硅烷时,GPTMS有机链末端的环氧基在酸性条件下会开环形成羟基,有利于和聚苯胺反应,形成杂化结构。当醋酸与硅烷的摩尔比超过0.4后,会使硅烷的水解缩聚速率过快,造成与聚苯胺的掺杂速率不匹配,影响材料的稳定性。过多的醋酸还会引入较多的碳杂质,影响聚苯胺链中电子的传输,造成杂化材料导电性下降。间甲酚作为一种酸性溶剂,可以对聚苯胺进行二次掺杂,舒展聚苯胺的链结构,增强聚苯胺链中电子的离域性,提高材料导电性。但是由于其具有酸性,会对硅烷的水解缩聚反应起到催化的作用,同样会使硅烷的水解缩聚速率和聚苯胺的掺杂速率不匹配,影响杂化材料的结构。因此当醋酸和硅烷的摩尔比为0.4,间甲酚和硅烷的摩尔比为5时,能够得到结构稳定,且导电性和透光性都较好的杂化透明导电薄膜。同时,由于γ-巯丙基三甲氧基硅烷(MPTMS)有机链末端的巯基较容易被氧化形成磺酸基,因此可以对聚苯胺产生掺杂的作用。所以相对于GPTMS通过氢键作用和聚苯胺反应,MPTMS和聚苯胺形成的杂化结构更稳定,性能也较好。聚苯胺是杂化材料中的主要导电成份,研究聚苯胺含量对杂化薄膜结构和性能的影响的结果表明：聚苯胺含量增加会使无机网络更易形成二维网络结构,使材料的热稳定性下降。同时由于导电聚苯胺本身为酸性,对硅烷水解缩聚反应有催化作用,造成杂化结构不稳定。分别用GPTMS和MPTMS作为硅烷时,当聚苯胺含量为30wt.%时,杂化薄膜的方块电阻分别为5.1 kΩ/□和3.23 kΩ/□,可见光透过率可达80%。更多还原

【Abstract】 Transparent Conducting film is an important kind of photoelectric materials, with low resistance and high transparence. Transparent conducting films can be used in flat panel displays, low-e windows, photovoltaics, electrochromic devices and anti-static coatings. Many kinds of inorganic transparent conducting films have been investigated, such as In2O3: Sn (ITO), Sb:SnO2 (ATO) and ZnO:Al (ZAO). However, they have some disadvantages, for example, poor adhesion property on the flexible substrate, and hard to be deposited on the polymer substrate due to the high synthetic temperature, which limit their further applications. Conducting polymer is also an important kind of conducting materials. Among various conducting polymers such as polyaniline, polypyrrole and polythiophene, polyaniline is widely investigated due to its environmental stability, promising chemical, electrical and optical properties, as well as its unique redox tenability. However, poor mechanical properties and poor thermal stability have limited the applications of polyaniline. Composites incorporated by inorganic components and organic polymers can enhance the transparency, surface hardness and heat resistance of polymers.In this paper, dodecylbenzene sulfonic acid-doped polyaniline (DBSA-PANI) was synthesized via the emulsion polymerization, and inorganic acids (HC1, HNO3 or H2SO4) were added to adjust the structure of the emulsion system and improve the structure of polyaniline. Then, the hybrid sol solution was prepared by the obtained polyaniline and organoalkoxysiloxane through a sol-gel process. The transparent hybrid conducting films were deposited by dip-coating method. The organoalkoxysiloxanes used in the experiment were y-glycidoxypropyltrimethoxysilane (GPTMS) and y-(mercaptopropyl)trimethoxysilane (MPTMS), respectively. The effects of content of components of sol-gel solution on the properties and structure of the hybrid films were investigated by a combination of testing techniques.The results showed that the conductivity of DBSA-PANI was improved, when a certain concentration of inorganic acid was added into the emulsion system. Inorganic acid adjusted the acidity and structure of the emulsion solution at a lower concentration of inorganic acid. The conductivity of the hybrid films increased with an increase of concentration of inorganic acid added in the emulsion solution. However, the structure of the obtained samples was unstable, when the added concentration of inorganic acid was too high, because inorganic acid was incorporated into the polymer chains and became the main dopant for polyaniline. Furthermore, the influence of inorganic acid on the polyaniline chain was related with the bulk volumes and solvation of inorganic acid. Compared with hydrochloric acid, sulfuric acid was easier to replace the DBSA because it was more bulky. Sheet resistance of the hybrid films is lowest, when 1.0 mol/L HCl was added into the emulsion solution.The properties and structure of the hybrid films were affected by the content of components in sol-gel process. Acetic acid was used to play both the roles of reagent and catalyst during the hydrolysis-condensation reaction of organoalkoxysiloxane, which replaced the water and ethanol. When GPTMS was used as organoalkoxysiloxane, the epoxy ring of GPTMS can form a hydroxyl group in acid condition, which is beneficial to the disperseion for DBSA-PANI into the inorganic structure. When the molar ratio of HAc to organoalkoxysiloxane was higher than 0.4, the sturcure of the hybrid films was unstable, since the hydrolysis-condensation reaction of organoalkoxysiloxane increased. Moreover, the content of C impurities increased with an increase of the content of acetic acid, which blocked the transfer of electron in the polyaniline chain and decreased the conductivity of the hybrid films. On the other hand, m-cresol can adjust the acidity of solution and it was also a secondary dopant for DBSA-PANI to enhance conductivity of the hybrid films. However, m-cresol, as a kind of acid solvent, also accelerated the hydrolysis-condensation reaction of organoalkoxysiloxane and affected the stable of the obtained samples. Thus, the better properties and structure of the hybrid films can be prepared with the organoalkoxysiloxane/HAc/m-cresol molar ratio of 1/0.4/5. Furthermore, when MPTMS was used as organoalkoxysiloxane, the mercapto group of MPTMS was easier to be oxidized to sulfonic acid group. Polyaniline can be doped with sulfonic acid group. Therefore, the structure of hybrid films was more stable, when MPTMS was used.DBSA-PANI was the main conducting component of the hybrid films. The effects of content of polyaniline on the structure and properties of the hybrid films were investigated. The results showed that, the inorganic network formed more linear structure with an increase in content of DBSA-PANI, which resulted in the thermal stability decreasing. Furthermore, polyaniline was acidic. The structure of the hybrid films were unstable with an increase of the content of polyaniline, since the hydrolysis-condensation reaction of organoalkoxysiloxane increased. Sheet resistances of GPTMS-PANI and MPTMS-PANI hybrid films were 5.1 kΩ/□and 3.23 kΩ/□, respectively, when the content of polyaniline was 30 wt.%. Visible light transmittance of the hybrid films reached 80%.更多还原