Electrochromic polyiminocarbazolylenes with latent hydrogen bonding
Electrochromic polyiminocarbazolylenes with latent hydrogen bonding
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DOI：
10.1039/c5py00713e
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发表时间：
2015-06
影响因子：
4.6
通讯作者：
B. Berns;B. Tieke
中科院分区：
文献类型：
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作者：
B. Berns;B. Tieke
通过钯催化的偶联反应，制备了主链或侧链上含有咔唑（cbz）单元和可热裂解叔丁氧羰基（boc）基团的聚亚氨基芳撑。由2，7-二溴-9-（2-乙基己基）-咔唑M1和9-（4-氨基苯基）咔唑盐酸盐M3（P1-EH）、2，7-二溴-9-叔丁氧基羰基-咔唑M2和M3（P1-BOC）、M1和4-叔丁基苯胺M4（P2-EH）或M2和M3（P2-BOC）制备聚合物。在180 °C下热处理boc取代的聚合物P1-BOC和P2-BOC多4小时导致boc基团的去除和由于氢键合（“潜在氢键合”）而对基底具有强粘附性的不溶性聚合物P1-H和P2-H的形成。对于P1-BOC，脱保护的速率常数k可以确定为约0.050 min-1。尺寸排阻色谱表明，聚合物的分子量在14 100和28 100 g mol-1之间。聚合物P1-EH、P1-BOC、P2-EH和P2-BOC易溶于甲苯、THF、二氯甲烷、氯仿和苯，而不溶于丙酮和甲醇。除去boc基团后，所得的P1-H和P2-H的聚合物膜不溶于普通有机溶剂。研究了聚合物的光学和电化学性能。由于主链中的富电子氮原子，聚合物可以容易地被氧化。氧化开始于约0.31 V vs. SCE，形成阳离子自由基。进一步的氧化发生在0.55 V与形成的dications，并在0.71 V与氧化的主链cbz单元。在约IV下，侧链cbz单元被氧化。该聚合物是电致变色的，并且表现出从无色经由橙子到绿色和蓝色的颜色变化。Cbz在电位≥0.71 V时发生氧化反应，导致二聚体的生成。由于聚合物链之间以及聚合物和ITO-基底之间的咔唑N-H-基团的氢键，boc基团的热裂解导致P1-H和P2-H的良好粘附的膜。发现P1-H在可逆氧化和粘附方面的最佳性能。该聚合物具有可逆的电致变色性，在900 nm处的对比度为12%，开关时间为400 ms。
Polyiminoarylenes with carbazole (cbz) units in the main chain, or main and side chain and thermally cleavable t-butyloxycarbonyl (boc) groups were prepared upon palladium-catalyzed coupling reactions. Polymers were prepared from 2,7-dibromo-9-(2-ethylhexyl)-carbazole M1 and 9-(4-aminophenyl)carbazole hydrochloride M3 (P1-EH), 2,7-dibromo-9-t-butyloxycarbonyl-carbazole M2 and M3 (P1-BOC), M1 and 4-t-butylaniline M4 (P2-EH), or M2 and M3 (P2-BOC). Thermal treatment of boc-substituted polymers P1-BOC and P2-BOC at 180 °C for ≥4 h led to removal of the boc groups and formation of insoluble polymers P1-H and P2-H with strong adhesion to the substrate due to hydrogen bonding (‘latent hydrogen bonding’). For P1-BOC the rate constant k of deprotection could be determined to be about 0.050 min−1. Size exclusion chromatography indicated that the molecular weights of the polymers were between 14 100 and 28 100 g mol−1. Polymers P1-EH, P1-BOC, P2-EH and P2-BOC were readily soluble in toluene, THF, dichloromethane, chloroform, and benzene, and insoluble in acetone and methanol. After removal of the boc groups the resulting polymer films of P1-H and P2-H were insoluble in common organic solvents. Optical and electrochemical properties of the polymers were investigated. Due to the electron-rich nitrogen atoms in the main chain, the polymers can be easily oxidized. Oxidation starts at about 0.31 V vs. SCE with formation of cation radicals. Further oxidation occurs at 0.55 V with formation of dications, and at 0.71 V with oxidation of main chain cbz units. At about 1 V the side chain cbz units are oxidized. The polymers are electrochromic and exhibit color changes from colorless via orange to green and blue. Cbz oxidation at potentials ≥0.71 V leads to the formation of dimers in a side reaction. Thermal cleavage of the boc groups leads to well-adhering films of P1-H and P2-H due to hydrogen bonding of the carbazole N–H-groups between polymer chains, and polymer and ITO-substrate. The best performance with regard to reversible oxidation and adhesion was found for P1-H. For this polymer a reversible electrochromism was found. A contrast ratio of 12% at 900 nm, and a switching time of 400 ms were determined.