含芴聚合物电子亲合能和电离能的确定

通过循环伏安法测量了若干含芴交替共聚物的氧化还原电位,并通过氧化还原的起始电位点来确定聚合物的能级结构。从结果分析,在聚芴中引入系列的基团改变了聚合物的电离能、电子亲合能及带隙能。其中引入联吡啶后,带隙能变化不大,但电子亲合能明显升高,增加了电子的注入能力;引入带有七元环的联苯,特别是引入间位连接带有七元环的联苯后,带隙能明显增加。与聚芴比较,七元环聚合物电离能(I_p)从5.60eV增加到5.81eV,而电子亲合能(E_a)从2.05eV增加到2.42eV,带隙能从3.55eV增加到3.82eV。这与光谱得到的带隙能得到了较好的对应。

Electrochemical Determination of the Ionization Potential and Electron Affinity of PF Derivatives

Cyclic voltammetry measurements for the blue-emitting conjugated PF and its derivatives were reported . Both oxidation and reduction potentials onsets were determined and thus the ionization potentials I_p and electron affinities E_a of the polymers under the same experimental condition were estimated. The oxidative potential onset of PF was at 0.97 V and the reductive potential onset at -2.58 V. In order to increase the electron-accepting ability, the bipyridine units were introduced to the polymer backbone (PP). PP3(with 50% bipyridine content) displayed greater potential change in the reductive potential (-0.37 V) compared with PF because the bipyridine in PP3 is an electron-deficient. PP3 showed a good electro-accepted ability. The E_a was increased from the 2.05 eV to 1.92 eV compared with that of PF. In the anodic scan, the onsets of oxidation of PS, PO, PC and PD was at 1.10, 1.11, 1.10 and 1.06 V which correspond to the ionization potential (I_p) values of 5.73, 5.74, 5.73 and 5.69 eV.The electron affi- nity (E_a) values of the polymers were determined to be 2.16, 2.08, 1.92 and 1.96 eV. The incorporation of the seven-membered ring moiety into the polymer backbone led to wider bandgaps. It indicates that the seven-membered ring compound was an efficient segment for tailoring the band gap of the conjugated polymer. The shift of redox potential, change of the ionization potential and electron affinity were due to the different seven-membered ring structures. The band gap of the PF derivatives was increased by introducing the seven-membered ring, especially for the meta-linkage polymers. The electrochemical energy gap agrees well with the optical energy for these copolymers.