【作者】 石家华；

【导师】 高青雨；

【作者基本信息】 河南大学 ， 高分子化学与物理， 2002， 硕士

【摘要】 在众多的导电聚合物研究中，聚噻吩在有机半导体、电导材料、电致发光材料等方面获得广泛应用，引起了人们的普遍关注。但是，在过去的研究中，对聚噻吩的研究主要是在有机体系中，更多的证据表明痕量水的存在对噻吩的电化学聚合是相当有害的，它大大降低了聚噻吩的有效共轭链长和电导率。离子液体作为一类新型的环境友好的“绿色溶剂”有其优异的性能，并在很多领域取得成功应用。在本论文中，我们第一次使用离子液体[BMIM]PF6既作为溶剂又作为支持电解质，在其中直接电化学聚合制备聚噻吩、聚(3—甲基噻吩)。 采用两步合成法合成了1—丁基—3—甲基咪唑六氟磷酸盐离子液体[BMIM]PF6，并用FT-IR、和1H-NMR对其进行表征，图谱分析的结果可以证实所合成的离子液体[BMIM]PF6的正确性。用循环伏安法研究了[BMIM)PF6的电化学活性，发现[BMIM]PF6具有宽阔、稳定的电化学电位窗(-2.0V～+2.5V)，同时测得其离子电导率为3.5×10-3 s/cm，介电常数为3.1×10-8 F/m，特征粘度为1.62ml/g。虽然粘度较大，因其良好的导电性和溶解性证明其可以作为电化学研究的良溶剂。 采用循环伏安法、恒电位阶跃法和恒电流阶跃法对不同浓度(0.02M，0.1M，0.2M，0.3M，0.5M)的噻吩单体在离子液体[BMIM]PF6中的电化学聚合研究发现，在一定条件下，噻吩单体能够在[BMIM]PF6中直接电化学聚合制备聚合物膜，[BMIM]PF6既是溶剂又是支持电解质。单体浓度低于0.1M时，难以得到聚合物膜。但单体浓度大于0.1M时，恒电位在1.7V～1.9V之间或恒电流在3.0mAcm-2～8.0mAcm-2之间进行调整均可以制得光滑均匀的兰绿色聚噻吩膜。随着噻吩单体浓度的增大，电流密度明显增大，开始氧化聚合的电位相应减小(0.1M时为+1.64V，而0.5M时为+1.54V)，而氧化聚合的峰电位明显正移(0.02M时峰电位是约+1.9V，0.5M时峰电位是+2.4V)，脱掺杂峰的电位发生负移，而掺杂峰在一宽阔的范围内变化不大。 用红外光谱对聚噻吩膜进行表征，发现1.8V下制备的聚噻吩有明显的特征峰，脱掺杂态聚合物膜790cm-1处的特征峰是2,5-取代β位的CH面外弯曲振动峰，证明聚噻吩主要是α—α’规则连接；1030，1120，1200，1340 cm-1四个吸收带为掺杂态特征峰。 用紫外—可见光谱研究聚噻吩膜的电子行为，刚制备的聚噻吩膜为掺杂态， 河南大学硕士学位论文呈现兰绿色，在740urn左右宽阔范围表现出特征吸收，这是掺杂态中极化子存在的结果。对掺杂态聚噬吩膜进行电化学还原脱掺杂处理，聚噬吩膜由兰绿色变成红色，740urn处吸收峰消失，而在490urn处表现出中性态的特征吸收，这是。一／跃迁的结果。重新将中性态聚噬吩膜电化学掺杂，聚噎吩膜在740urn处吸收峰重新出现。这是因为前线轨道间的能级间隙减小，反映在UV－VS光谱上就是最大吸收波长红移。 用扫描电子显微镜（SEM）观察聚噬吩膜的表面形貌，在不同聚合电位下制备的聚噬吩膜（同一厚度），随着聚合电位从1．6V到1．gV增大，膜的表面形态从疏松网状逐渐变得致密。在2．6V下，膜因过氧化而使表面变成紧密堆积的小块状，网状结构被破坏，聚噬吩膜失去导电性。在1．SV下恒电位聚合制备聚噬吩膜，随着膜逐渐变厚，膜表面形貌渐趋粗糙。掺杂态的膜表面为疏松的立体网络状，而脱掺杂态后，由于对阴离于的离去，聚合物链相互靠近堆积成致密的“菜花”状。 用循环伏安法对比研究0．SM的嚷吩单体在离子液体＊MIMPF对有机体系乙腊／TBAP凡中的电化学聚合，发现在离子液体＊MIMPF。中电聚合噬吩可以降低开始氧化聚合电位，更有利于避免高电位下聚合物膜过氧化的发生；在离子液体中制备的聚噬吩膜具有良好的稳定性。 将0．ZM的3－甲基噬吩加到离子液体pMIMPF6和乙脂／①…刑PF6（．IM）中分别进行电化学聚合。在离子液体＊ PF6中，3－甲基噬吩在十1．45V开始氧化聚合，在＋二刀V出现氧化聚合峰，在＋0．gV和＋0．3V出现一对氧化还原峰分别对应的是聚门－甲基噬吩）的掺杂和脱掺杂现象；而在乙睛／（Bul4NPF6．IM冲，直到＋1．75V才开始发生氧化聚合反应，聚门－甲基噬吩）的氧化还原峰出现在十0＊gV和 ＋0．75V。对聚门－甲基噬吩）膜进行电活性研究，证明在离子液体［BMIMIPF。中电化学制备的聚（3一甲基噬吩）膜的稳定性非常好。紫外一可见光谱研究发现，从中性态到掺杂态转移的特征吸收非常明显。用SEM观察膜的形貌发现，随着膜逐渐变厚，表面形貌渐趋粗糙。从掺杂态到脱掺杂态。表面形貌由疏松交织网状结构变得相对致密。 但是，很遗憾的是我们在离子液体田MIMIPF6中直接电聚合制备的聚合物膜的导电率偏低（在 0．01—0．Is／cm之间），可能与离子液体粘度大和掺杂的对阴离于偏少有关。更多还原

【Abstract】 Among many conducting polymers, polythiophene(PTh) has drawn much attention in recent years because of its attractive applications such as conductors, electrode materials, and organic semiconductors. However, PTh is generally synthesized by electrochemical oxidation of the monomer in an organic medium. More evidences showed that trace water was harmful to the electropolymerization of thiophene and reduced the efficient conjugated chain length and conductivity of PTh films. Ionic liquids are a class of novel environmentally benign "green solvents" that have remarkable properties and promising applications in many fields. In this thesis, we report for the first time on the direct electropolymerization of thiophene and 3-methylthiophene in l-butyl-3-methylimidazolium hexafluorophosphate ionic liquid ([BMIMJPFe) used as solvent and electrolyte.The ionic liquid [BMIM]PF6 was synthesized with two steps and was characterized by FT-IR^H-NMR^V. [BMIM]PF6 took on a wide and stable electrochemical window (ca. 4.5 V);It’s conductivity was 3.5*10"3 s/cm; dielectric constant is 3.1 xlO"8 F/m, and characteristic viscidity is 1.62ml/g. Although it’s viscidity is rather high, [BMIMJPFg could be used as fine solvent in electrochemistry because of it’s conductivity and solvation.The electrochemical polymerization of thiophene monomer with the different concentration (0.02M, 0.1M, 0.2M, 0.3M, 0.5M) in ionic liquid [BMIM]PF6 has been studied using cyclic voltammetry, potentiostatic steps and galvanostatic steps. When the monomer concentration was lower than 0.1M, it’s hard to obtain polymer films. When the monomer concentration was higher thanO.lM, it was found that very homogeneous and blue-green films were obtained when the potential for electropolymerization was controlled between +1.7 V and +1.9 V or the current density was between 3.0 mA cm"2 and 8.0mA cm"2. When the monomer concentration increased, the current density also increased evidently, and the oxidation potentials of the monomer decreased (+ 1.64V at 0.1M, but + 1.54V at 0.5M), but the oxidation peak potentials of the monomer shifted to larger potentials (ca. +1.9V at 0.02M, but ca. +2.4V at 0.5M); the reduction peaks (de-doping) shifted largely to smaller potentials; but the oxidation peaks (doping)didn’t change too much at a broad range.PTh films obtained electrochemically under 1.8V were characterized by IR. The band at 790cm"1 of the dedoped polymer films is attributed to the out-of-plane vibration of C-H on the p-position of 2,5-disubstituted thiophene. These results indicate that the PTh films polymerized in ionic liquid is dominantly a ?a ’ linked. Four intense bands at 1030, 1120, 1200 and 1340 cm"1, are the bands of doped polythiophene from the vibration of charge transfer conjugated thiophene rings or a charged polaron.The UV-Vis spectrum of polythiophene films show that the bands at 740nm, as observed from an as-grown polythiophene film, may be assigned to a bipolaron. When the doped polythiophene films were electrochemically reduced, polythiophene films turned red from blue-green, and the bands at 740nm disappeared; however a new band appeared at 490nm, characteristic of a n ?JT transition of conjugated polymer chain. After neutral PTh films were electrochemically redoped, the band at 740nm appeared again. This is because the originally filled valence band of the polymer becomes partially empty and the Fermi level lowers to the valence band, resulting in red-shift of the most absorption band.SEM photographs of PTh films (same thickness) electrochemically prepared under different potential change from loosen meshwork to compact meshwork with increasing of potential (from 1.6V to 1.9V). PTh films obtained under 2.6V change to compact cumulate clump structure because of overoxidation. The as-grown PTh film (prepared at +1.8V) is blue-green with a metallic luster, exists as loose solid meshwork; however the dedoped film changes to a compact "cauliflower" structure. This is probably because the departure of opposite anion caused closing up of更多还原