Mixed alkylthiophene-based heterocyclic polymers containing oxadiazole units via electrochemical polymerisation: spectroscopic, electrochemical and spectroelectrochemical properties
作者:Alexander S. FisyukPermanent address: Department、Renaud Demadrille、Claudia Querner、Malgorzata Zagorska、Joël Bleuse、Adam Pron
DOI:10.1039/b415587d
日期:——
Symmetric alkylthiophene-based mixed heterocyclic trimer and pentamer, containing central oxadiazole units, have been prepared. Because of the electron-withdrawing properties of oxadiazole, the trimer cannot be electropolymerised and undergoes an oxidative-type destruction at high potentials. In contrast, the pentamer readily polymerises, giving a short chain polymer. Both trimer and pentamer exhibit strong photoluminescence with a maximum at 399 nm (13% quantum yield) and 467 nm (46% quantum yield), respectively. The polymer resulting from the electropolymerisation of the pentamer is also luminescent with the maximum of the excitation band at 528 nm (33% quantum yield). The polymer can be oxidatively doped as demonstrated by cyclic voltammetry, showing a clear anodic peak at 0.62 V versus Ag/Ag+ and its cathodic counterpart at 0.56 V, associated with the undoping process. The significantly higher potential of the oxidative doping of the prepared mixed heterocyclic polymer, as compared to the poly(alkylthiophene) homopolymer of similar molecular weight, is caused by the presence of the oxadiazole unit, which lowers the electron density in the π-electron system of the oligothiophene subunit and makes its oxidation more difficult. The spectroelectrochemical investigation of the polymer is consistent with its voltammetric behaviour, exhibiting doping-induced bleaching of the band originating from the π-π* transition and simultaneous growth of the bipolaron bands. The observed clear and reversible spectroelectrochemical behaviour makes the developed polymer a promising candidate for applications in electrochromic devices or electrochemical sensors.
已制备出含中心氧杂二唑单元的对称烷基噻吩基混合杂环三聚体和五聚体。由于氧杂二唑具有吸电子特性,三聚体无法电聚,在高电位下会发生氧化型破坏。相比之下,五聚体易于聚合,形成短链聚合物。三聚体和五聚体均具有强烈的光致发光特性,最大发光波长分别为399 nm(13%量子产额)和467 nm(46%量子产额)。五聚体电聚产生的聚合物也具有发光特性,激发带的最大波长为528 nm(33%量子产额)。循环伏安法表明,该聚合物可发生氧化掺杂,在0.62 V(相对于Ag/Ag+)时出现明显的阳极峰,在0.56 V时出现阴极峰,这与未掺杂过程有关。与分子量相似的聚(烷基噻吩)均聚物相比,所制备的混合杂环聚合物的氧化掺杂电位明显更高,这是由于氧杂二唑单元的存在降低了噻吩亚基π电子系统的电子密度,使其氧化更加困难。聚合物的光谱电化学研究结果与其伏安特性一致,表明掺杂导致π-π*跃迁产生的带出现漂白,双极子带同时增长。所观察到的清晰且可逆的光谱