Faculty of Chemistry, University of Wrocław, 14 F. Joliot-Curie Street, 50-383 Wrocław, Poland.
J Phys Chem B. 2010 Jun 3;114(21):7158-71. doi: 10.1021/jp100796a.
Conditions of electrodeposition, i.e. a potential window of the process, addition of water, the current density, and morphology of substrate electrodes (Pt, Pt/TiO(2), Au), were shown to influence strongly ion-exchange properties of polypyrrole (PPy) synthesized in propylene carbonate (PC), doped with ClO(4)(-) or p-toluenesulfonate (TOS(-)). "Electrochemical porosity" and redox activity of PPy films were compared to the characteristics of poly(3,4-ethylenedioxythiophene) (PEDOT). A molecular indicator of the PPy film structure packing was bis(trifluoromethylsulfonyl)imide anion (TFSI(-)). Ion-exchange properties of PPy were found to be almost independent of chemical composition of the polymer, described in the literature as PPy(I), PPy(II), PPy(III). Instead, micro- and nanoscopic morphology of the polymer film and a molecular level packing of the polymer chains as well as the counterion nature are of the foremost importance. The polymer film structure/properties are shown to change upon prolonged redox/ionic stimulations. Lithium exchange between PPy films and contacting phases (PC electrolyte, TiO(2)) proceeds in addition to the anion exchange, the latter being a dominant process under conditions of the reversible electrochemical p-doping of PPy, although diffusion coefficients of PC solvated lithium ions in PPy are higher than diffusion coefficients of perchlorate, p-toluenesulfonate or bis(trifluoromethylsulfonyl)imide anions. The highest flux of Li(+) ions into/out of the PPy phase takes place about -1.0 V vs Ag/Ag(+) which is clearly evidenced by the cathodic/anodic CV peaks. Cation transport phenomena can be analyzed independently from anion transport when observed at a longer time scale (low values of potential scan rate) as each prevails at different redox states of the polymer. However, in a shorter time scale (v > or = 10 mV s(-1)), the opposite fluxes of cations and anions were observed to interfere. Furthermore, a net uptake of propylene carbonate by the as grown PPy film occurs at initial cycles of the cation uptake causing irreversible swelling of the polymer phase. Mechanisms of the redox process and accompanying mass transport involving PPy films were investigated using comparatively three techniques: cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and electrochemical quartz crystal microbalance (EQCM).
电沉积条件，即过程的电位窗口、水的添加、电流密度以及基底电极的形态（Pt、Pt/TiO(2)、Au），强烈影响在碳酸丙烯酯（PC）中合成的掺杂 ClO(4)(-)或对甲苯磺酸盐（TOS(-)）的聚吡咯（PPy）的离子交换特性。与聚（3,4-亚乙基二氧噻吩）（PEDOT）相比，比较了 PPy 薄膜的“电化学孔隙率”和氧化还原活性。聚吡咯膜结构堆积的分子指示剂为双（三氟甲基磺酰基）亚胺阴离子（TFSI(-)）。PPy 的离子交换特性几乎与文献中描述的 PPy(I)、PPy(II)、PPy(III)的聚合物化学组成无关。相反，聚合物膜的微观和纳米形貌以及聚合物链的分子水平堆积以及抗衡离子的性质是最重要的。研究表明，聚合物膜的结构/性质会在长时间的氧化还原/离子刺激下发生变化。在 PPy 薄膜与接触相（PC 电解质、TiO(2)）之间进行的锂交换除了阴离子交换之外还进行，尽管 PC 溶剂化锂离子在 PPy 中的扩散系数高于高氯酸根、对甲苯磺酸盐或双（三氟甲基磺酰基）亚胺阴离子的扩散系数，但在 PPy 的可逆电化学 p 掺杂条件下，后者是主要过程。在 -1.0 V 相对于 Ag/Ag(+)时，Li(+)离子进出 PPy 相的最大通量最高，这一点可以通过阴极/阳极 CV 峰清楚地证明。当在较长时间尺度（较低的电势扫描速率值）观察时，可以独立于阴离子传输来分析阳离子传输现象，因为在聚合物的不同氧化还原状态下，每个状态都占主导地位。然而，在较短的时间尺度（v >或= 10 mV s(-1)），观察到阳离子和阴离子的相反通量相互干扰。此外，在阳离子吸收的初始循环中，生长的 PPy 膜吸收了丙烯碳酸酯，导致聚合物相的不可逆溶胀。使用比较三种技术研究了涉及 PPy 薄膜的氧化还原过程和伴随的质量传输机制：循环伏安法（CV）、电化学阻抗谱（EIS）和电化学石英晶体微天平（EQCM）。
