Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
Langmuir. 2011 Jun 21;27(12):7776-82. doi: 10.1021/la102684d. Epub 2010 Nov 17.
With the use of the "falling pH" approach, the free floating films obtained at the air/liquid interface during aniline oxidative polymerization in the presence of hydrochloric acid have been reported and characterized for the first time. The surface of the films is compact and consists of small densely packed particles (around 10-20 nm in diameter). In addition to the free floating films the precipitation of various self-assembled nanostructures was also observed. The thickness of the films depends on the concentration of the reactants and ranges from 40 to 50 nm. Scanning electron microscopy (SEM) and transmission electron microscopy results imply that 3D nanostructures are physically adsorbed onto the film and that they represent two separated phases. Fourier transform infrared (FTIR) and UV-vis measurements have confirmed the presence of polyaniline and branched oligoanilines. On the basis of an orientation distribution of H(2)O and aniline molecules at the air/liquid interface and with the use of the cooperative effect of hydrogen-bond formation, a mechanism for film growth has been proposed. Three samples are synthesized in the presence of different acids-nitric, sulfuric, and acetic. The SEM and FTIR data showed similar morphologies and structural characteristics. This implies that the morphology and structure of the final products depend on the acidity conditions (pH) during the reaction rather than on the nature of the dopant acid.
采用“pH 值下降”的方法，首次报道并表征了在盐酸存在下苯胺氧化聚合过程中在气/液界面获得的自由浮动膜。膜的表面致密，由小而密集的颗粒（直径约为 10-20nm）组成。除了自由浮动膜外，还观察到各种自组装纳米结构的沉淀。膜的厚度取决于反应物的浓度，范围从 40nm 到 50nm。扫描电子显微镜（SEM）和透射电子显微镜结果表明，3D 纳米结构物理吸附在膜上，它们代表两个分离的相。傅里叶变换红外（FTIR）和紫外-可见测量证实了聚苯胺和支化寡聚苯胺的存在。基于在气/液界面上水和苯胺分子的取向分布，并利用氢键形成的协同效应，提出了一种薄膜生长的机制。在存在不同酸（硝酸、硫酸和乙酸）的情况下合成了三个样品。SEM 和 FTIR 数据显示出相似的形态和结构特征。这表明最终产物的形态和结构取决于反应过程中的酸度条件（pH 值），而不是掺杂酸的性质。
