Macromolecular Synthesis by Air Oxidative Polymerization through Multi-electron Transfer

研究氧的四电子还原成水不仅对于确定其寿命机理，而且对于制备新型催化剂具有重要意义。钴双核卟啉(CoP2)作为一种面对面的催化剂，被认为是促进该反应的优良催化剂。在该电极上制备了CoP2与聚苯胺的聚合物络合物。研究了聚苯胺-CoP2络合物的电化学性质，结果表明，与CoP2修饰电极相比，聚苯胺-CoP2络合物对4-电子还原的催化效率为80%，而CoP2修饰电极的催化效率为50%。为了确定提高CoP2催化效率的关键因素，人们合成了各种导电聚合物，包括自掺杂聚苯胺和质子转移氧化还原聚合物。探讨了4电子还原效率强烈依赖于聚合物基质的氧化还原电位，表明聚合物的氧化还原电位是该催化体系的重要影响因素。由于PCaN在较宽的pH范围内具有稳定的氧化还原活性，即使在中性条件下也是一种有效的电子媒介，因此在中性条件下(pH=6.2)，PCaN-CoP2络合物催化氧还原。RDV和RRDV测量表明，该催化剂对氧的4电子还原反应的催化效率高达95%。RRDV发生的是一步四电子还原，而不是两步两电子转移。这是因为PCAN在聚合物基质中具有酸性结构域，这被认为在一定程度上保持了薄膜的酸性，即使在中性条件下，氧的4电子还原也在中性条件下发生。

Research of the four-electron reduction of oxygen to water is important in order not only to determine the life mechanism but also to make novel catalysts.As face-to-face Cobalt Dinuclear Porphyrins (CoP2) are known as excellent catalysts to promote the reaction. Polymer complexes of CoP2 with Polyaniline were prepared on the electrode as a catalyst. Electrochemical properties of Polyaniline-CoP2 complex was investigated and proved to catalyze 4-electron reduction by 80%, compared to 50% by CoP2 modified electrode. In order to establish essential factor to promote catalytic efficiency of CoP2, various conducting polymers including self-dope polyaniline, and proton transfer redox polymer were synthesized. It probed that the efficiency of 4-electron reduction is strongly dependent on the redox potential of the polymer-matrix, indicating that redox potential of polymer is an important factor in this catalytic system. As PCAn acts as an efficient electron mediator even in neutral conditions due to its stable redox activity over wide pH range, catalytic reduction of oxygen was carried out using PCAn-CoP2 complex in neutral conditions (pH=6.2). A catalytic efficiency up to 95% toward 4-electron reduction of oxygen was observed by RDV, and RRDV measurements. One-step 4-electron reduction was occurred, not two steps 2-electron transfer by RRDV. It is because PCAn has acidic domain in the polymer matrix, which is thought to keep acidity in the film to some extent, even in neutral conditions, that 4-electron reduction of oxygen occurs in the neutral conditions.