The azobenzene-containing main-chain ferrocene-based polyesters were also found to display bathochromic shifts upon the addition of HCl due to the formation of the azonium ions that make these polymeric species good candidates as pH indicators. 这种主链含偶氮苯的二茂铁基聚酯同时被发现显示出在HCl的存在下出现红移,这是因为在盐酸的存在下形成了离子,这种现象使这种聚合物有可能成为pH指示剂很好的候选材料。