Effect of alkyl chain length of dopant on properties of polyaniline

초록

We investigated the influence of alkyl chain length of dopants on the properties of polyaniline (PANi) when it was doped in m-cresol with various alkylbenzenesulfonic acids. The dopants were benzenesulfonic acid (BSA), p-toluenesulfonic acid (TSA), butylbenzenesulfonic acid (BBSA) and dodecylbenzenesulfonic acid (DBSA). In general, the solubility and electrical conductivity of doped PANi increased with longer alkyl chain length of dopants. When PANi was doped with bulky alkylbenzenesulfonic acid, the solubilities were more than 80 wt% because the bulky dopants decreased interactions between polymer chains. The solubility of PANi increased with longer alkyl chain length of dopants because the longer alkyl chain acted as a better surfactant and increased free volume between polymer chains. The electrical conductivities ranged from 3.4 to 110 S/cm. Conductivity also increased with alkyl chain length of dopants. The increased conductivity with longer alkyl chain length may be related to the increased doping level measured by electron paramagnetic resonance spectroscopy (EPR). Increased doping level may make intra-molecular conduction facile. Also electrostatic repulsion due to more polarons on the polymer chain may induce chain conformation into expanded coil. Thus, the conformational change will result in easier inter-molecular conduction.

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