Conductivity and Solubility of Py-MMA Copolymers Doped with Organic Protonic Acid in Two-Phase Solution

PPy(polypyrrole) has been a kind of widely used electrical polymer during the last few decades, owing to its excellent conductivity. However, the processing of PPy materials is still very difficult. Enhancing the solubility of PPy may provide a solution to improve such issue. In this paper, PPy was synthesized by chemical oxidation method, four kinds of organic protonic acid were used as dopant and FeCl₃ was used as oxidant. Several factors which might cause fluctuation of electrical conductivity, including the type of dopant, reaction temperature, dosage of dopant and oxidant, duration of reaction, and significance testing, were investigated and analyzed under orthogonal experiments, leading to influence order from significant to indistinctive as usage of dopant, usage of oxidant, reaction temperature, reacting duration, and kind of dopant. On this basis, Py and methyl methacrylate (MMA) were copolymerized in a two-phase solution to prepare soluble Py-MMA copolymers dissolving in ethyl acetate. Furthermore, factors including dosage of dopant, oxidant and MMA monomer, reacting temperature were analyzed to reveal the variations of conductivity and solubility. The results indicated that using organic protonic acids to dope PPy enhanced its conductivity, the optimal condition was associated with the using of TsOH, n(Dopant)∶n(Py)=1∶3, n (Oxidant)∶n(Py)=1∶3, 12-hour-reaction. Interestingly, as compared to PPy, the solubility of Py-MMA copolymers was obviously enhanced. The optimal conditions were at a temperature of 40 ℃, n(MMA)∶n(K₂S₂O₈)∶n(Py)∶n(TsOH)=2∶3∶6∶4, 4-hour-reaction. In this way, the solubility of the prepared Py-MMA copolymers was 5.56 g in ethyl acetate (70 ℃), and corresponding surface resistance was 0.76 Ω·cm.