Optimization of nanoemulsion preparation process using response surface methodology and its application in the synthesis of nano polypyrrole electrode materials

Abstract

Oil-in-water nanoemulsions as “nanoreactors” demonstrate application potential in constructing conductive polymer-based nanofunctional materials. This study introduces response surface methodology (RSM) to optimize the preparation process of the blank nanoemulsion, which is further used to synthesize polypyrrole (PPy) electrode materials. The blank nanoemulsions were prepared via a phase inversion emulsification method using a cyclohexane/Span 80-Tween 80/water system. A three-factor, three-level Box-Behnken design (BBD) was employed to reveal the dominant effect on the average droplet size of the nanoemulsion. Under conditions of an oil-to-emulsifier mass ratio of 2:1, an oil-to-water mass ratio of 1:10, and an emulsification temperature of 60 °C, a blank nanoemulsion with an average particle size of 130.3 ± 10 nm and an emulsification index of 99% was prepared. Utilizing this blank nanoemulsion as a confined reaction medium, nano-PPy electrode materials were synthesized via nanoemulsion polymerization. It was found that when the pyrrole (Py) monomer addition is less than 20 wt% of the dispersed phase, the Py has little impact on the properties of the original nanoemulsion system. The prepared spherical nano-PPy exhibits a specific surface area of 79.2 m² g⁻¹ and a particle size of ~ 100.0 nm, with a relatively narrow particle size distribution. Electrochemical test results indicate that the nano-PPy exhibits a specific capacitance of 153.4 F g⁻¹ at a current density of 0.5 A g⁻¹. After 2000 charge–discharge cycles, the capacitance retention rate is 63.6%, higher than other traditional in situ polymerization methods. This study provides new insights into the synthesis of conductive polymer electrode materials.

Graphical abstract