Efficient and Scalable Synthesis of Pure Polypyrrole Nanoparticles Applicable for Advanced Nanocomposites and Carbon Nanoparticles

Abstract

Pure polypyrrole (PPy) nanoparticles that are well-applicable for nanocomposite and nanocarbon precursor were productively synthesized by necessarily unstirred oxidative polymerization of pyrrole in acidic aqueous media at 0°C without any template. The species and concentration of acid and oxidant have been carefully investigated to optimize the polymerization yield, conjugated structure, size, and conductivity of the PPy particles. Laser particle-size analysis, field-emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy all revealed that the PPy particles produced in still acid media have narrow size distribution and uniform spheroid morphology. Homogeneous nucleation and static repulsion are proposed as the formation and self-stabilization mechanisms of the PPy nanoparticles. Combination of HNO 3 medium and (NH 4 ) 2 S 2 O 8 oxidant is optimal for the synthesis of PPy nanoparticles possessing maximal yield of 87.2%, small diameter, and high conductivity which has been confirmed by a strong UV-vis band due to a large π-conjugated chain structure. This quiescent polymerization could be simply scaled up or down to synthesize a larger or smaller amount of PPy nanoparticles without compromising their yield, structure, and properties. Furthermore, the conductivity of the nano-PPy could reach 2.8 S/cm upon doping in 2.0 M HClO 4 . Simultaneous thermogravimetry-differential thermal analysis technique demonstrates that the PPy nanoparticles at 1000°C can be efficiently carbonized into carbon nanoparticles with narrower size distribution, smaller diameter of 62 nm, and much higher conductivity of about 21 S/cm. In particular, the conductivity will dramatically be enhanced to 219 S/cm and even 370 S/cm at the carbonization and graphitization temperatures of 1300 and 2300°C in nitrogen and argon, respectively. A conductive nano-PPy/cellulose diacetate nanocomposite film with low percolation threshold down to 0.2 wt %, good conductivity stability for at least 8 weeks, and potential bioapplicability was simply fabricated. The present synthesis requires no external templates and provides a facile and direct route to scalable synthesis of PPy exclusive nanoparticles with high yield, controllable size, strong re-dispersibility, high purity, adjustable conductivity, and high nanocarbon yield.

Effect of Process Parameters on the Synthesis of Polypyrrole by the Taguchi Method

“…From Figure 2 (b), when the molar ratios increased from 1:1 to 5:1, the particle size of PPy decreased first from 0.98 µm to 0.53 µm and then increased again (0.84 µm). This is consistent with the finding of Li et al [27]. They emphasized that at a lower concentration of oxidant, less Py radicals are formed, the polymerization process is slow, and thus smaller particles are formed.…”

“…The product yield increased from 0.06 g to 0.54 g as the molar ratios of oxidant to pyrrole increased from 1:1 to 5:1. The same observation was also found by Li et al [27] for the polymerization of PPy using APS as the oxidant. They also noted that the amount of oxidant required to produce sufficient PPy particles is at least equal to the monomer (molar ratio of oxidant/monomer higher than 1).…”

“…When H 2 O 2 was used as the oxidant, it produced the lowest yield (0.23 g) and conductivity (0.02 S/cm) and the larger particles size (0.90 µm). The PPy synthesized using APS as the oxidant produced a higher yield than FeCl 3 and H 2 O 2 because APS has more oxidizability towards the pyrrole monomers than the other oxidants [19,27]. The high conductivity obtained with FeCl 3 as the oxidant compared to APS and H 2 O 2 is due to the presence of iron ions.…”

Polypyrrole directly bonded to air-plasma activated carbon nanotube as electrode materials for high-performance supercapacitor

“…4 (b). According to Xin-Gui Li et al [29], the area ratio of the band at 1473 to the bond at 1555 cm -1 , A 1473 /A 1555 , is directly proportional to the extent of delocalization and conductivity. Polymers with short conjugation lengths show small values of A 1473 /A 1555 , whereas polymers with long conjugation lengths show large values and high conductivity.…”

Superhydrophobic Conducting Polymers Based on Hydrocarbon Poly(3,4‐Ethylenedioxyselenophene)

“…Indeed, five-ring heterocyclic polymers such as polythiophene, polypyrrole, polyfuran, and polyselenophene are of special interest worldwide, for example, for their optical and electrical properties. [19] With the electrodeposition process, it is possible to obtain highly structured surfaces with various surface morphologies, by controlling the electrochemical parameters or by tuning the monomer structure. [20][21][22][23][24] It is possible to introduce hydrophobic substituents (fluorine atoms or hydrocarbons), for example, by grafting on the monomer, which is a one-step process.…”