Relationship between Chain Length, Disorder, and Resistivity in Polypyrrole Films

Abstract

The effects of the polymerization temperature and of voltammetric cycling on the chain length and the resistivity of polypyrrole films are investigated. The studies provide further proof for the existence of at least two different types of polypyrrole, the so-called PPy I and PPy II. As the electropolymerization of conjugated systems in contrast to normal polymerization reactions is a fully activated process, the generation of these different types of PPy depends on experimental parameters such as temperature or formation potentials. UV-vis measurements demonstrate that PPy II comprises significantly shorter chains than PPy I (8-12 vs 32-64 units); moreover, film conductivity is found to increase with the fraction of PPy II. This fraction is changed via the polymerization temperature as well as by cyclic voltammetry, both of which can induce a metal-insulator transition. The counter-intuitive relationship between resistivity and chain length is interpreted in terms of disorder-dominated transport, in which the shorter chains of PPy II support the formation of delocalized electronic states, thereby increasing the localization length. Thus, our results are in agreement with recent broadband reflectivity measurements.

Conjugated Polymer and Hybrid Polymer-Metal Single Nanowires: Correlated Characterization and Device Integration

“…This is coherent with the room temperature conductivity of ≈ 0.04 S.cm −1 and it is comparable to the bulk insulating PPy prepared under the same conditions. Several experimental studies have shown that the Mott variable-range-hopping (VRH) regime is an appropriate model of charge transport in CP NWs as it is well-known for bulk CPs [Aguilar-Hernández & Potje-Kamloth (1999);Park (2004); Bufon (2005)]. In this model, the charge transport is due to thermally activated tunneling among states that are localized in a constant density of states [Mott & Davis (1979)].…”

Enhanced electrocapacitive performance and high power density of polypyrrole/graphene oxide nanocomposites prepared at reduced temperature

“…Such an increase in the peak current was more pronounced for PNCs prepared at 10 ± 1°C over those prepared at 30 ± 1°C [13][14][15][16][17][18][19] (Fig. 7a).…”

“…The treated substrate was dried at room temperature for 2 h and then at 100°C/400 mmHg for 48 h. This afforded cathodes with a mass thickness of electroactive materials by 5 ± 1 mg over the 316-SS substrate [25]. low temperature liberates PPY nanoparticles [12] with improved specific and electrochemical conductivities [13][14][15][16][17][18][19].…”

Remotely Interrogated Passive Polarizing Dosimeter (RIPPeD).

“…Previous work on conductive polymers for optical applications has typically used one of three material systems: aniline 12,14-15 , thiophene [16][17][18] (used in spin coating work) or pyrrole [9][10][19][20][21] . In addition to the spin coating effort, our work has used electrochemically deposited polypyrrole, doped to provide high conductivity.…”

“…Previous work has used both potentiostatic [19][20] and galvanostatic 21,23 methods to control the growth of polypyrrole films. Samples were grown using both voltage and current control and it was determined that current control provided higher quality films.…”