Aggregation and interchain “self” doping in emeraldine base

Long, S.M.; Brenneman, K.R.; Saprigin, A.; Kohlman, R. S.; Epstein, Arthur J.; Angelopoulos, Marie; Buchwalter, Stephen L.; Rossi, Angelo R.; Zheng, W.; MacDiarmid, Alan G.

doi:10.1016/s0379-6779(96)04157-4

Cited by 22 publications

(9 citation statements)

References 2 publications

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“…The dominant peak has a weight average M w related to the single chains of PANI and the other weak one has a higher M w attributed to the aggregation of EB PANI. 37 As shown in Figure 9, the values of the dominant peak of M w for all PANI samples obtained from case (C) are ranged around 12 000-22 000 with polydispersity values of around 4-6. This result is slightly smaller than that reported in previous studies (M w ¼30 000-70 000) 12,14 because of the relatively low [APS]/[AN] adopted in this study.…”

Section: Gpc and Tof-ms Resultsmentioning

confidence: 87%

Polymerization of aniline under various concentrations of APS and HCl

Tang

Wang

Lin

et al. 2011

Polym J

102

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Effects from various initial molar ratios of aniline (AN), ammonium peroxydisulfate (APS) and HCl ( [AN]: [APS]: [HCl]) on the polymerization of AN were investigated. First, a scheme derived from a molecular point of view was proposed to distinguish formation mechanisms based on their initial conditions. Thereafter, by choosing a relatively low ratio of Keywords: aniline; formation mechanism; phenazine-like oligomers; polyaniline INTRODUCTION Polyaniline (PANI) is one of the most important conducting and semi-conducting polymers widely used in organic optoelectronic devices and has attracted considerable attention recently because of its tunable electrical conductivity, easy preparation from common chemicals and excellent thermal and environmental stabilities. 1,2 The electrical properties of PANI are sensitively dependent on its oxidation and protonation states, of which the emeraldine state (see Figure 1) with a wide range of electrical conductivity can be achieved by simple doping/dedoping chemistry based on acidic/basic reactions. 1-3 The conventional chemical oxidative polymerization of aniline (AN) is carried out in a strong acidic solution and initiated by adding an oxidant (such as ammonium peroxydisulfate, APS). 3 From a technical point of view, the above-mentioned preparation for PANI is a simple process, but the formation mechanism involves an intricate interplay of consecutive chemical and physical reactions. [3][4][5][6][7][8][9][10][11][12] To account for the formation of PANI, the following basic mechanisms were reported. The redox reaction of neutral ANs with APS produces AN radicals. 4 Under a neutral or alkaline condition, the mixed ortho-para coupling of AN radicals together with oxidative intramolecular cyclization forms AN oligomers with phenazine-like structures at the initial stage (see Figures 2a and b for phenazine and phenazine-like trimer). 9-13 The oxidation of AN and AN oligomers with APS both release protons, and the pH of the solution falls. [12][13][14][15][16][17][18][19][20] In a strong acidic environment, the formation of a para-coupled structure

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Section: Gpc and Tof-ms Resultsmentioning

confidence: 87%

Polymerization of aniline under various concentrations of APS and HCl

Tang

Wang

Lin

et al. 2011

Polym J

102

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“…The presence of polarons may be explained by the fact that there could be some amount of the "self-doped" form in the PANI structure that contributes to the EPR signal [35,36]. It is known that the EB oxidation state of PANI consists of aggregates that are the result of interchain hydrogen bonding through the amine and imine nitrogen sites which, in addition, also give rise to a form of "interchain and intrachain self-doping" [35,36].…”

Section: Cp Mas Experiments: Pani Ebmentioning

confidence: 99%

“…It is known that the EB oxidation state of PANI consists of aggregates that are the result of interchain hydrogen bonding through the amine and imine nitrogen sites which, in addition, also give rise to a form of "interchain and intrachain self-doping" [35,36]. The decrease in the polaron concentration is due to the removat of the radical centers in the PANI (with the formation of DPPHH (Eq.…”

Section: Cp Mas Experiments: Pani Ebmentioning

confidence: 99%

Solid-state magnetic resonance studies of polyaniline as a radical scavenger

et al. 2005

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The first detailed study of polyaniline (PANI) and reduced PANI (R-PANI) before and after reaction with the stable organic free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH) by using solidstate 13C CP MAS (cross-polarization magic-angle spinning), NQS (nonquaternary suppressed) and CPPI (cross-polarization phase inversion) nuclear magnetic resonance teehniques is reported. These techniques reveal relatively subtle structural changes that occur upon reaction with DPPH free radicals and confirm the radical scavenging ability of PANI. The integrated intensity of the PANI CP MAS spectrum after reaction with DPPH is about 8% larger than that of PANI and this cannot be explained by an oxidation process alone. The increase is attributed to a decrease in the polaron concentration in the polymer, which is consistent with electron paramagnetic resonance (EPR) data that show a decrease of the EPR signal intensity after reaction of chemically synthesized PANI with DPPH.

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“…[5][6][7][8][9][10] However, control of crystalline order is non-trivial due to the inherent polydispersity and poor solubility in common solvents of π-conjugated polymers. The interactions between the polymer chain, dopant and solvent result in a range of unpredictable structural defects such as chain-coiling and entanglement, 11,12 self-doping 13 and phaseseparation of oxidation states, 14 all of which inhibit the mobility of charge through the polymer and reduce the observed conductivity. A number of strategies have previously been employed to enhance the degree of crystallinity and solution processibility of PANI.…”

Section: Introductionmentioning

confidence: 99%

Structured oligo(aniline) nanofilms via ionic self-assembly

et al. 2012

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Conducting polymers have shown great potential for application in electronic devices. A major challenge in such applications is to control the supramolecular structures these materials form to optimise the functionality. In this work we probe the structure of oligo(aniline) thin films (of subµm thickness) drop cast on a silicon substrate using synchrotron surface diffraction. Self-assembly was induced through doping with an acid surfactant, bis(ethyl hexyl) phosphate (BEHP), resulting in the formation of well-ordered lamellae with the d-spacing ranging from 2.15 nm to 2.35 nm. The exact structural characteristics depended both on the oligomer chain length and film thickness, as well as the doping ratio. Complementary UV/Vis spectroscopy measurements confirm that such thin films retain their bulk electronic properties. Our results point to a simple and effective ionic self-assembly approach to prepare thin films with well-defined structures by tailoring parameters such as the oligomer molecular architecture, the nanofilm composition and the interfacial roughness.

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Aggregation and interchain “self” doping in emeraldine base

Cited by 22 publications

References 2 publications

Polymerization of aniline under various concentrations of APS and HCl

Polymerization of aniline under various concentrations of APS and HCl

Solid-state magnetic resonance studies of polyaniline as a radical scavenger

Structured oligo(aniline) nanofilms via ionic self-assembly

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