Molecular weight of polyaniline synthesized by oxidation of aniline with ammonium persulfate and with ferric chloride

David, Stephen Kamau; Nicolau, Y.F.; Mélis, Flavien; Revillon, A.

doi:10.1016/0379-6779(94)02385-c

Cited by 67 publications

(6 citation statements)

References 11 publications

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“…It was clear from this figure that R h increased up to 250 nm with the annealing temperature. The reduction of EB chain to LB should result in the decrease of R h , as reported by Davied et al, resulting from the chain flexibility and interchain hydrogen-bonding ability as discussed before. The increase of R h is in good agreement with the decrease of D 0 and R h of the annealed sample.…”

Section: Resultsmentioning

confidence: 54%

“…The net result is a more compact chain with faster D 0 . In addition, NMP is a better solvent for LB than EB because amine−amine interchain hydrogen bonding is weaker than imine−amine interchain hydrogen bonding, as confirmed by GPC studies. , Therefore, the k d value should increase with the reduction reaction. The small D 0 upon annealing can be assigned to the translational diffusion of large particles composed of many EB molecules by cross-linking reaction.…”

Section: Resultsmentioning

confidence: 92%

“…A representative set of data are shown in Figure a measured at θ = 30°, 90°, and 150°. In general, NMP is not a good solvent for EB because of the strong hydrogen bonding between amine and imine nitrogen atoms in the EB backbone. , For example, EB chains form aggregates in NMP solution as evidenced by a bimodal molecular weight distribution of EB chains based on the gel permeation chromatography data. , The aggregation of the EB chain in NMP has been detected by DLS as well as by GPC; it has been reported that dilute EB/NMP solutions have two relaxation modes, a fast mode and a slow mode. , A fast relaxation mode is attributed to the diffusion of a single polymer chain while a slow mode is due to large particles or aggregates, , complexation, or gelation , by (physical or chemical) cross-linking in the dilute regime. In the case of EB/NMP solutions, the slow mode corresponds to the peak related to the high molecular weight compounds confirmed by many GPC studies, as mentioned before.…”

Section: Resultsmentioning

confidence: 99%

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Annealing Effects of Dilute Polyaniline/NMP Solution

et al. 2000

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The annealing effects of a dilute polyaniline solution on chemical and physical properties were investigated. Emeraldine base (EB) of polyaniline prepared by the conventional procedure was dissolved in 1-methyl-2-pyrrolidinone (NMP). After heating at 60−140 °C for 2 h, the color of PANi solution changed from deep blue to various colors depending on the annealing temperature. This solution was filtered and cooled at −5 °C to preserve an undoped structure. Changes of physical and chemical properties were investigated using ultraviolet−visible (UV−vis), Fourier transform infrared (FT-IR) spectroscopy, electron spectroscopy for chemical analysis (ESCA), and dynamic light scattering (DLS). By contrast to the previously reported reductive reaction, we concluded that the annealing of dilute EB/NMP solution resulted in cross-linking. This was indicated by the decrease of the mutual diffusion coefficient at infinite dilution (D 0) and the increase in the apparent hydrodynamic radius (R h) of EB with the annealing temperature evidenced by the DLS and the increase of the cyclic-N portion from ESCA results. The annealing also produces a polyelectrolyte chain, supported by FT−IR and DLS measurements.

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Section: Resultsmentioning

confidence: 54%

Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

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Annealing Effects of Dilute Polyaniline/NMP Solution

et al. 2000

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“…The regular grain size (20−80 nm) could correspond to the extent of the catalytic action. Typical molar masses are close to 20 000 g mol -1 with extremal values of 5000 and 40 0000 g mol -1 , − which correspond to polymer lengths between 30 and 2000 nm. If we assume that the grain size is about the same order of magnitude than the observed section, we effectively obtain chain lengths close to 300 nm.…”

Section: Discussionmentioning

confidence: 96%

Study of Polyanilines by High-Resolution Electron Microscopy

1999

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A chemically prepared emeraldine chloride powder has been studied by high-resolution electron microscopy. Two kinds of grains with varying degrees of crystallinity were observed: (i) Rolled sheets (20−100 nm in diameter) (aggregates, disks, or ribbons ?) with an amorphous surface layer are identified as the EB-II polymer polymorph because of the centering of the cell and characteristic interreticular distances. A periodicity (∼5 nm) ascribed to the growth irregularity of the pristine polymeric aggregate is observed around the catalytic center. (ii) Crystalline grains (20−50 nm) exhibiting well-characterized 0.59-nm interreticular spacing are identified as the ES-I emeraldine salt. The interchain structural order appears stronger than the order along the polyaniline chain, according to the bond angle flexibility. The observed concentric nanostructure supports both the sketch of ordered islands and the paracrystal descriptions.

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“…Phenazine units can be converted into active sites of polymerization under the action of atmospheric oxygen, but in this case the reaction is slow. An exception is likely to be a combination of atmospheric oxygen with Fe 3+ which is known to catalyze oxidation processes (Davied et al 1995). There are other examples of fast passing the energy barrier of phenazine "germination" and acceleration of polymerization.…”

Section: The Overcoming the "Germination" Stagementioning

confidence: 99%