Dispersion Polymerization of Aniline in Different Media:  A UV−Visible Spectroscopic and Kinetic Study

Abstract

The course of dispersion polymerization of aniline using ammonium peroxodisulfate (APS) as initiator oxidant and poly(vinyl alcohol) as stabilizer in different media, viz., water (1 M HCl), water (pH ) 2.41, [aniline] ≡ [HCl]), and aqueous ethanol (1 M HCl), was followed spectrophotometrically. It was found that the absorption peak positions for the pernigraniline salt change markedly with change in acidity and [APS]/[aniline] ratio. The spectral shape also changes greatly when water is replaced by aqueous ethanol. The evolution of the spectra with time was used to generate rate curves which reveal the autocatalytic nature of the reaction. The activation energies of the reaction in the various media were evaluated for both the induction period and the polymerization period using the inverse of the times of these periods as representing average rates for the periods, respectively. The activation energies increase with decrease in medium polarity and/or acidity. These variations have been discussed.

In Situ Polymerized Polyaniline Films

“…also been reported by Chakraborty and Mandal (24,25). Gill et al (26) observed an increase in the oxidation rate after the introduction of nanocolloidal silica but no acceleration effect was found when poly(ethylene oxide)-based stabilizer was used.…”

Polyaniline Morphology and Detectable Intermediate Aggregates

“…Analysis of more than 20 sets of UV-Vis spectra showed the characteristic traces seen in Figure 2 [54] It is known that upon oxidation by APS, oligoanilines are rapidly protonated to form PNS, absorbing light at around 650-700 nm. [54]b As the reaction progresses, PNB (%550 nm) can be observed (at %40 min in our system) until the APS is consumed, as PNB react with aniline to form ES (47 min).…”

“…[49,50] As the oxidation state changes, the UV-Vis absorption peak strength and/or peak position changes. [51] Thus, UV-Vis spectroscopy is widely used for characterizing PANI and studying the reaction kinetics in both electrochemical [52][53][54][55] and chemical oxidative polymerization [56][57][58][59][60] systems. Since PANI solution have high extinction coefficients even at a very low concentration, dilute reaction mixtures are usually required for in situ UVVis studies.…”

“…Since the aniline monomer is colorless, studies of early steps in the polymerization are precluded; thus these in situ UV-Vis studies mainly capture the late and/or final stages of polymerization. [49][50][51][52][53][54][55][56][57] In this study, UV-Vis spectroscopy was used to probe intermediates development in the simplest aniline chemical oxidative polymerization systems using ammonium persulfate (APS) as oxidant. By varying the initial reactant concentrations and using appropriate dilution, we were able to use UV-Vis spectroscopy to study the reaction mixture from the onset of reaction to the final stage of the polymerization.…”

Preparation of polyaniline/phosphorylated poly(vinyl alcohol) nanoparticles and their aqueous redispersion stability

“…Among the aforementioned approaches, preparation of the colloidal PANI dispersion with the polymeric stabilizers is a widely accepted one. Poly(N-vinyl pyrrolidone), 19,20 poly (methyl vinyl ether), 21,22 poly(vinyl alcohol) (PVA), 23,24 poly[(N-vinylpyrrolidone)-co-(vinylalcohol)], 19 and poly(ethylene oxide) (PEO) 25 have been most frequently used as polymeric stabilizers for the colloidal PANI dispersions. Table 1 Correspondence concerning this article should be addressed to P. Liu at pliu@izu.edu.cn.…”