Experimental Evidence for Hydrogen Bonding in Polyaniline:  Mechanism of Aggregate Formation and Dependency on Oxidation State

Abstract

Aggregation in the nondoped polyaniline, emeraldine base (EB), as observed by GPC in a N-methyl-2-pyrrolidinone (NMP) solution, was found to be closely related to the fraction of the imine nitrogen atoms in the nondoped polymer, i.e., to the oxidation state of the polymer. As EB was reduced to leucoemeraldine base (LEB), the degree of aggregation was significantly reduced. The results of gel permeation chromatography (GPC) and infrared studies suggest that the aggregation of the polymer is due to interchain hydrogen bonding between the imine and amine nitrogen sites on adjacent polymer molecules. The degree of hydrogen bonding and, thus, aggregation found in the polymer is greatly affected by solvents, LiCl, and the oxidation state of the polymer.

The electrochemical deposition of polyaniline at pure aluminium: electrochemical activity and corrosion protection properties

“…Furthermore, the distribution of molecular masses, recorded for the aluminium and platinum system were very similar to the measurements made by MacDiarmid and co-workers [17,18] on chemically synthesized polyaniline. In both studies a bimodal distribution, Fig.…”

“…The presence of the first peak, i.e. the high molecular weigh fraction, has been attributed to aggregates of polymer chains linked through hydrogen bonding, This aggregation is the result of inter-chain hydrogen bonding between the amine and imine nitrogen atoms in the polyaniline backbone [17,18]. These data are similar to those reported by MacDiarmid and co-workers [17] for chemically synthesized polyaniline in the emeraldine base state.…”

“…5 for the polyaniline deposited at the aluminium sample. The characteristic bimodal molecular weight distribution, which has been reported previously for polyaniline, in the form of the emeraldine base [17,18], is evident. The presence of the first peak, i.e.…”

Filmes poliméricos ultrafinos produzidos pela técnica de automontagem: preparação, propriedades e aplicações

“…Stockton e Rubner 28 verificaram que a quantidade de polianilina adsorvida num filme automontado é maior quando camadas desta são alternadas com camadas de polímeros que têm facilidade de fazer ligações de hidrogênio. Isto se deve ao fato de as cadeias de polianilina não dopada assumirem uma conformação mais enovelada, até mesmo formando agregados na solução 32 , ocupando menos espaço no substrato e facilitando a aproximação e acomodação de mais polímero. Mais ainda, Pontes e colaboradores 29 verificaram que no caso da polianilina o processo de adsorção pode independer da deposição alternada de policátions e poliânions, uma vez que o polímero desprotonado pode ser adsorvido sobre si próprio em situações especiais, principalmente quando o procedimento de lavagem entre cada camada não é realizado.…”

Influence of the pH and substrate immersion time on the adsorption of poly(o-ethoxyaniline) in self-assembled films

“…At high pHs the POEA chains not significantly protonated will adsorb mainly through hydrogen bonding, via amine and imine sites, in agreement with the literature. [13][14][15]20 Hydrogen bonding allows the polymer to adsorb over itself without saturation under the conditions studied in Figure 2b and c. At low pHs although the hydrogen bonding might be also acting on the adsorption, the large number of protonated nitrogen atoms from POEA chains already attached would repel upcoming chains inducing an earlier interruption of the adsorption process.AFM images of POEA films obtained in two different time scales of substrate immersion, at pH 5, are presented in Figure 3. The AFM image of a clean quartz substrate without any film deposited (Figure 3a) reveals a globular morphology with very low roughness.…”