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A comparative study of the effect of graphene admixture to polyaniline hole-injection layers of polymer light emitting diodes (PLEDs) and anode buffer layers of organic solar cells (OSCs) has been performed. The layers have been made from the complex of polyaniline with poly-2-acrylamido-2-methyl-1propanesulfonic acid with (or without) addition of 1 wt % graphene prepared by the mechanochemical method. It has been shown that the effects of the graphene addition into the auxiliary PLED and OSC layers are opposite: performance characteristics (current and light efficiency) of the former deteriorate and those of the latter are improved (in particular, the powerconversion efficiency increases by a factor of 1.4). The reasons considered to be behind the opposite effects are a significant difference in the currents flowing through the PLED and OSC, a more developed interface between the OSC anode buffer layer and photolayer, and channeling the longitudinal conductivity at the interface between graphene nanoparticles and polyaniline.

Despite the significant interest in poly(sulfonic acids) as proton conductors and acid catalysts, their dissociation behavior is poorly studied. The influence of the polyelectrolyte effect on the dissociation of the strong poly(acid) is frequently neglected. Moreover, the decrease in distance between the sulfonic groups is thought to enhance the acid strength or charge carrier concentration. Using simple and reliable methods (pH measurements and potentiometric titration), it is demonstrated that a strong poly(sulfonic acid) such as poly(2-acrylamido-2-methyl-1-propanesulfonic acid) displays a “limited” (predicted by the Manning-Oosawa theory) degree of dissociation in a salt-free solution and “maximal” degree of dissociation equivalent to the monomer analog in the presence of NaCl excess.

Electrodeposition of polyaniline (PANI) complexes with a polymeric sulfonic acid of variable molecular weight has been studied with the purpose to explain specific features of aniline electropolymerization in the presence of polyelectrolytes. Poly-(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) was taken as a model polyelectrolyte due to the ease of varying its molecular weight during polymerization of the monomer. Depending on the polyacid molecular weight, crucial changes in the shape of charge– and potential–time dependences and cyclic voltammograms have been observed during potentiostatic, galvanostatic, and cyclic voltammetry syntheses of PANI, respectively. The results are considered in terms of the influence of molecular weight on proton condensation ability of the polyacid and, therefore, on the degree of aniline protonation and its local concentration in the vicinity of polyacid macromolecule. The PANI films obtained are characterized by cyclic voltammetry and UV–vis and Raman spectroelectrochemistry, and the influence of the polyacid molecular weight on these properties is discussed.

Two techniques of manufacturing a nanocomposite based on a complex of polyaniline with polymer acid and graphene are proposed. The electric conductivity of thin nanocomposite layers is higher than that of a polymer complex of polyaniline and strongly depends on the degree of oxidation of graphene. An explanation of the effect is suggested that takes into account electron interactions between the graphene planes and polyaniline backbone, as well as the possibility of formation of hydrogen bonds between functional groups of semioxidized graphene and polyacid. The results of surface topography analysis for thin layers of polyaniline and nanocomposite agree well with the regularities of the structure of each layer that are due to the above interactions between graphene and the polymer complex.

Liquid-crystalline state of dyes can be easy distinguished from the crystalline one by the appearance of characteristic long-wavelength optical absorption, the so-called J-band. Similarly, long-wavelength absorption of polyaniline is assumed to be the signature of its J-like liquid-crystalline state. When water evaporates from polyaniline adsorbed on a glass support during polymerization, the long-wavelength maximum at about 800 nm disappears, and one at 570 nm appears, characteristic for highly crystalline and strongly oriented thin film. Reversible red shift of long-wavelength absorption upon water adsorption is a significant feature of these films. By analogy with dyes, it is attributed to water-promoted superficial formation of J-like mesophase. Such surprising properties of wet films as propagation of chemical reduction and enhanced exciton transport, reported by us recently, can also be considered as a signature of the J-like liquid-crystalline state of polyaniline.

The template polymerization of aniline in the presence of polymeric sulfonic acids of various structures and their mixtures is studied. In the latter case, the dominant effect of a polyacid on the kinetics of aniline polymerization and the electronic structure of the resulting polyaniline complex is observed. As shown by viscometry measurements and IR studies, the intermolecular interaction between polyacids in their mixtures that leads to a change in the conformation of a flexible-chain polyacid is responsible for the dominant effect of a rigid-chain polyacid. The spectral and electrical properties of polyaniline-based interpolymer complexes are examined.

The matrix polymerization of aniline in the presence of mixtures of rigid-chain and flexible-chain polymer sulfoacids was investigated in the work. The optical, electric, and spectroelectrochemical properties of the forming interpolymer complexes of polyaniline, as well as their morphology, were studied. The dominating influence of rigid-chain polyacid on the process of formation of the interpolymer complexes of polyaniline even in the case of application of the mixture with the prevailing content of the flexible-chain polyacid was detected. The nonadditive dependence character of the viscosity of the mixtures of polyacid solutions, the duration of the induction period of aniline polymerization, and the optical absorbance and conductivity of the obtained complexes of polyaniline relative to polyacid ratios in the mixture was shown. The presence of the intermolecular interaction in the mixtures of polymer sulfoacids was shown via viscometry method, which may be the reason for the nonadditivity of the observed phenomena.

Films of polyaniline (PANI) interpolymer complexes were electrodeposited from aqueous solutions of aniline containing: (1) poly-(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA, flexible-backbone), (2) poly-(p,p′-(2,2′-disulfoacid)-diphenylen-tere-phthalamid) (t-PASA, rigid-backbone), (3) mixtures of the former two polyacids in different ratios (6:1, 3:1, 1:1, 1:3, 1:6). The obtained polymer films were characterized by UV–vis–NIR spectroscopy, CV, spectroelectrochemical and AFM measurements. An abnormally intensive influence of the rigid-chain polyacid on the process of matrix electropolymerization of aniline in the presence of the polyacid mixtures was at first demonstrated. Spectroelectrochemical properties of the obtained PANI complexes with the mixtures of flexible-backbone and rigid-backbone polyacids in different ratios (up to 6:1) are very similar to those ones for the complex with rigid-backbone t-PASA. The films prepared in the presence of polyacid mixtures (up to 6:1) have high absorbance in the NIR region similarly to the complexes with rigid-backbone t-PASA.

Experiments show that the electric conductivity of a polyaniline (PANI) complex with polyacid increases upon the introduction of graphene. It is found for the first time that this effect strongly depends on the degree of graphene oxidation: the presence of unoxidized and half-oxidized graphene increases the electric conductivity of the PANI complex by a factor of 3 and 20, respectively. An explanation of this phenomenon is proposed that takes into account the electron interactions between graphene planes and PANI backbone and the formation of hydrogen bonds between the functional groups of half-oxidized graphene and polyacid.

Various polyaniline (PANI) interpolymer complexes with polyacids in the form of molecular solutions were synthesized by chemical oxidative polymerization of aniline in the presence of water-soluble poly-(2-acrylamido-2-methyl-1-propanesulfonic acid) (flexible backbone), poly-p,p′-(2,2′-disulfoacid)-diphenylene-terephthalamide (t-PASA, rigid backbone), and their mixtures in different ratios. The complexes were characterized by UV-Vis-near infrared spectroscopy in solutions; also, the films’ drop-casts from these solutions were investigated by cyclic voltammetry, spectroelectrochemical, direct current (DC) conductivity, and atomic force microscopy (AFM) measurements. It was shown that the nature of polyacid affects the shape of spectra and the dynamics of their changes. The character of spectral changes during the matrix synthesis of PANI in the presence of mixtures of the rigid-chain and flexible-chain matrixes and the study of spectral properties of the obtained PANI solutions demonstrates the existence of the rigid-matrix domination effect in the process of formation of PANI interpolymer complexes. Spectral properties of the obtained PANI complexes with the mixtures of flexible-chain and rigid-chain polyacids of different ratios (3:1, 1:1, 1:3, and 1:6) are very similar to those ones for the complex with rigid-chain t-PASA. At the same time, there is a correlation between the electrical conductivity and morphology of the films of PANI complexes and their composition, the conductivity passing through a minimum for the complexes with the polyacid mixtures (6:1, 3:1, and 1:1).

Polyaniline (PANI) was synthesized by chemical oxidation of aniline in the presence of mixtures of water-soluble poly(sulfonic acids) of different nature. Under these conditions, the use of polyacid templates leads to the formation of interpolymer complexes of PANI and polyacid mixtures. The obtained PANI complexes were characterized by UV, visible, near IR, and Fourier transform infrared spectroscopy. It was shown that the rigidity of the polyacid backbone and the composition of a polyacid mixture affect the electronic structure of PANI complexes and the duration of the induction period of aniline oxidation. Domination of the more rigid-backbone template in the synthesis of PANI complexes with mixtures of the rigid- and flexible-backbone polyacids was observed. According to the viscometry and FTIR spectroscopic data, the reason of the domination is the existence of the intermolecular interaction between the polyacids in the mixture. In this case, duration of the induction period of aniline oxidation was between these values for pure polyacids.