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In this work, we present a new class of materials with non-linear electrical behaviour: the Organic Polymeric Varistors. These devices were built using a conducting polymer, polyaniline, and a conventional low-cost dielectric polymer, acrylonitrile–butadiene–styrene copolymer. The apparatus has low-voltage varistor behaviour with a breakdown field of around 10 V, and a non-linear coefficient of 5.0. They also remain stable after several voltage–current cycles and its preparation procedure is easy and inexpensive.

The self-doping mechanism for charge transport is investigated in layer-by-layer (LBL) films from two conducting polymers, namely poly( o -methoxyaniline) (POMA) and poly(3-thiophene acetic acid) (PTAA). The efficiency of charge intercalation, defined as the ratio between the charge and the mass change, is twice for the POMA/PTAA LBL film in comparison with a cast POMA film. This is attributed to differences in the diffusion-controlled charge and mass transport, where distinct ionic species participate in the LBL films, as demonstrated with experiments using a quartz crystal microbalance. The doping efficiency for LBL film is the same, i.e., 3.93 × 10 −4 and 3.56 × 10 −4 g/C for the Li + and (C 2 H 5 ) 4 N + doped films, and is different for the cast POMA film, i.e., 11.3 × 10 −4 for Li + and 6.45 × 10 −4 g/C for (C 2 H 5 ) 4 N + . Therefore, once no significant differences in the intercalation mechanism are observed when different cations, Li + or (C 2 H 5 ) 4 N + , are used with the LBL films, this indicates that the self-doping mechanism is controlled by the exchange of anions.

Photoluminescence (PL) of polymeric blends with poly(vinyl alcohol) (PVA) and poly(3-thiopheneacetic acid) (PTAA) was investigated. We found an increase in the PL intensity induced by laser irradiation. The PL quantum efficiency was dependent on irradiation time, laser intensity, and PTAA doping state (acid or salt). PL intensity increased up to 200% for acid PTAA and 50% for salt PTAA. The PL efficiency relative enhancement was 314% for acid PTAA and 140% for salt PTAA. Using infrared spectroscopy, we related this effect to hydrogen bond interaction between PTAA and PVA excited states induced by laser irradiation that reduced the non-radiative decay rate.

Stable aqueous solutions of poly(3-thiopheneacetic acid) (PTAA), including its acid form, were suitably prepared by using poly(vinyl alcohol) (PVA) as steric stabilizer surfactant. The optical properties of PTAA were investigated in aqueous solution of PVA, water and different alcohols. Both absorption and emission measurements revealed that the optical behavior of PTAA is pH-dependent. The maximum of absorption of PTAA salt in PVA solution shifts from 480 to 415 nm when acid conditions are established, producing a color change from brown-red to yellow. The same solvatochromic effect was also verified from the emission spectra, being the band shift attributed to conformational changes of the PTAA structure due to formation or dissociation of hydrogen bonds between carboxyl groups of PTAA and hydroxyl groups of PVA. In a similar way, the impact of solvents such as water, ethanol and ethylene glycol was also studied on both absorption and emission spectra of PTAA.

In this study, conducting blends of poly(acrylonitrile-butadiene-styrene) and polyaniline doped with dodecylbenzene sulfonic acid were prepared by solution blending. In order to understand the electrical conduction mechanism of the samples, DC electrical conductivity measurements of the blends were carried out in the temperature range of 80–320 K. The experimental results fit well with Mott's model of three-dimensional variable range hopping conduction. The values of Mott's temperature, density of states at the Fermi energy, average hopping distance and barrier height for the composites were calculated and presented.

A systematic investigation of the redox properties of polyaniline in aqueous solutions using the capacitance–potential curves was done. The variation of the capacitance values in different regions of the sweep potentials was associated with the charge transport and the capacitive processes in the polymeric film. An increase in the capacitance was observed in the region of the first redox process (0.1 to 0.6 V), which is associated with the charge accumulation in the film due to the polymer oxidation and the Cl − intercalation. In the third redox process in the voltammograms (0.85 to 1.2 V), a decrease in capacitance was observed which could be related to the H + deintercalation and the formation of the pernigraniline state.

Cyclic voltammograms and capacitance-potential curves were used to investigate the redox process of poly(3-methylthiophene) films. During the reduction and oxidation of these films the charge transfer and mass transport phenomena are distinguished by the simultaneous analysis of cyclic voltammograms and capacitance data.

Multilayer self-assembled (SA) films from poly(3-thiopheneacetic acid) (PTAA) and poly(o-methoxyaniline) (POMA) have been deposited on ITO substrates. The UV-Vis. absorption increased almost linearly with the number of layers. The cyclic voltammetry (CV) results pointed to a different behavior from either POMA or PTAA electrochemical response, probably because of a charge transfer interaction between the carboxyl groups of PTAA and the POMA chains.

Electron Spin Resonance (ESR) data in pressed pellets of doped poly(3-methylthiophene) (P3MT) show a single ESR line that changes into a broad and a narrow superimposed lines below 225K. D.C. susceptibility measurements using a SQUID susceptometer didn't reveal any special feature at this temperature. Assuming crystallization of the polymer, we attribute the broad line to the crystalline fraction of the polymer and the narrow line to the amorphous one.