Pavol Fedorko

Insulator-Metal transition in Polyaniline induced by plasticizers

We show for the first time that the addition of classical plasticizers. such as triphenyl or tritolyl phosphate, to solution processed polyaniline (PANI) films leads to dramatic changes in their transport properties, despite the fact that both admixtures are incapable to interact with PANI via any type of doping. In particular, a veritable plasticizer induced Insulator-Metal transition takes place, as revealed by the change of the sign of the temperature coefficicnt of the reduced activation energy W. Since X-Ray diffraction studies indicate that the plasticizers do not enter into the crystalline parts of the polymer, hut only modify its amorphous halo. the obtained results are consistent with the inhomogeneous disorder model.

Polyamide grafted with polypyrrole: formation, properties, and stability

Conducting textiles of polyamide (PA) fabrics and polypyrrole (PPy) were prepared by in situ oxidative chemical polymerisation of pyrrole (Py) on the surface of PA textiles using FeCl3 as oxidant. The anionic surfactant, dodecylbenzenesulphonic acid, was used as co-dopant during Py polymerisation on the textile surface. The influence of the monomer amount and polymerisation conditions on formation of the conducting PPy layer, conductivity, morphology, and stability of the prepared PA/PPy was studied. The conductivity of modified textiles decreased rapidly after the washing process, so a special Py-functionalised silane (1-(3-(triethoxysilyl)propylamino)-3-(1-H-pyrrole-1-yl)propan-2-ol; SP) was synthesised and applied to the PA surface prior to PPy formation. The presence of SP on the PA surface after completion of the sol-gel process was verified by Fourier transform infrared spectroscopy with an attenuated total reflectance. Pyrrole polymerisation was subsequently applied to the SP pre-treated textile surface. The influence of SP concentration on both the fastness of the conducting layer after the washing process and stability of the electrical conductivity of the prepared PA/PPy samples was investigated. Surface conductivity of the samples treated and untreated by the sol-gel process of SP was measured both prior to and after washing of the prepared textiles. It was found that an application of 0.6 mass % of SP significantly improved the fastness of the PPy layers. Examination of the modified PA surface using scanning electron microscopy disclosed the differences in the formation of PPy on PA textiles when using SP and also showed differences on the PPy modified textile surface prior to and after washing. The method of X-ray photoelectron spectroscopy was used for a detailed study of the surface composition. It was confirmed that the pre-treatment with Py-functionalised triethoxysilane significantly influenced the chemical composition of the PA surface modified with PPy.

New counterion-plasticized polyaniline with improved mechanical and thermal properties : comparison with PANI-CSA

Electrical and mechanical properties, as well as conductivity evolution under thermal ageing were investigated in a newly developed polyaniline system based on a new multifunctional dopant, di(2-ethylhexyl) ester of 4-sulfophthalic acid. From comparison with PANI-CSA, it appears that mechanical properties and thermal stability are considerably improved while metallic-like conductivity is preserved.