Abstract
In this work, we present the method for the creation of an anisotropic electric pattern on thin poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) films through PSS grafting by azo-containing moieties followed by light-induced polymers redistribution. Thin PEDOT:PSS films were deposited on the flexible and biodegradable polylactic acid (PLLA) substrates. The light-sensitive azo-groups were grafted to PSS using the diazonium chemistry followed by annealing in methanol. Local illumination of azo-grafted PEDOT:PSS films through the lithographic mask led to the conversion of azo-moieties in Z-configuration and further creation of the lateral gradient of azo-isomers along the film surface. The concentration gradient led to the migration of PSS away from the illuminated area, increasing the PEDOT chains’ concentration and the corresponding increase of local electrical conductivity in the illuminated place. Utilization of mask with linear pattern results in the appearance of conductive PEDOT-rich and non-conductive PSS-rich lines on the film surface, and final, lateral anisotropy of electric properties. Our work gives an optical lithography-based alternative to common methods for the creation of anisotropic electric properties, based on the spatial confinement of conductive polymer structures or their mechanical strains.
Highlights
Conductive polymer (CP) composites are receiving a great deal of attention owing to their unique electrical, mechanical, and processing properties [1,2]
We extended the above-mentioned approach on the preparation of the PEDOT:PSS film with anisotropy in a surface electrical conductivity by a simple and scalable procedure
PEDOT:PSS aqueous solution was deposited by spin coating at 500 rpm for 10 min on polylactic acid (PLLA) films’ surfaces and thermally annealed for 5 h at 40 ◦ C under an argon atmosphere
Summary
Conductive polymer (CP) composites are receiving a great deal of attention owing to their unique electrical, mechanical, and processing properties [1,2]. The anisotropic conductivity can arise from the geometrical arrangement of conductive pathways in CPs composites or from the mobility anisotropy of charge carriers in the intrinsically conjugated polymers [15,16,17] In the latter case, the anisotropy appears as a result of the ordered alignment of polymers chains or crystal domains [18,19]. An alternative method for the introduction of anisotropic conductivity to CPs lies in the patterning of their thin films [28] Using this approach, significant resistance anisotropy, larger than four orders of magnitude, was obtained [29]. For introduction of anisotropic conductivity we used the light, which makes this the first report of the application of such stimuli in the case of CPs (light was previously used for creation of anisotropic properties in the case of liquid crystal [39,40] but was never reported for realization of such a goal in the CP field)
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