Properties of thin layers of electrically conductive polymer/MWCNT composites prepared by spray coating

Abstract Electrically conductive films of polymers with low content of multiwalled carbon nanotube (MWCNT) polymers were prepared by multilayer spray coating technology; these films are suitable for application such as electrodes or charge transport layers in sensor systems. Melt mixed polymer/MWCNT composites with varying MWCNT content were first prepared, where the polymer was one of polycarbonate (PC), polymethylmethacrylate (PMMA) or polyvinylidenfluoride (PVDF). For spray coating, these composites were then dissolved in suitable solvents (chloroform or dimethylformamide). To ensure good dispersion of MWCNTs, the solutions were sonicated for a few minutes. Spray coating was carried out on glass and polyethylene terephthalate substrates in a nitrogen-purged glove box. The electrical properties of the spray coated films were evaluated by conducting surface and volume resistivity measurements and by conductive atomic force microscopy. Additional properties – including roughness, thickness and optical transmittance – were studied. Composite films prepared with PC showed low surface resistivity values of 1.3 × 105 Ω/sq. at a MWCNT content of 4 wt%. PMMA-based composite films exhibited similar values at a MWCNT content of 3 wt%. The lowest surface resistivity value (6.4 × 104 Ω/sq.) and volume resistivity value (5.1 × 103 Ω cm) were attained for PVDF/MWCNT composites containing only 2 wt% of MWCNTs; these films also exhibited the lowest roughness values and largest optical transmittance compared to PC- and PMMA-based composites. Electrically conductive films with minimum MWCNT contents between 2 and 4 wt% and a thickness of few microns were successfully produced by the spray coating method, which enables large area coverage and multilayer coatings at a high throughput with low material waste.