Triboelectric charging between metals and insulators is usually thought to involve electron transfer. Doping some polymers with a small amount of salt can significantly change their charging properties, even reversing the sign to which they charge upon contact with a given metal. We show by means of secondary-ion mass spectrometry that ions of the salt are transferred across the interface in contacts between a doped polymer and a metal. Specifically, we observe a transfer of bromine ions when polystyrene doped with a small amount of the salt cetylpyridinium bromide is contacted to an indium surface.
The mechanism of contact charging between an organic salt modified polymer surface and a dissimilar polymer surface has been studied in the form of a xerographic developer, which consists of toner particles and polymer-coated metal beads. The model toner was prepared by solution coating 0.15 wt % of a negative charge additive, cesium 3,5-di-tertbutylsalicylate, on the surface of 9 um (diameter) sytrene-butadiene toner particles. The tribocharge was generated at a relative humidity (RH) of ~20%, by tumbling the model toner with polymer-coated beads (~130 um in diameter). It was determined by the standard blow-off procedure inside a Faraday cage. The surfaces of the toner and the polymer-coated metal beads, before and after the blow-off experiments, were analyzed by time-of-flight secondary ion mass spectrometry (TOF SIMS) and X-ray photoelectron spectroscopy (XPS). Results show that the cation of the charge additive, Cs+, transfer preferentially from the surface of the toner to the surface of the polymer-coated metal beads. The transferred Cs+ distributes uniformly on the bead surface according to TOF SIMS imaging. The relative Cs+ density on the surface of the beads recovered from experiments where the toner charge varies systematically, either by the length of the contacting time or by the electron affinity of the polymeric surface coating, was determined by both TOF SIMS and XPS techniques. Linear relationships with good correlation coefficients are consistently obtained between the negative toner charge and the relative Cs+ density. The results indicate that the transfer of Cs+ from the toner to the polymer-coated metal beads correlates to not only the sign but also the magnitude of the toner charge. This observation, along with the lack of humidity effect on toner charging, leads us to conclude that the model toner studied in this work is charged predominantly by an ion-transfer mechanism.
An improvement of the performance of bottom‐contact organic thin‐film transistors is demonstrated by embedding and planarizing the source/drain electrodes in a gate dielectric. The electric contact with the pentacene active layer is superior to conventional electrode configurations because of the favorable growth of pentacene grains adjacent to the source/drain electrode edges: these can be seen in the figure.
The triboelectrification mechanism of xerographic toner has been studied using a model toner prepared by solution coating a negative charge control additive, cesium 3,5-di-t-butylsalicylate (0.15% by wt.), on the surface of 9 pm styrene-butadiene toner particles. The toner was electrified by tumbling the toner particles with metal carrier beads (-130 pm). The tribo generated was measured by the standard blow-off technique inside a Faraday cage. The surfaces of the toner and carrier particles, before and after blow-off, were examined by time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy. Results suggest that there is a preferential transfer of Cs+ ions from the surface of toner particles to the surface of carrier beads during electrification. An ion-transfer mechanism is proposed and discussed.
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