279468 Contact De-Electrification of Charged Polymers

Wednesday, October 31, 2012: 5:05 PM
Butler West (Westin )
Siowling Soh, Chemistry and Chemical Biology, Harvard University, Cambridge, MA and George M. Whitesides, Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA

Despite 2500 years of studying contact electrification of insulating materials, the mechanisms involved in charge transfer between the materials are still not well understood. Studies in this field have remained largely empirical, involving nonlinear dependence in contact charging with external factors (e.g. humidity) and sometimes in inconsistencies among different studies (e.g. the ordering of materials in the triboelectric series). These studies suggest that contact electrification is likely due to a combination of several important mechanisms, such as electron, ion and material transfer. Here, we describe another mechanism involved in the process of contact electrification: polymeric objects charged with the same polarity, discharge upon contact. This phenomenon – which we refer to as “contact de-electrification” – is unexpected, with charges presumably transferred elsewhere in order for the law of charge conservation to hold. We show that contact de-electrification occurs for all the different polymers studied; moreover, charges got transferred from the polymeric objects to the gaseous atmosphere and not elsewhere, for example, any solid substrate. These results show that contact de-electrification is an important consequence of contact electrification, in addition to other widely discussed mechanisms, such as material transfer. We further demonstrate the relevance of contact de-electrification in interacting particles (e.g. granular flows in industrial processes and dust storms/explosions) by constructing a “model system” comprising multiple interacting polymeric beads.

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See more of this Session: Structure and Properties in Polymers II
See more of this Group/Topical: Materials Engineering and Sciences Division