|Erhard, D.P.; Giesa, R.; Altstädt, V.; Schmidt, H.-W.: Synthesis and Structure-Property Relationships of Fluorinated Poly(ether imide)s as Electret Materials, Macromolecular Chemistry and Physics, 208(14), 1522-1529 (2007) -- DOI: 10.1002/macp.200700111|
The aim of this work was to establish and better understand the structure-property relationship of fluorinated aromatic poly(ether imide)s (PEI) with respect to their electret performance. Therefore two series of PEIs with increasing fluorine content were synthesized. All PEIs are amorphous materials with glass transition temperatures above 220 °C. Thin films with thicknesses around 100 µm were compression molded and corona charged, and isothermal surface potential decay was investigated at 90 °C as an accelerated test for the electret performance. In comparison to the corresponding non-fluorinated PEI, an improvement of up to thirty-fold was achieved by the incorporation of trifluoromethyl moieties. Out of the investigated fluorinated PEIs, the polymer with the best charge storage performance maintained 87% of the initial surface potential charge after annealing at 90 °C for 24 h. It was also found that, within the investigated series, the highest fluorine content does not necessarily result in the best charge-storage properties.