Investigation of Charge Stability in Amorphous Fluorinated Polymer Using Quantum Chemical Analysis

In the present study, charge trapping phenomenon in amorphous fluorinated polymer is investigated for development of a new electret material. Solid-state quantum chemical analysis is adopted to calculate electron affinity (EA) of CYTOP (Cyclic Transparent Optical Polymer) molecules. The calculation accounts single-molecular energy of charge trapping molecule, influence of surrounding molecules, and diversity of molecular geometry in the amorphous polymer systems. Calculated EA for CYTOP CTX-S is found to be in good agreement with the measured value with the low-energy inverse photoelectron spectroscopy. Thermally stimulated discharge (TSD) measurement is performed to evaluate stability of the trapped charges. For negatively-charged CYTOP polymers with different end groups, the order of peak temperature of the TSD spectra is in accordance with that of the calculated solid state EAs, indicating that the present method can properly predict the charge trapping performance of amorphous polymer electrets. It is also shown from the TSD spectra that the charge trapping mechanisms are different for negatively-/positively-charged CYTOP.