Variations in Aggregation Structures and Fluorescence Properties of a Semialiphatic Fluorinated Polyimide Induced by Very High Pressure

Abstract

Variations in the molecular aggregation structures and optical properties of a semialiphatic fluorinated 10FEDA/ DCHM (poly(4,4′-diaminocyclohexylmethane 1,4-bis(3,4-dicarboxytrifluorophenoxy) tetrafluorobenzeneimide) polyimide (PI), which exhibits strong cyan fluorescence, were examined under very high pressure up to 8 GPa using synchrotron wide-angle X-ray diffraction (WAXD) and fluorescence spectroscopy. The fluorescence intensity of a PI film imidized at 220 °C was significantly reduced by applying pressure up to 1 GPa, which should be due to an appreciable reduction in interchain free volume, as indicated by a decrease in the d-spacing values of WAXD peaks which correspond to intermolecular ordering. In contrast, a PI film imidized at 300 °C, which exhibited weaker fluorescence than that imidized at 220 °C at atmospheric pressure, demonstrated a much smaller reduction in fluorescence intensity below 1 GPa. Such differences in pressure dependence clearly reflect the degrees of PI chain packing formed at different imidization temperatures. These phenomena induced by high pressure were almost reversible between pre-and postpressurization states with small hysteresis in the WAXD patterns and fluorescence spectra.

Pressure Induced Variations in Refractive Index of Aromatic Polyimide Film Analyzed by Brillouin Scattering

“…For stimulating and perturbing the aggregation structures of polymer chains in the solid state, application of high pressure is an effective way because it can directly reduce the intermolecular free volume included in polymer solids. The effects of pressurization on the aggregation structures, optical, and physical properties of PIs have been widely investigated by spectroscopic techniques and X-ray scattering methods under high pressure [14][15][16][17][18][19]. Recently, we have reported the relationship between the optical properties and the aggregation structures of PI films by UV/vis/IR absorption, fluorescence spectra, and synchrotron WAXD patterns measurement under high pressure up to 8 GPa [15][16][17][18][19].…”

Dielectric Spectroscopy of Polyimide Films Treated by Nanosecond High Voltage Pulsed Driven Electrical Discharges in Water

“…Two broad peaks were identified at ca. 16 and 27°2θ, corresponding to d‐spacings around 5–6 Å and 3.6–3.8 Å, which are usually attributed to intermolecular ordering, i.e., interchain packing and π‐stacking of the polymeric chains, respectively . Calculated d‐spacings are shown in Table .…”

Effective Reduction of Volumetric Thermal Expansion of Aromatic Polyimide Films by Incorporating Interchain Crosslinking

“…As described above, this indicates that curing at 330 • C promoted the formation of ordered structures accompanied by the reorientation of PI chains, whereas curing at >330 • C accelerates the reorientation of the PI chains in the ordered structures during thermo-crosslinking. In contrast, the WAXS patterns of the MPD-PI films, as shown in Figure 6b, showed only broad scatterings without any apparent peaks, indicating that the amorphous nature formed after imidization was maintained even after thermal-crosslinking at >330 • C. The gradual displacement of the broad peak at approximately 10 nm −1 to larger q values reflects the interchain distance shortening caused by the crosslinking reactions [20]. …”