Pressure-Induced Enhancement of Room-Temperature Phosphorescence in Heavy Halogen-Containing Imide and Polyimide.

To investigate the correlation between the aggregated state and photoluminescence (PL) mechanism of dual fluorescent (FL) and phosphorescent (PH) polyimides (PIs), the photophysical processes of FL-type , PH-type , and their corresponding imide model compounds ( and ) dispersed in poly(methyl methacrylate) (PMMA) films were analyzed at elevated pressures up to 8 GPa using a diamond anvil cell. Dibromo-substituted demonstrated a shorter wavelength absorption than owing to the larger dihedral angle in the biphenyl moiety. Both MCs exhibited red-shifts in their absorption spectra with increasing pressure, indicating planarization occurred at the biphenyl moieties associated with the compression of the free volume in PMMA.