Thermal stability of refractive index of polymethylmethacrylate layers prepared under electrical field

Porphyrin migration and aggregation in a poly(methylmethacrylate) matrix

“…The activation energy was calculated as E a = 27.5 kcal mol −1 . This corresponds closely to the value of 26.6 ± 0.4 kcal mol −1 reported for the activation energy of the β‐relaxation process in pure PMMA . Thus, it seems that the diffusion of porphyrin in PMMA occurs due to a β‐relaxation process in the polymer, a process that is associated with the rotation of the PMMA methoxy‐carbonyl side group.…”

“…Figure 2 displays DSC plots of pure and doped PMMA before and after annealing. Prior to annealing, the T g of doped films was 60 C, which is much lower than the T g of 114 C reported for pure PMMA [19]. Following annealing, the T g rose to 91…”

“…After annealing for 4,320 min, the peak located at 447 nm completely disappears. These changes in the absorption spectra indicate porphyrin aggregation . Because the absorption maxima are blue shifted, it is likely that the aggregates formed were H‐aggregates.…”

“…The mutual coupling of porphyrin molecules or their interaction with host particles, such as fullerenes or carbon nanotubes, can lead to luminescence quenching [19]. Figure 3B shows the results of the luminescence measurements for both the pristine and annealed films.…”

“…Together with absorption, another important optical property of porphyrins is their strong luminescence at green/red wavelengths. The mutual coupling of porphyrin molecules or their interaction with host particles, such as fullerenes or carbon nanotubes, can lead to luminescence quenching . Figure B shows the results of the luminescence measurements for both the pristine and annealed films.…”