Photochromism and luminescence of dopant chromophores through two-photon ionization in polymer films

Two-photon ionization and recombination processes of an aromatic chromophore doped in polymer films were studied and the features of these processes were discussed in relation to photofunctional polymers. An aromatic molecule having low ionization potential, e.g., N,N,N prime ,N prime N-letramethyl-p-phenylene diamine doped in poly(methyl methacrylate) (PMMA) film was easily photoionized by intense laser light excitation, giving a colored radical cation (photochromism) and a trapped electron in PMMA matrix. As a reversed process, the radical cation recombined with the trapped electron, showing discoloration and emitting luminescence, either isothermal luminescence (ITL), or thermoluminescence (TL). In this report, ITL and TL through the charge recombination process were studied and the luminescence was suggested as a mean of the read-out of photorecording.