Irreversible photodegradation is usually undesirable in many applications of doped polymers that require exposure to light. A wide variety of organic molecules doped in polymers, when allowed to stay in the dark after photodegradation, have been continuously observed to recover in hours to days without any treatment using various optical characterization techniques. Both 1-Aminoanthraquinone (1AAQ) and 1-Amino-2-methylanthraquinone (1,2-AMAQ), also known as disperse orange 11 (DO11), doped in poly(methyl methacrylate) (PMMA) have been found to exhibit a good propensity for recovery from photodamage. We have computed UV-Vis absorption spectra of possible photodegraded DO11 species using time-dependent density functional theory, and studied the recovery process of 1AAQ/PMMA and DO11/PMMA after irradiation with a 532 nm wavelength cw pump laser using linear absorption spectroscopy and amplified spontaneous emission (ASE) techniques. In addition, Fourier transform infrared spectroscopy was used as a probe of degradation products from 1AAQ/PMMA . Photochemical reaction between dye and thermally degraded polymer caused by energy transfer from excited dye to the polymer is proposed to be responsible for photodegradation of 1-substituted aminoanthraquinones doped in PMMA matrices, and the unstable product (damaged dye) can gradually recover to the original dye or decompose to irreversibly damaged products resulting in only partial recovery from photodegradation. The proposed mechanism is supported by all observations in our study and can potentially be applied to many systems exhibiting reversible photodegradation. This study posits that photoinduced thermal degradation of a polymer host is responsible for photodegradation of the dopants, therefore should be taken into account in designing dye-doped polymers to improve the stability and extend the lifetime of devices using such materials.

Mechanism for reversible photodegradation of 1-substituted aminoanthraquinones doped in poly(methyl methacrylate)

249th National Meeting (2015)

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