Oxygen is a persistent hindrance in free radical polymerizations. Phthalocyanines (Pc) have been shown to be an effective molecule to circumvent the presence of oxygen by the excitation of molecular oxygen (3Σ-g) to its singlet state (1Δg) via triplet-triplet energy transfer with Pc rendering its reaction with initiating and propagating radicals no longer energetically favorable. Red-light irradiation of Pc depletes the concentration of oxygen to a threshold level in which monomer reaction with radicals is competitive. We have shown that not only does the red-light irradiation of the Pc Q band lead to 3Σ-g to 1Δg conversion but also that the UV-irradiation of the metal-complexed Pc B (Soret) band results in polymerization. For the first time, a single molecule has been utilized as both a photosensitizer and a photoinitiator. Irradiation of the Q band at 635 nm and subsequent irradiation at 365 nm of the B band leads to shortened or nonexistent induction times, as well as faster rates of polymerization and final conversions comparable to commercial photoinitiators. By coupling UV-Vis and FT-NIR spectroscopy, we were able to determine the kinetic behavior of the polymerization of di(ethylene glycol) ethyl ether acrylate (DEGEEA) in real-time, including the conversion, rates of polymerization, and quantum yields of photodegradation. Different metal complexes were studied to determine effects on their ability to exhibit this dual-functionality, and a mechanism for this phenomenon is proposed.

Investigation of a dual-role, two-color photosensitive molecule for oxygen removal and radical generation

256th National Meeting (2018)

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