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Mechanistic studies on the photodegradation of 2,5-dialkyloxyl-substituted para-phenylenevinylene oligomers by singlet oxygen

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Abstract

Time-dependent UV/visible absorption changes are observed on photolysis of aerated solutions of monodisperse, vinyl end-capped 2,5-diheptyloxyl substituted PV-oligomers (OPV, n = 1, 2, 3). In all cases, photolysis occurs in at least two distinct stages. Evidence for the intermediacy of singlet oxygen comes from pulse radiolysis and time-resolved luminescence studies, which confirm formation of the OPV triplet state and its quenching by molecular oxygen to produce singlet oxygen. The subsequent reaction with oligomers is observed directly by time-resolved phosphorescence and indirectly through product identification. The results strongly suggest that the reaction between singlet oxygen and OPV proceeds viacycloaddition, leading to bond scission and aldehyde group formation. The reactivity of vinylene linkages is greater than of vinyl end groups. Consequently, the photostability decreases as the chain length is extended. Implications on the oxidative degradation of poly(p-phenylenevinylene)s in optoelectronic devices, and of competing singlet oxygen and superoxideradical aniondegradation pathways, are discussed.

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Author notes

  1. Oliver Narwark

    Present address: Schreiner Group GmbH & Co. KG, Oberschleissheim, Germany

  2. Ralf Peetz

    Present address: CUNY/College of Staten Island and Graduate Center Doctoral Faculty, Department of Chemistry and Center for Engineered Polymeric Materials, 2800 Victory Boulevard, Staten Island, NY, 10314, USA

Authors and Affiliations

  1. Departamento de Química, Universidade de Coimbra, 304-535, Coimbra, Portugal

    Hugh D. Burrows

  2. Institut für Technische und Makromolekulare Chemie, Universität Hamburg, 20146, Hamburg, Germany

    Oliver Narwark, Ralf Peetz & Emma Thorn-Csányi

  3. Organic Electroactive Materials Research Group, Department of Physics, Durham University, Durham, UK, DH1 3LE

    Andrew P. Monkman

  4. Department of Radiochemical Targeting and Imaging, P.I.C.R., Christie Hospital NHS Trust, Manchester, UK, M20 9BX

    Ian Hamblett

  5. Biosciences Research Institute, University of Salford, UK, M4 4WT

    Suppiah Navaratnam

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Correspondence to Hugh D. Burrows.

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† This article is published as part of a themed issue in appreciation of the many important contributions made to the field of molecular photophysics by Jan Verhoeven.

‡ Electronic supplementary information (ESI) available: Decay of transient absorption of DHepODVB-dimer triplet state at 500 nm in argon saturated and aerated solutions; mass spectrum of the photolysis product 2,5-diheptyloxy-terephthalaldehyde. See DOI: 10.1039/c0pp00053a

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Burrows, H.D., Narwark, O., Peetz, R. et al. Mechanistic studies on the photodegradation of 2,5-dialkyloxyl-substituted para-phenylenevinylene oligomers by singlet oxygen. Photochem Photobiol Sci 9, 942–948 (2010). https://doi.org/10.1039/c0pp00053a

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