Optical characterization and computational chemical evaluation of electronic localized states in polyolefin

Tomoyuki Arai, Masashi Hosobuchi, Norikazu Fuse, Kyozaburo Takeda, Yoshimichi Ohki

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    Abstract

    Optical absorption spectra and photoluminescence spectra were obtained for eight kinds of polyolefin sheet samples using photons in a range from visible to vacuum ultraviolet. Almost all samples were found to exhibit an absorption peak at around 6.5 eV and a luminescence band at around 4.3 eV. The luminescence was found to be induced by the absorption. Furthermore, it was found that successive absorption of ultraviolet photons weakened the luminescence intensity. It is assumed from these results that α ,β -unsaturated carbonyls are luminous and that the carbonyls are decomposed through the Norrish type II reaction by absorbing ultraviolet photons. Quantum chemical calculations were carried out using polyethylene models with and without an unsaturated carbonyl to verify the above-mentioned assumption. As a result, the model with an unsaturated carbonyl was found to have localized electronic states in the forbidden band. One of the differential energies between the states is close to the photon energy, by which the luminescence is induced. The bond length of a double bond, which is next to the carbonyl, was found to be longer at the excited singlet state than at the ground state. These results obtained by computation support the above-mentioned assumption of the luminescence center and its decomposition.

    Original languageEnglish
    Pages (from-to)760-766
    Number of pages7
    JournalIEEJ Transactions on Fundamentals and Materials
    Volume132
    Issue number9
    DOIs
    Publication statusPublished - 2012

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    Keywords

    • Computational chemistry
    • Optical absorption
    • Photoluminescence
    • Polyolefin
    • Quantum chemical calculation

    ASJC Scopus subject areas

    • Electrical and Electronic Engineering

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