Optical Characterization and Computational Chemical Evaluation of Electronic Localized States in Polyolefin

Abstract

SUMMARYOptical absorption spectra and photoluminescence spectra were obtained for eight kinds of polyolefin sheet samples using photons in a range from visible to vacuum ultraviolet (UV). 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 UV 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 UV photons. Quantum chemical calculations were carried out using polyethylene models with and without an unsaturated carbonyl to verify the abovementioned 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 abovementioned assumption of the luminescence center and its decomposition. C⃝ 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 188(1): 1-8, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com).

Optical, Structural, and Dielectric Properties of Composites Based on Thermoplastic Polymers of the Polyolefin and Polyurethane Type and BaTiO3 Nanoparticles

“…However, one possible speculation of this result may be the material surface oxidation or the formation of extrinsic carbonyl groups at the TPO surface due to the recorded PL spectrum under normal conditions, namely in the presence of O 2 and water vapor. A strong PL was also observed in polyethylene and propylene [47,48] and the explanation was reported taking into account the susceptibility of O 2 in the air to the surface of these polymers. In turn, the broad PL band of BaTiO 3 in the visibly wide range has also been reported in the literature [49,50], and was attributed to the electron-hole recombination from the predominant TiO 6 clusters observed in the ordered crystalline structure of BaTiO 3 responsible for the weak PL band of the material [50].…”

Quantum chemistry computing for terahertz spectra of fatty acid ester

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