Wavelength-selected radiothermoluminescence of polyethylene doped with pyrene

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The influence of temperature (77-230 K) on the fate of pyrene (Py) radical ions and Py excited states in irradiated poly(dimethylsiloxane) (PDMS) doped with Py is described. At 77 K, the Py radical ions seem to be stable, whereas the Py excited states [fluorescence ( ϭ 395 nm) and phosphorescence ( ϭ 575-650 nm)] are generated via tunneling charge transfer. In the range of the glass-transition temperature (T g ϭ 152-153 K), the Py radical ions start to decay, taking part in a recombination process and leading to the Py monomer and Py excimer fluorescence ( ϭ 475 nm). The wavelength-selected radiothermoluminescence (WS RTL) observed at approximately 395, 475, and 600 nm has helped us to identify the T g range (152-153 K). The absorption maximum at approximately 404 nm, found in the temperature range under consideration, is thought to represent PyH • , cyclohexadienyl-type radicals produced as a result of the reaction of Py •Ϫ with protonated PDMS macromolecules. With the initial-rise method of evaluating the activation energy (E a ) with the WS RTL peaks observed in the T g range, E a values of 123-151 kJ mol Ϫ1 have been found. Such high E a values can be explained by the contribution of energy connected to the molecular relaxation of the matrix in the T g range. The well-known Williams-Landel-Ferry equation, with universal constants C 1 ϭ 17.4 and C 2 ϭ 12.7, has been successfully applied to the interpretation of old pulse-radiolysis/viscosity data found for crosslinked PDMS doped with Py. The mechanisms involved in these phenomena are discussed.

Section: Resultssupporting

confidence: 81%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ionic and excited species in irradiated poly(dimethylsiloxane) doped with pyrene

Szadkowska–Nicze

Mayer

2004

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Long‐lived species generated via irradiation of poly(methyl methacrylate) containing pyrene

Szadkowska–Nicze¹,

Mayer²

2001

The fate of long‐lived species [pyrene (Py) radical cations and Py–cyclohexadienyl‐type radicals] generated by electron‐beam irradiation at room temperature in poly(methyl methacrylate) (PMMA) doped with Py is described. The separation of reacting solute intermediates and the relaxation phenomena seem to be the main factors limiting the reactivity of long‐lived Py species in the PMMA matrix. The temperature‐stimulated recombination of ionic species in PMMA doped with Py results in Py excited‐state formation. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4110–4118, 2001

Synthesis and photophysical properties of polyethylene containing pyrenyl units in the side chain

Naga¹,

Tano²,

Tomoda³

2012

Copolymerization of ethylene and diallyl-bis(pyren-1-yl)-silane (APyS) was investigated with zirconocene catalysts, rac-ethylenebis(indenyl)zirconium dichloride (1) and diphenylmethylene(cyclopentadienyl)(9-fluorenyl)zirconium dichloride (2), using methylaluminoxane as a cocatalyst. APyS was copolymerized via both 1,2-insertion and cyclization insertion, and cyclization selectivity, ratio of cyclized insertion unit, of APyS in the copolymers obtained with Catalyst 1 was higher than that obtained with Catalyst 2. Catalyst 2 showed a higher reactivity for APyS than Catalyst 1. Photophysical properties of the copolymer were investigated by UV-vis and photoluminescence (PL) spectroscopy, and absorption and fluorescence derived from pyrenyl groups were detected in the copolymers.Chloroform solution of the copolymer showed emission derived from both monomer and eximer of pyrenyl units. Only the emission derived from eximer of pyrenyl units was observed in the cast film. The polarized PL spectrum of an oriented film showed anisotropy, and the polarization excitation parallel to the drawing direction showed high fluorescence intensity. V C 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: [4223][4224][4225][4226][4227][4228][4229] 2012