Ionizing radiation induced degradation of poly (2-methoxy-5-(2 '-ethyl-hexyloxy)-1,4-phenylene vinylene) in solution

In this paper we investigate the causes of the chromatic alteration observed in chloroform solutions of poly (2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) after gamma ray irradiation. Structural and chemical changes were analyzed by gel permeation chromatography, fourier transform infrared spectroscopy, and proton nuclear magnetic resonance techniques and complemented by electronic structure calculations. The results indicate chlorine incorporation in the polymer structure and main chain scission after irradiation. Based on our findings we propose that the main mechanism for the blue-shifts, observed in the UV-Vis absorption spectra of MEH-PPV after irradiation, is the result of a radical attack on the polymer main chain. Gamma rays generate radicals, (center dot)Cl and (center dot)CHCl(2) from chloroform radiolysis that attack preferentially the vinyl double bonds of the polymer backbone, breaking the electronic conjugation and eventually the chain. Our results indicate that oxygen does not play a major role in the effect. Electronic spectra simulations were performed based on these assumptions reproducing the UV-Vis experimental results. (C) 2011 American Institute of Physics. [doi:10.1063/1.3644946]Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

(EN) IONIZING RADIATION DOSIMETER (FR) DOSIMÈTRE DE RAYONNEMENT IONISANT (PT) DOSÍMETRO DE RADIAÇÃO IONIZANTE

(EN)A description is given of the invention of an ionizing radiation dosimeter that comprises a sealed holder that houses an organometallic polymer formulation, poly[1,1'-bis(ethynyl)-4,4'-biphenyl(bis(tributyl­phosphine))Pt (II)] (Pt-DEBP), dissolved in a halogenated organic solvent in different concentrations, with measurement of the dose of ionizing radiation being calculated on the basis of the ratio of the relative amplitude of the emission band altered by the presence of a new emitter centre formed after irradiation. (FR)L'invention concerne un dosimètre de rayonnement ionisant comprenant un support fermé hermétiquement permettant de stocker une formulation de polymère organique métallique poly[1,10-bis(éthynyl)-4,4'-biphényl (bis(tributylphosphine))Pt-(ll)] (Pt-DEBP) dissous dans un solvant organique halogéné en différentes concentrations, la mesure de la dose de rayonnement ionisant étant calculée au moyen du rapport de l'amplitude relative de la bande d'émission modifiée par la présence d'un nouveau centre émetteur formé après irradiation. (PT)É descrita a invenção de um dosímetro de radiação ionizante que compreende um suporte lacrado que armazena uma formulação de polímero orgânico metálico poly[1,10-bis(ethynyl)-4,4'-biphenyl (bis(tributylphosphine))Pt-(ll)] (Pt-DEBP) dissolvido em solvente orgânico halogenado em diferentes concentrações, com a mensuração da dose de radiação ionizante calculada mediante a razão da amplitude relativa da banda de emissão alterada pela presença de um novo centro emissor formado após a irradiação

Poly [1,1'-bis(ethynyl)-4,4'-biphenyl(bis-tributylphosphine)Pt(II)] solutions used as low dose ionizing radiation dosimeter

In this work, the effect of gamma radiation on the optical properties of polymetallayne poly[1,1'-bis(ethynyl)-4,4'-biphenyl(bis-tributylphosphine)Pt(II) ] (Pt-DEBP) in chloroform solution is studied. The samples were irradiated at room temperature with doses from 0.01 Gy to 1 Gy using a 60Co gamma ray source. A new band at 420 nm is observed in the emission spectra, in superposition to the emission maximum at 398 nm, linearly dependent on dose. We propose to use the ratio of the emission amplitude bands as the dosimetric parameter. This method proved to be robust, accurate, and can be used as a dosimeter in medical applications. © 2013 AIP Publishing LLC

Poly [1,1'-bis(ethynyl)-4,4'-biphenyl(bis-tributylphosphine)Pt(II)] solutions used as low dose ionizing radiation dosimeter

In this work, the effect of gamma radiation on the optical properties of polymetallayne poly[1,1'-bis(ethynyl)-4,4'-biphenyl(bis-tributylphosphine)Pt(II)] (Pt-DEBP) in chloroform solution is studied. The samples were irradiated at room temperature with doses from 0.01 Gy to 1 Gy using a Co-60 gamma ray source. A new band at 420nm is observed in the emission spectra, in superposition to the emission maximum at 398 nm, linearly dependent on dose. We propose to use the ratio of the emission amplitude bands as the dosimetric parameter. This method proved to be robust, accurate, and can be used as a dosimeter in medical applications. (C) 2013 AIP Publishing LLC

Structural Changes of Conjugated Pt-Containing Polymetallaynes Exposed to Gamma Ray Radiation Doses

""The effect of 60Co gamma rays irradiation on the polymetallayne [−Pt(PBu3)–C≡C–C6H4–C6H4–C≡C−]n (Pt-DEBP) of defined chain length corresponding to 10 repeat units, has been studied in detail. The UV–vis absorption spectra of Pt-DEBP have been recorded in solution upon exposure of the polymetallayne at increasing radiation doses in the range up to 90 Gy, with special care to the features related to low doses. Complex modifications of the chemical structure of Pt-DEBP could be accessed through NMR, FTIR, GPC, and XPS characterizations, which support the attack of Cl and H radicals coming from the radiolysis of the solvent, CHCl3, to the triple C≡C bonds of the backbone, leading to the formation of chlorinated double and single C–C bonds, with a concomitant increase of the molecular weight due to a recombinant effect of oligomer fragments upon irradiation. The presence of vinyl and single chlorinated moieties has been sustained from the simulation of the UV–vis spectra based on theoretical calculations."

Optical behavior of conjugated pt-containing polymetallaynes exposed to gamma-ray radiation doses

The effect of 60Co γ irradiation on the absorption and emission spectra of the organometallic polymer [-Pt(PBu3) 2-C≡C-C6H4-C6H 4-C≡C-]n (Pt-DEBP) in chloroform and toluene solutions for dosimetry applications has been studied. The system Pt-DEBP/chloroform can be used for dosimetric applications in two different ways: (i) monitoring of absorption spectra changes for higher doses (higher than 1 Gy), and (ii) monitoring of emission spectra changes for low doses (below 1 Gy). The response of the polymer solution to γ ray doses has been interpreted with the aid of theoretical studies based on time dependent density functional theory (TD-DFT) calculations on the absorption bands of a model complex and of the possible fragments coming from the degradation of the polymer backbone. It has been proposed that the observed changes are promoted by the attack of radicals, from the radiolysis of the solvent, on the polymer triple bonds. © 2011 American Chemical Society