Accelerated ultraviolet aging of structural and luminescent properties of the ureasil-polyether hybrid materials U-PEO:Eu3+ and U-PPO:Eu3+

POLYMER

卷:177

Article

Palacio, Gustavo^1,2  Boyer, Damien²  Therias, Sandrine²  Pulcinelli, Sandra H.¹  Mahiou, Rachid²  Chadeyron, Genevieve²  Santilli, Celso, V¹ 

[1] Sao Paulo State Univ UNESP, Chem Inst, BR-14800060 Araraquara, SP, Brazil

[2] Univ Clermont Auvergne, CNRS, SIGMA Clermont, Inst Chim Clermont Ferrand, F-63000 Clermont Ferrand, France

关键词: Organic-inorganic hybrid materials;    Polyether;    Sol-gel;    Photooxidation;    Photoluminescence;   

DOI  :  10.1016/j.polymer.2019.05.060

来源: Elsevier

【 摘 要 】

In this paper, we evaluate the role played by the polyether type and chain length on the complexation of Eu3+ by the urea group of siloxane-polyether organic-inorganic hybrid materials based on polyethylene oxide (U-PEO, mw = 1900 g mol(-1)) and polypropylene oxide (U-PPO, mw = 230, 2000, and 4000 g mol(-1)). Investigation was made of the effect of the photooxidation of the PEO and PPO chains, induced by artificially accelerated ultraviolet aging (lambda >= 300 nm), with the decomplexation of Eu3+ from the urea-polyether array. Fourier transform infrared (FTIR) and photoluminescence (PL) spectra evidenced loss of the ligand-to-metal charge transfer (LMCT) when the Eu-3(+) cations were unable to disrupt the strong hydrogen-bonded urea/urea aggregates formed using shorter U-PPO chains (230 g mol(-1)) or semicrystalline U-PEO (1900 g mol(-1)). FTIR analysis showed that formate was the main photoproduct formed continuously during the artificial ultraviolet aging of U-PEO (1900 g mol(-1)) and U-PPO (2000 g mol(-1)), with concomitant decreases of Eu3+ complexed to urea bridges, spatially correlated siloxane nodes, and the Judd-Ofelt parameter Omega(2) (R). The kinetics of all these parameters were described by exponential laws with comparable time constants, evidencing the sensitivity of the Eu3+ photoluminescence to the elimination/formation of the hydrogen-bonded urea-polyether array during the photooxidation of PPO chains. In the case of U-PEO:Eu3+, different time constant values were observed, indicating the existence of a faster process governed by the facilitated transport of the oxidative species through the amorphous moieties of the semicrystalline U-PEO. This sensitivity of structural and PL properties arising from the photo-induced degradation of ureasil-polyether films can be exploited in the fabrication of new transparent, flexible, and biocompatible UV dosimeters and sensors.

【 授权许可】

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