Self-polymerization of Eu(TTA)3AA in rubber and their fluorescence effect

A simple europium complex, Eu(TTA)3AA (TTA=4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione, AA=acrylic acid) was synthesized by a simple solution method. Then, two kinds of rubber matrix, nitrile-butadiene rubber (NBR) and silicone rubber (SiR) were used as the substrate for Eu(TTA)3AA to prepare fluorescence composites. The neat Eu(TTA)3AA complex showed the ability of self-polymerization when it was heated at 145 °C. It was found that the fluorescence intensity of the neat Eu(TTA)3AA decreased over 70% when the polymerization time was over 25 min at 145 °C. The results also revealed that the polymerizated Eu(TTA)3AA could be dispersed in nano-scale in two matrices and the luminescent intensities decreased 52% in NBR matrix, and 95% in SiR matrix compared with two relative compounds without crosslinking. To optimize the luminescence intensity of the composites, the Eu(TTA)3AA polymerization kinetic process in matrix was investigated in detail by controlling the temperature, the crosslinking agent, etc. The results showed that the peroxide could accelerate Eu(TTA)3AA self-polymerization in the rubber matrix, and therefore improved the dispersion, but not be helpful for the luminescence intensity enhancement. In addition, the relatively higher luminescence intensity in Eu(TTA)3AA/NBR in comparison to that of Eu(TTA)3AA/SiR might contribute to the interaction between nitrile group (–CN) in NBR and Eu-complexes, suggesting that the luminescence intensity of the composites also depended on the matrix characteristics.