A simple europium complex,Eu（TTA）3 AA（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）3 AA to prepare fluorescence composites.The neat Eu（TTA）3 AA 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）3 AA decreased over 70% when the polymerization time was over 25 min at 145 °C.The results also revealed that the polymerizated Eu（TTA）3 AA 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）3 AA 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）3 AA 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）3 AA/NBR in comparison to that of Eu（TTA）3 AA/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.
Polyvinylpyrrolidone/ethylene-propylene-diene terpolymer （PVP/EPDM） sheath/core fibers, with the incorporation of Eu（TTA）3Phen （TTA=2-thenoyltrifluoroacetone, Phen=1,10-phenanthroline） complex （Eu-complex） in EPDM, were prepared by coaxial electrospinning. The composite fibers were further vulcanized by peroxide. Scanning electron microscopy （SEM） observations showed that the composite fi- bers had an average diameter of about 200 nm and a smooth surface. The dispersion of Eu-complexes in the fibers was characterized by transmission electron microscopy （TEM）, energy-dispersive X-ray spectroscopy （EDS）, and X-ray diffraction （XRD）. The studies revealed that the Eu-complex was dispersed in the EPDM fibers in the form of molecular clusters and/or nanoparticles with a diameter smaller than 10 nm. Fluorescence spectra and Judd-Ofelt parameters analysis showed that the luminescent quantum efficiency of the composite fibers was greatly improved when the Eu-complex content was 15 wt.%, because the fine dispersion of Eu-complex in EPDM facilitated the increase of radiative transition rate of the composite fibers over that of the neat complex powder.
Eu（OA）3（TTA） （OA=cis-9-octadecenoic acid, TTA=4,4,4-trifluoro-l-（2-thienyl）-l,3-butanedione） complexes （Eu- com- plexes） containing the ligand OA with long molecular chains were synthesized. The Eu（OA）3（TTA） complexes and peroxide were added into nitrile-butadiene rubber （NBR） by mechanical shearing to get the uncured composites. The cured composites were ob- tained by vulcanizing the uncured composites at high temperature. The in-situ reaction including polymerization and grafting of Eu-complex took place at the curing process, which was verified by Fourier transform infrared spectroscopy （FTIR） and X-ray dif- fraction （XRD）. Scanning electron microscopy （SEM） and transmission electron microscopy （TEM） observations showed the fine dispersion of Eu（OA）3（TTA） complex （Eu-complex） in the cured composites compared with the uncured ones. Fluorescent spectra and Judd-Ofelt parameters analysis revealed that the fluorescent intensity increased approximate linearly with the content of Eu- complex increasing due to the in-situ reaction and long molecular chains of OA. The fluorescent lifetime of composites was longer than that of original Eu-complexes.
