Optical and structural characteristics of PMMA films doped with a new anisometric Eu^III complex

Abstract

A new film material capable of transforming UV radiation into visible light was obtained from a highly anisometric Eu III complex with organic ligands in a polymethylmethacrylate (PMMA) matrix and then structurally characterized. An important advantage of the synthesized complex is its good solubility in organic solvents such as dichloromethane, chloroform, THF, toluene, etc. The ligand environment (flexible alkyl and cyclohexyl substituents) of the Eu III complex was selected to prevent crystallization, to inhibit the formation of defects in the structure of films and to provide its uniform distribution in the polymer during polymerization. As a result we obtain an Eu III complex of the film with remarkable thermal behavior: the complex melts to isotropic liquid without decomposition, it supercools at ambient temperature and it forms a stable amorphous material at low (up to À30 C) temperatures. The films were prepared by two methods: bulk polymerization and spin coating. A comparison of the differences of luminescent and optical characteristics of micro-and nanosized PMMA films doped with the anisometric Eu III complex is given. Based on X-ray powder diffraction and small-angle scattering data, it has been supposed that the association of Eu III complex molecules occurs in the voids of the PMMA matrix and is accompanied by the formation of a nanocrystalline phase. For films obtained by spin coating, a deeper microphase separation is demonstrated than by bulk polymerization. The dimensional characteristics of the nano-associates were determined and a correlation between the method of preparation and the type of distribution of the Eu III complex in the PMMA matrix is established.

Composites Based on Polylactide Doped with Amorphous Europium(III) Complex as Perspective Thermosensitive Luminescent Materials

“…Long hydrocarbon substituents at the edges of the synthesized complex do not favor its crystallization and allow to broadly vary the content of luminophore in polymer to achieve the maximum emission efficiency at high concentrations. As the authors demonstrated previously by studying a similar system with PMMA [47] and conjugated polymer (PVK) [46], higher content of the amorphous component in a polymer matrix does not lead to formation of larger aggregates and crystalline defects and the resulting self-quenching of luminescence as compared with analogous crystalline systems. Comparison of the emission spectra of the films with different Eu(III) content revealed that an increase in the luminophore concentration results in a nonlinear growth of its luminescence intensity, which reaches maximum at 17.5 wt% of the doped complex (Figure 3a).…”

“…In the previous work, we demonstrated that amorphous Ln(III) compounds dissolve well in organic solvents, mix with various polymers, and distribute uniformly in a polymer matrix due to their unique structural features (anisotropy of geometry and long hydrocarbon substituents on molecular edges) [46]. It allows to avoid formation of crystalline defects, neutralize the effect of luminescence self-quenching, and obtain a more efficient mechanism of intermolecular energy transfer as compared with known analogues [47]. Such complexes are efficient light absorbers in a broad spectral range of 250-400 nm, so it is not necessary to use hard UV radiation for their excitation [48,49].…”

Temperature-Sensitive Chameleon Luminescent Films Based on PMMA Doped with Europium(III) and Terbium(III) Anisometric Complexes

“…These complexes are amorphous powders that are soluble in organic non-polar and weakly polar solvents. They are mutually miscible as well as miscible with PMMA polymer [31,38].…”

Anisometric Ln(III) Complexes with Efficient Near-IR Luminescence

“…Ln(III) complexes [63] were synthesized according to the following general procedure: ethanol solutions of LnCl 3 × 6H 2 O (Ln = Pr, Nd, Sm, Gd, Ho, Er or Yb) (0.1 mmol) were added dropwise to a stirred hot ethanol solution that contained β-diketone (1-[4-(4propylcyclohexyl)phenyl]-octane-1,3-dione) (0.3 mmol), 1,10-Phenanthroline (0.1 mmol), and KOH (0.35 mmol). The resulting light-yellow precipitates were filtered from their solutions, washed by hot alcohol, and dried under vacuum.…”