Thermally stable glassy luminescent cyclotriphosphazenes

Abstract

A series of thermally stable cyclotriphosphazenes, hexakis(4-(9,9- dihexthyl-fluoren-2-yl)phenoxy)cyclotriphosphazene (CPZ1), hexakis(4′-(9, 9-dihexyl-fluoren-2-yl)-[1,1′-biphenyl]-4-oxy)cyclotriphosphazene (CPZ2), hexakis(4-(9,9,9′,9′-tetrahexyl-[2,2′-bifluoren]-7-yl)phenoxy) cyclotriphosphazene (CPZ3), and hexakis-(4′-(9,9,9′,9′- tetrahexyl-[2,2′-bifluoren]-7-yl)-[1,1′-biphenyl]-4-oxy) cyclotriphosphazene (CPZ4), were prepared by reacting hexachlorocyclotriphosphazene with suitable precursors in high yields. The chemical structures and properties of the compounds CPZ1-4 were characterized by thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, and UV-Vis and fluorescence spectroscopy. All CPZ compounds were amorphous in nature and showed very good thermal stability with decomposition temperatures of more than 429 C in nitrogen and around 400 C in air. CPZ3-4 emitted blue light with maxima of 403 and 416 nm with quantum yields of 0.69-0.56 in THF solution, respectively. Study on the thermal aging effect on the optical properties of CPZ2-4 revealed that three-dimensional hybrid organic-inorganic cyclotriphosphazene ring could suppress the undesirable green emission by obstructing π-π stacking. In addition, light-emitting diode devices of CPZ3 and CPZ4 were fabricated. © 2013 Elsevier Ltd. All rights reserved.