Highly luminescent soft aggregates and films assembled by amphiphilic polyoxometalate complex in a polymerizable aprotic ionic liquid

Abstract

Hybrid co-assembly from lanthanide-containing polyoxometalates (POMs) and surfactants could efficiently optimize the formed aggregate luminescent properties and structural diversity. Meanwhile, compared to conventional solvents, aprotic ionic liquids (ILs) are not only excellent assembly media but also ideal solvents for luminescent lanthanide compounds. Therefore, in this work, the luminescent amphiphilic POM complex, namely surfactant-encapsulated POM hybrid (SEP) was initially prepared mainly through electrostatic interaction from polyanionic lanthanide-containing POM, Na9(EuW10O36)·32H2O (EuW10) and cationic surfactant, 1-octadecyl-3-methylimidazolium bromide ([C18mim]Br, OB). Then, highly luminescent lamellar micro-fiber aggregates were assembled by SEP in a polymerizable imidazolium-IL solvent, i.e. 1-vinyl-3-butyl imidazolium terafluoroborate ([Vbim]BF4). After morphology and structure characterizations for soft aggregates in detail, a lamellar aggregation arrangement mechanism was proposed. Further through in situ photopolymerization for such aggregate matrices, the flexible and organized films with enhanced luminescent properties were obtained. Our work indicates that the rational design of polymerizable organized aggregate matrices in ILs could greatly improve the photophysical properties of such luminescent soft materials and also expand their practical applications.