Hybrid fluorescent liquid crystalline composites: directed assembly of quantum dots in liquid crystalline block copolymer matrices

Abstract

Hybrid fluorescent liquid crystalline (LC) composites containing inorganic quantum dots (QDs) are promising materials for many applications in optics, nanophotonics and display technology, combining the superior emission capability of QDs with the externally controllable optical properties of LCs. In this work, we propose the hybrid LC composites that were obtained by embedding CdSe/ZnS QDs into a series of host LC block copolymers of different architectures by means of a two-stage ligand exchange procedure. The ABA/BAB triblock copolymers and AB diblock copolymers with different polymerization degrees are composed of nematogenic phenyl benzoate acrylic monomer units and poly(4-vinylpyridine) blocks, which are capable of binding to the QD surface. Our results clearly show that the spatial distribution of QDs within composite films as well as the formation of QD aggregates can be programed by varying the structure of the host block copolymer. The obtained composites form a nematic LC phase, with isotropization temperatures being close to those of the initial host block copolymers. In addition, the influence of the molecular architecture of the host block copolymers on fluorescence properties of the obtained composites is considered. The described strategy for the QD assembly should provide a robust and conventional route for the design of highly ordered hierarchical hybrid materials for many practical applications.