© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 wileyonlinelibrary.com COMMUNICATION modification of QDs with complex mesogen containing ligands, which resulted in the preparation of thermodynamically stable QDs solution in LC matrix, yet with still low concentration of the additive (0.25%). In the most of other papers devoted to QDs solutions in LC media the concentration of QDs does not exceed 0.1%. There are several recent works concerning the LC–QDs mixtures with higher concentration of the QDs. [21,22] Yet, these experimental results are in strong contradiction with other publications devoted to the similar mixtures and lack strong experimental proofs of the thermodynamic stability of these composites. In most cases, the methods of preparation of QD–LC com- posites are based on simple mixing of components in common solvent followed by spin coating or drying. [23,24] In some cases, bi- or multilayer films containing QDs-rich layers were pre- pared by sequential spin-coating method. [25,26] As a resume, from the literature data, we may conclude that the development of new methods for embedding of high amount of QDs in LC media without the loss in the optical properties of any of the component is still challenging and highly relevant. In the present paper, we propose a new method of preparation of stable QD–LC composites containing very high (up to 10 wt%) amount of QDs. The idea of the elaborated procedure is schematically depicted in Figure 1. On the first stage, the polymer-stabilized LC film (with any type of LC phase) is prepared (Figure 1a). For this purpose, LC mixture consisting of ≈10% of meso- genic diacrylate, ≈15% of LC monoacrylate, ≈75% of low- molar-mass LCs and 1%–2% of photoinitiator (see Table 1) is placed into asymmetrical cell with two glass substrates coated by different polymer layers — polyvinyl alcohol (PVA) and polyvinyl-cinnamate (PVCin). Rubbing of the substrates with polymer layers allows one to achieve uniaxial orientation of LCs molecules. UV irradiation of these cells leads to photopo- lymerization of acrylates. The presence of reactive C C double bonds in the cinnamate fragment of PVCin warrants a good adhesion of polymer network to PVCin-coated glass substrate, which makes mechanical removal of the PVA-coated glass plate (Figure 1b) on the next stage more easy. The LC film obtained after photopolymerization has microheterogeneous structure consisting of LC polymer network and low-molar- mass LC microphase. Nevertheless, under appropriate irradia- tion conditions (light intensity, monomers, and photoinitiator structure and their concentration), characteristic dimensions of these microphases are comparable or even smaller than the wavelength of visible light, which minimizes light scattering of LC-composite films. [20,21] LC-polymer network stabilizes the alignment of the LCs molecules, and has the possibility An Effective Method for the Preparation of Stable LC Composites with High Concentration of Quantum Dots Alexey Bobrovsky,* Pavel Samokhvalov, and Valery Shibaev Dr. A. Bobrovsky, Prof. V. Shibaev Faculty of Chemistry Moscow State University Leninskie gory, Moscow 119991, Russia E-mail: bbrvsky@yahoo.com Dr. P. Samokhvalov Laboratory of Nano-Bioengineering National Research Nuclear University MEPhI (Moscow Engineering Physics Institute) Moscow 115409, Russian Federation DOI: 10.1002/adom.201400215 Organic–inorganic hybrid materials, in particular, liquid crys- tals doped with nanoparticles, quantum dots (QDs) and other nanometer-scale colloid particles attract a great attention of large number of research groups due to their unique optical properties, switchability, and the variety of possible applications in optics, optoelectronics, and photonics. [1–19] Cholesteric liquid crystals doped with QDs present a special interest because the photonic bandgap structure of cholesteric media when combined with emission properties of QDs pro- vides the opportunity to realize a variety of specific photooptical properties. Cholesteric mesophase has a 1D photonic bandgap structure, which stands for its unique optical properties such as Bragg selective light reflection, huge optical rotation, and so on. [20] In several recent papers, the optical and photophys- ical properties of the cholesteric low-molar-mass and polymer liquid crystalline (LC) materials doped with QDs were dem- onstrated. [16–18] For example, in recent publication, [16] the modulation of recombination lifetimes of CdSe/ZnS QDs (0.01–0.02 wt%) dispersed in cholesteric low-molar-mass liquid crystal and time-resolved emission from QD ensembles in LC matrices with different alignment were investigated. The differ- ence in decay time characteristics of QD’s emission depending on planar or homeotropic alignment was revealed in the case of overlapping of emission and photonic bandgap peaks. It was shown that coupling between the excitonic and the photonic cavity modes leads to the enhancement and modulation of spontaneous emission. In the papers [18,19] we have described the novel types of cho- lesteric QDs-doped materials with photo- and electro-tunable fluorescence. The possibility of manipulation of fluorescence intensity and degree of circular polarization (dissymmetry factor) was demonstrated for the first time. Despite a great progress in the field of the QD–LC compos- ites, the introduction of large concentration of QDs into liquid crystal media is still a challenging task. The most successful achievement in the area was published recently. [15] The authors of this work have offered an approach based on the surface Adv. Optical Mater. 2014, DOI: 10.1002/adom.201400215 www.MaterialsViews.com www.advopticalmat.de