ИСТИНА

Liquid crystal (LC) polymers and copolymers based on acrylic acid derivatives containing mesogenic groups in the side chains and thiol group at the end of the backbones has been synthesized to create a liquid crystal cholesteric composite with the nanoparticles (NPs) such as colloidal gold and CdSe quantum dots (QDs). LC structure was determined by the structure of the pendant (side chains) units. These LC were nematic, chiral nematic (cholesteric) and smectic. Reversible addition fragmentation chain transfer (RAFT) polymerization carried out using asymmetric agent makes easy producing monochelic macromolecules with mesogenic groups in the side chains and functional end-groups. The monochelic polymers and copolymers obtained by modifying residue of RAFT agent located at the end of the main chain. It was shown that the modification of the terminal groups of the copolymer to thiol group does not change the type and properties of its liquid crystal phase. The presence of thiol groups allows one to consider these polymers and copolymers as a functional monochelic system capable of interaction with NPs of noble metals like gold. The experimental results show that the cholesteric copolymer is the most friendly for gold NPs with the preserving of the LC ordering of the matrix. A new nanocomposite preserving LC order with a high content (at least up to 30 wt. %) of NPs (~4.8 nm in size) was successfully prepared.1 It has been shown that in the case of CdSe QDs interaction between the surface of NP and the polymer occurs due to both thiol groups and carboxyl groups of mesogens. The monochelic polymer matrix allows obtaining the content of CdSe QDs in the composite with the cholesteric LC structure which is at least 23 wt. %. LC order of composites is confirmed by transmission electron microscopy, luminescent microscopy and spectroscopic polarimetry. The distribution of NPs in the composite film is uniform and does not interfere with the LC order of the matrix. This ordering takes place on a scale which corresponds to at least micron-sized cholesteric domains. The thin films obtained demonstrate the coexistence of optical properties of both cholesteric liquid crystals with a stop band and plasmonic gold NPs. In the case of CdSe QDs ellipticity of the photoluminescence is observed. This effect is caused by the overlap between luminescent band of the QDs and the stop band of the cholesteric LC structure of the composite. Thus, it is shown that the separation of mesogenic groups and functional groups that can bind to NPs significantly improves the compatibility of NPs with a polymer matrix. Such an approach could be the basis of obtaining composites that retain the LC order and control the properties of nanoparticles.