Monochelic copolymer as a matrix for cholesteric composites with gold nanoparticles

Abstract

Copolymer 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 gold nanoparticles (NPs). 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. Modification of the terminal groups of the copolymer does not change the type and properties of its liquid crystal phase. The monochelic copolymer obtained by modifying residue of RAFT agent located at the end of the main chain. The separation of the functional group that binds to NP and the mesogenic groups allows creating liquid crystalline (LC) material containing exceptionally high concentration of (up to 30 wt %) of gold NPs (∼4.8 nm in size). 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 nanoparticles.