ИСТИНА

Block copolymers are well-studied self-organizing media, which can form various ordered structures with dimensions from one to hundreds nanometres. Such structures are widely tunable by changing molecular masses of the blocks, adding selective agents, or applying external fields. The resulting patterns can be used for the controlled deposition of different inorganic nanoparticles (NPs). Au NPs, in particular nanorods (NRs), are well known due to their unique optical characteristics, namely, high values of the absorption coefficient and scattering in the UV and visible light ranges related to localized surface plasmon resonance phenomena. Since the properties of NPs depend on their size, shape, and spatial arrangement, the properties of a composite material can be changed by altering the distribution of NPs in the host matrix. Microphase separation in block copolymers can lead to the formation of periodic structures of embedded NPs, provided they have different chemical affinity to the blocks. As a rule, an appropriate functional stabilizer is required to prevent the aggregation of NPs. In the present study, high molecular weight diblock copolymers of 2-vinylpyridine and 4-vinylpyridine with styrene (PS-P2VP and PS-P4VP) were used as stabilizers and host matrices for waterborne Au NRs. After the synthesis, such particles are weakly stabilized with cetrimonium bromide and it is complicated to use them in different solvents because of the irreversible aggregation during solvent replacement. We proposed to use PS-P2VP and PS-P4VP copolymers as phase transfer agents via the rapid stabilizer exchange accompanied with the transfer of Au NRs to organic media [1]. Irrespectively of the nitrogen position in vinylpyridine, P2VP or P4VP domains can directly interact with Au surface. The weak interaction of Au with a single chemisorbed pyridine ring is compensated by a large number of interacting groups in vinylpyridine blocks wrapping around NRs. Synthesized copolymer-stabilized Au NRs of ca. 9×30 nm size (Fig.1 left) are readily dispersible in a series of organic solvents (CH2Cl2, CHCl3, benzene, toluene, THF). The stability of Au NRs was proven by multiple cycles of vacuum drying and redispersing. Thin films of Au NRs in block copolymer matrices were made by spin casting followed by solvent vapor annealing. The resulting structure of P4VP vertical cylinders (Fig.1 right) demonstrates the localization of Au NR in polyvinylpyridine domains perpendicularly to the cylinder axes [2]. Thus, using block copolymers allows us to obtain ordered composites with Au NRs without any additional stabilizers. 1 Y.I. Derikov, G.A. Shandryuk, R.V. Talroze, A.A. Ezhov, Y.V. Kudryavtsev, Beilstein. J. Nanotechnol. 2018, in press 2 Y.I. Derikov, C. Abetz, G.A. Shandryuk, R.V. Talroze, A.A. Ezhov, V. Abetz, Y.V. Kudryavtsev, M.A. Osipov Polym. Sci., Ser C 2018, in press