Ordering and Helical Structures of Nanoparticles in Block Copolymers

• Applicants: Professor Dr. Jens-Uwe Sommer; Professor Dr. Manfred Stamm
• Subject Area: Polymer Materials ; Experimental and Theoretical Physics of Polymers ; Solid State and Surface Chemistry, Material Synthesis ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 259030848

The aim of the proposed project is the control of complex structures formed by nanoparticles (NP) under block copolymer (BCP) confinement which surprisingly are observed. The purpose is to drive the nanoparticles inside of one of the BCP domains and, by exploiting confinement effects provided by BCP template, induce the nanoparticle self-assembly to form well-defined structures. Helical structures composed of optically active nanoparticles, such as silver or gold, are of particular interest. The nanoparticles will be synthesized and functionalized with polymer layer and then mixed with block copolymers to obtain NP/BCP composites with domain-selective NP arrangement. Our recent experimental results clearly demonstrate that under BCP confinement nanoparticles can self-assemble to form helical structures. There is limited information, however, about the possible mechanisms and parameters which determine and influence the helix formation. The ratio between the BCP domain size (host) and nanoparticle size (guest), the chain length and grafting density of particle-tethered polymer, the selectivity of solvent would play an important role. These parameters will be systematically varied and their impact on formation of NP helical structures under BCP confinement will be studied. With the aid of selective solvents NP/BCP composites will be converted into isolated nanoobjects, (i.e. nanofibers) bearing the nanoparticles assembled into helical structures. We expect that NP/BCP composites with helical nanoparticles assemblies may display specific optical properties, such as optical dichroic or light polarisation properties. Computer simulations will be used to guide structure formation in this multi-dimensional parameter space and provide an understanding of the self-assembly of nanoparticles under the block copolymer confinement. Here, both strongly selective solvents and the bulk phase of copolymers will be considered. The combination of experiment and simulation will help to understand details of formation of nanoparticle. We expect that this project can lead to the development of new functional materials with optical properties which can be tuned by the environment and by chemistry.

• DFG Programme: Research Grants