3D-Positioning of Nanoparticles in High-Curvature Block Copolymer Domains

The defined assembly of nanoparticles in polymer matrices is an important precondition for next-generation functional materials. Here we demonstrate that a defined three-dimensional nanoparticle assembly within the unit cells can be realized by directly linking the nanoparticles to block copolymers. We show that for a range of nearly symmetric to unsymmetric block copolymers there are only two formed structures, a hexagonal lattice of P6/mmm-symmetry, where the nanoparticles are located in 1D-arrays within the cylindrical domains, and a cubic lattice of Im3m-symmetry, where the nanoparticles are located in the octahedral voids of a BCC-lattice, corresponding to the structure of ferrite steel. We observe the block length ratio and thus the interfacial curvature to be the most important parameter determining the lattice type. This is rationalized in terms of minimal chain extension such that domain topologies with large positive curvature are highly preferred. Already volume fractions of only one percent are sufficient to destabilize a lamellar structure and favor the formation of highly curved interfaces. The study thus demonstrates how nanoparticles can be located on well-defined positions in three-dimensional unit cells of block copolymer nanocomposites. This opens the way to functional 3D-nanocomposites where the nanoparticles need to be located on defined matrix positions.

Automated summary

A defined three-dimensional nanoparticle assembly within unit cells can be achieved by linking nanoparticles to block copolymers. The study shows that the block length ratio and interfacial curvature are crucial factors determining lattice type, with even a one percent volume fraction enough to destabilize the structure and favor the formation of highly curved interfaces. This research paves the way for functional 3D-nanocomposites with nanoparticles located on specific matrix positions.