Orientation of Nonspherical Nanoparticles in Ordered Block Copolymer for Functional Materials.

In the fields of controllable catalysis, electromagnetic field manipulation, and nanoscience, mediated self-assembly has become a key method for controlling the orientation of nonspherical nanoparticles. The ordered structures formed by block copolymer self-assembly can provide an orientation matrix for nonspherical nanoparticles. Based on self-consistent field theory, this study investigates the orientation effects of monaxially symmetric cylindrical nanoparticles in the lamellar phases formed by block copolymers. Using cylindrical and pore-containing ring nanoparticles as models for nonspherical particles, we successfully describe the particles' anisotropy and nonconvex surface properties. Numerical results show that the orientation effect of the lamellar ordered structure exhibits a nontrivial dependence on the geometric and topological properties of nonspherical particles. In addition to interfacial tension effects, the orientation mechanism of small-sized nanoparticles mainly arises from the stretching effect of the polymer, manifested in two main effects: (1) the particle deforms the polymer chain, reducing its conformational entropy, thus tending to align in a specific orientation; (2) the orientation field at the polymer chain ends is discontinuous, and the nanoparticles can embed and adopt a specific orientation. For nonconvex nanoparticles, the geometric size of the pore structure adjusts the polymer's free volume, influencing the orientation effect. This study not only deepens the understanding of the orientation mechanism in block copolymer-mediated nanoparticle self-assembly, but also provides potential theoretical insights for the design and application of energy catalysis, biomedical materials, and functional nanostructures.