Rod-shaped 1D polymer-assisted anisotropic self-assembly of 0D nanoparticles by a solution-drying method

Unidirectional assembly of 0D nanoparticles in a controlled manner is still a challenging task because of the intrinsic geometrically isotropic structure of 0D particles. Herein, we show that geometrically anisotropic 1D rod-shaped polymers facilitate the unidirectional assembly of clusters of 0D nanoparticles. Systematic investigations were performed using poly(phenyl isocyanide) (PPI) as a well-defined 1D anisotropic rod-shaped polymer and fullerene C-60 as a model crystalline 0D small organic molecule. We demonstrated that high-aspect-ratio PPIs with non-branched alkyl side chains facilitated the 1D assembly of C-60 crystals into ultralong whiskers and fibres exceeding 1 mm length with a diameter of ca. 1 mu m, where the C-60 crystals were phase separated from PPI and solvent molecules by a solution-drying process. Our methodology was also applicable to other small organic building blocks like fullerene C-70, 5,6,11,12-tetraphenylnaphthacene, tetraphenylethylene, and tetraphenylporphyrin to afford 1D molecular assemblies such as elongated whiskers, fibres, and dendritic structures. Furthermore, the addition of inorganic superparamagnetic iron-oxide nanoparticles (FeNP) into C-60 toluene solution resulted in the formation of highly anisotropic FeNP cluster assemblies along the ultralong C-60 fibres. We propose that the anisotropic depletion effect and the interfacial capillary force on the solution-drying process are the key factors for highly anisotropic assemblies of nanoparticle clusters. Since PPIs are readily modified, we believe that this study will pave a new way in the field of more functional rod-shaped polymers and creation of hierarchical crystalline materials.