Letter pubs.acs.org/macroletters
Rod-Like Nanoparticles with Striped and Helical Topography Jani-Markus Malho,†,‡,§ Maria Morits,†,‡ Tina I. Löbling,‡ Nonappa,‡ Johanna Majoinen,‡ Felix H. Schacher,∥,⊥ Olli Ikkala,*,‡ and André H. Gröschel*,‡,# ‡
Department of Applied Physics, Aalto University School of Science, FIN-02150 Espoo, Finland Laboratoire de Chimie des Polymères Organiques (LCPO), CNRS UMR 5629, Université de Bordeaux, Bordeaux-INP, Pessac 33607 Cedex, France ∥ Laboratory of Organic and Macromolecular Chemistry (IOMC) and ⊥Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, 07743 Jena, Germany # Physical Chemistry and Centre for Nanointegration (CENIDE), University of Duisburg-Essen, 45127 Essen, Germany §
S Supporting Information *
ABSTRACT: The behavior of nanoparticles in solution is largely dominated by their shape and interaction potential. Despite considerable progress in the preparation of patchy and compartmentalized particles, access to nanoparticles with complex surface patterns and topographies remains limited. Here, we show that polyanionic brushes tethered to rod-like cellulose nanocrystals (CNCs) spontaneously develop a striped or helical topography through interpolyelectrolyte complexation with polycationic diblock copolymers. Using cryogenic transmission electron microscopy (cryo-TEM) and tomography (cryo-ET), we follow the complexation process and analyze the delicate 3D topography on the CNC surface. The described approach is facile and modular and can be extended to other block chemistries, nanoparticles, and surfaces, thereby providing a versatile platform toward surface-patterned particles with complex topographies and spatially arranged functional groups.
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selection of chemistries allows for supramolecular engineering to generate complex nanopatterns.20−22 Among them, ionic complexation is an established and versatile tool to create architectures through supramolecular interaction of complementarily charged components.23−29 Interpolyelectrolyte complex (IPEC) formation between oppositely charged polyions significantly progressed toward intricate structures on the surface of spherical nanoparticles.30−33 The IPEC itself thereby becomes charge neutral under stoichiometric conditions and collapses into a hydrophobic compartment. To maintain solubility of the as-formed superstructure, di-, tri-, or multiblock copolymers with stabilizing neutral hydrophilic blocks are suited for complexation.34 We recently showed that the spatial competition between IPEC and stabilizing corona can lead to unusual surface asperities/topographies on spherical nanoparticles.35 Moreover, it has been suggested that even more intriguing IPEC morphologies could be achieved on anisotropic particles,36 however, such systems have not been realized so far. Here, we employ rod-like cellulose nanocrystals (CNCs)37 to investigate IPEC morphologies on anisotropic nanoparticles (Scheme 1). CNCs with a length of 100−200 nm and diameter of 5−10 nm are obtained via sulfuric acid hydrolysis, which
n recent years, approaches have been presented for the bottom-up assembly of particulate building blocks into mesoscopic superstructures aiming at complex composition, internal periodicities, and hierarchies.1−6 The quality of the superstructure depends on the level of control over interparticle interactions that may already become significant at distances orders of magnitude larger than the particle size itself.7 Particle shape (rod, cube, plate, etc.) and surface structure (e.g., spikes) become particularly relevant in crowded systems, where the interparticle distance is reduced to the order of the particle diameter.8 Proper attention should thus be paid to the particle surface controlling long-range directional interactions, assembly kinetics, and short-range particle recognition.9−12 Beyond decorating the particle surface with 2D patterns of varying chemistry (patches),13 also the topography can be tailored.14 While top-down methods are well suited to create microscopic colloids with various shapes and surface patterns,15−17 equipping nanoparticles (
