|487. Löbling, T.I.; Haataja, J.S.; Synatschke, C.V.; Schacher, F.H.; Müller, M.; Hanisch, A.; Gröschel, A.H.; Müller, A.H.E.: Hidden Structural Features of Compartmentalized Nanoparticles Revealed by Cryogenic Transmission Electron Tomography, ACS Nano published online on September 8 (2014) -- DOI: 10.1021/nn504197y|
The demand for evermore complex nanostructures in materials and soft matter nanoscience also requires sophisticated characterization tools for reliable visualization and interpretation of internal morphological features. Here, we address both aspects and present synthetic concepts for the compartmentalization of nanoparticle peripheries as well as their in-situ tomographic characterization. We first form negatively charged spherical multicompartment micelles from ampholytic triblock terpolymers in aqueous media, followed by interpolyelectrolyte complex (IPEC) formation of the anionic corona with bishydrophilic cationic/neutral diblock copolymers. At a 1:1 stoichiometry of the anionic and cationic charges, the so-formed IPECs are charge neutral and thus phase separate from solution (water). The high chain density of the ionic grafts provides steric stabilization through the new neutral corona chains and suppresses collapse of the IPEC; instead, the dense grafting results in defined nanodomains oriented perpendicular to the micellar core. We analyze the 3D arrangements of the complex and purely organic compartments, in-situ, by means of cryogenic transmission electron microscopy (cryo-TEM) and tomography (cryo-ET). We study the effect of block lengths of the cationic and non-ionic block on IPEC morphology and while 2D cryo-TEM projections suggest similar morphologies, cryo-ET and computational 3D reconstruction reveal otherwise hidden structural features, e.g. planar IPEC brushes emanating from the micellar core.