Steric Constraints Induced Frustrated Growth of Supramolecular Nanorods in Water

• Published in: Chemistry : a European journal Vol. 21; no. 52; pp. 19257 - 19264
• Main Authors: Appel, Ralph, Fuchs, Jonas, Tyrrell, Sara M., Korevaar, Peter A., Stuart, Marc C. A., Voets, Ilja K., Schönhoff, Monika, Besenius, Pol
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 21.12.2015; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: amphiphiles; Anisotropy; Biomaterials; Biomedical materials; Chemistry; Contour matching; Electron microscopy; Isotropic material; Magnetic resonance spectroscopy; Monomers; Morphology; nanomaterials; Nanorods; Nanostructure; NMR; NMR spectroscopy; Nuclear magnetic resonance; Peptides; Polymerization; Polymers; Self assembly; supramolecular chemistry; Water based; amphiphiles; self-assembly; nanomaterials; polymers; supramolecular chemistry
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201503616

A unique example of supramolecular polymerisation in water based on monomers with nanomolar affinities, which yield rod‐like materials with extraordinarily high thermodynamic stability, yet of finite length, is reported. A small library of charge‐neutral dendritic peptide amphiphiles was prepared, with a branched nonaphenylalanine‐based core that was conjugated to hydrophilic dendrons of variable steric demand. Below a critical size of the dendron, the monomers assemble into nanorod‐like polymers, whereas for larger dendritic side chains frustrated growth into near isotropic particles is observed. The supramolecular morphologies observed by electron microscopy, X‐ray scattering and diffusion NMR spectroscopy studies are in agreement with the mechanistic insights obtained from fitting polymerisation profiles: non‐cooperative isodesmic growth leads to degrees of polymerisation that match the experimentally determined nanorod contour lengths of close to 70 nm. The reported designs for aqueous self‐assembly into well‐defined anisotropic particles has promising potential for biomedical applications and the development of functional supramolecular biomaterials, with emerging evidence that anisotropic shapes in carrier design outperform conventional isotropic materials for targeted imaging and therapy. Crowd restrictions: A unique supramolecular polymerisation in water based on non‐ionic dendritic peptide monomers with nanomolar affinities, which yield rod‐like materials with very high thermodynamic stability, yet of finite length, is reported (see figure). Below a critical size of the dendritic side chains, the monomers assemble into nanorod‐like polymers, whereas the use of a larger dendron leads to frustrated growth into small, near‐isotropic particles.