Janus Micelles Induced by Olefin Metathesis

Abstract

A facile one-step procedure for hydrophobic modification and simultaneous TEM contrast enhancement via a regioselective olefin metathesis reaction using Grubbs' catalyst is presented. Polyether diblock copolymers were investigated, and both the chain ends of the hydrophilic and the hydrophobic block were hydrophobically modified. Modification of the hydrophilic block results in nonsymmetric supramolecular structures (Janus micelles) which self-assemble into larger hierarchically organized super-micelles.

Janus Micelle Formation Induced by Protonation/Deprotonation of Poly(2‐vinylpyridine)‐block‐Poly(ethylene oxide) Diblock Copolymers

“…[29] It has been reported that one of the characters of Janus micelles is their self-assembly into larger aggregates or supermicelles. [4d,20] As shown in Figure 3(d), the Janus micelles can further self-assembly into larger ill-defined aggregates upon equilibrating for long time, which is consistent with the result reported by Wurm et al [20] It can be seen the dark and most insoluble parts surrounding a central light grey core composed of PEO blocks [ Figure 3(D)]. This might be understood as follows.…”

“…The copolymer attached ruthenium complexes at PEO chain ends can form Janus micelles in tetrahydrofuran (THF)/water mixture. [20] The self-assembly of diblock copolymers has been investigated intensively. In selective solvents, block copolymers can self-assemble into various microstructures, such as sphere, cylinder and bilayer membrane, helices, cylindrical networks, nanotubes, the hollow hoop, the bowl-shaped micelles and the ringlike supramolecular assemblies.…”

Streng zweiphasige weiche und harte Janus‐Strukturen – Synthese, Eigenschaften und Anwendungen

“…Kürzlich wurde die katalytische Aktivität von zweiphasigen TiO 2 /Au-Janus-Nanopartikeln bei der Reduktion von 4-Nitrophenol zu 4-Aminophenol mit Natriumborhydrid nachgewiesen, die zu 99 % Umsetzung innerhalb von 6 min führte. [11] Für die Herstellung von Janus-Strukturen wurden viele Syntheseverfahren entwickelt, wie Selbstorganisation, [12][13][14][15][16][17] Mikrofluidik, [18][19][20] zweiphasiges Jetting, [21][22][23] Alkenmetathese, [24] Protonierungs-Deprotonierungs-Zyklen [25] und andere mehr. [26][27][28][29] Es existieren mehrere Übersichtsartikel, in denen Syntheseverfahren, Eigenschaften und Anwendungen von Janus-Strukturen aus unterschiedlichen Blickwinkeln beschrieben werden.…”

Polymeric Janus Particles

“…Recently our group reported the formation of Janus micelles after an olefin metathesis reaction of vinylether-initiated PEO-b-PPO diblock copolymers (PPO = poly(propylene oxide)) with Grubbs first-generation catalyst. This olefin metathesis reaction modifies the chain end of the block copolymer with an [56] In water, these modified polyethers form Janus structures, which could be visualized by TEM; as is typical for Janus particles, unimolecular micelles and ill-defined superstructures form. After longer equilibration times, the latter structures transform into well-defined supermicelles.…”