Micelles onion-like

Figure 6.37. Synthetic scheme for three-layer cross-linked micelles. Shown is the micellation of poly[(ethylene oxide)-block-glycerol monomethacrylate-block-2-(diethylamino)ethyl methacrylate] (PEO-GMA-DEA) triblock copolymers to the final onion-like" layered nanostructure. Reproduced with permission from Liu, S. Weaver, J. V. M. Save, M. Armes, S. P. Langmuir 2002, 18, 8350. Copyright 2002 American Chemical Society.

Fig. 13 Onion-like core (A)-sheU (B)-corona (C) structure of the micellar IPEC formed upon interaction between PIB-b-PMANa micelles and P4VPQ. Reprinted from [67] with permission from Elsevier...

Fig. 4 Representation of the various types of internal organisation that may occur in micelles formed through co-assembly of charged block copolymers. Depicted are micelles with a corona consisting of two different neutral monomers (shown in blue and green) that are (a) mixed, (b) laterally segregated, (c) radially segregated, and (d) laterally and radially segregated. Both cen-trosymmetric micelles (a, c) and non-centrosymmetiic micelles (b, d) are depicted. The micelle with a laterally segregated corona is generally referred to as a Janus micelle (b). The micelle depicted in (c) is most commonly known as onion-like or core-shell-corona micelle. The micelle with a laterally and radially segregated corona (d) is usually called a patched micelle. Note that in the case of (c) and (d) the blue and the red/black chains may also switch position...

Xas = 1, and xab = 0. The chains are grafted in the XY plane and (f>f denotes the polymer density. The plots marked B show the polymer density of the B blocks, while the plots marked A show the density of the A blocks. In (a), the A layer coats the more solvophobic B core and the micelle resembles an onion-like structure. In (b), the long A blocks shield multiple B cores and the structure resembles a garlic... 

In dispersions stabilized on the basis of phospholipids, an additional fraction of very unstable particles was detected in the cryo-preparation. These particles possibly have a spherical shape as particles with an onion-like structure were detected in the freeze-fracture preparations. Due to the layered structure of the smectic phase, a cylindrical particle shape should be energetically more favorable than a spherical one. This may also be the reason for the higher sensitivity of spherical particles towards the electron beam. In formulations with polymeric stabilizers (e.g. poloxamer, polyvinyl alcohol and Tween 80), such highly unstable particles have not been detected yet. Polymer-stabilized smectic nanoparticles possess a more round, paving-stone-like particle shape. In dependence on the stabilizer system, additional colloidal structures (e.g. vesicles and micelles) formed by the excess of emulsifiers could be detected as well (Fig. 10.11). 

Aqueous solutions of didodecyldimethylammonium bromide (DDAB) exhibit an interesting self-assembly phenomenon." Each amphiphilic molecule of DDAB has two hydrophobic tails, so that DDAB molecules spontaneously form inverted micelles in hydrocarbons and nano-size spherical vesicles in dilute aqueous solutions. However, in aqueous solutions, at the DDAB concentration of about lO moldm , the spherical vesicles self-assemble into a multilayer onion-like structure shown in Figure 7.3. It is also notable that at the same DDAB concentration, the interfacial tension between water and a hydrocarbon (octane) almost vanishes, becoming less than 0.1 mNm and suggesting that the formation of the multilayer structure may be accompanied by water-oil interface instability. 

Fig. 10 (a) Onion-like core-shell-corona structure of IPECs formed by the star-like PIB-h-PMACs micelles (HPE) with the linear P4VPQ (GPE). Reprinted from [61] Copyright 2004 with permission from Elsevier, (b) Cryo-TEM image of the micellar IPECs. Reprinted with permission from [62] Copyright 2008 American Chemical Society... 

Fig. 1 Schematic representation of co-assembly of two oppositely charged ionic-neutral diblock copolymers in water into complex coacervate core micelles, in short C3Ms, with a core comprising the oppositely charged monomers surrounded by a shell of neutral, water-soluble monomers. The two monomer types in the corona may mix left) or segregate radially (mid-left), laterally (mid-right) or both radially and laterally (right) depending on the chemical composition of the block copolymers and hence the miscibility and differential solvent quality of the neutral monomers. This may lead to the formation of onion-like micelles, also known as core-shell-corona structures (mid-left), Janus micelles (mid-right) or patchy micelles, also known as raspberry-like micelles (right). Figure from Ref. [188]...

Core-shell-corona or onion-like micelles were reported by Zhang et al. [78]. Spherical core-shell micelles were first prepared from the amphiphilic block copolymer PS- -PAA in ethanol. Further addition of PEO- -P4VP block copolymer... 

As introduced previously, onion-like or core-shell-corona micelles were also reported in complexes formed via... 

Initially, micelles with P2MVP/PAA complex core and randomly mixed PEO/PNIPAM corona were observed. At temperatures greater than 60 C, onion-like micelles with PNIPAM core, P2MVP/PAA complex shell, and PEO... 

Cai, G., Zhang, H., Liu, R, Wang, L., Jiang, H. (2011]. Triggered disassembly of hierarchically assembled onion-like micelles into the pristine core-shell micelles via a small change in Ph, Acta Biomater., 7, 3729-3737. 

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