Self-assembled block copolymer aggregates

Blanazs A, Aimes SP et al (2009) Self-assembled block copolymer aggregates from micelles to vesicles and their biological applications. Macromol Rapid Commun 30 267-277... 

Fig. 2 Self-assembled block-copolymers aggregates of different morphologies spherical (i = 3), cylindrical (i = 2), lamellar (i = 1). Hydrophobic blocks B and polyelectrolyte blocks A form the core and the corona of the micelle, respectively...

Figure 9 Self-assembled block copolymer aggregates of different morphologies spherical (/=3), cylindrical ( =2), lamellar ( =1). Insoluble B blocks and soluble A blocks are forming the core and the corona, respectively.

The first self-assembling block copolymers were PS-fe-PMPS- -PS synthesised by Matyjaszewski and Moller. They observed micellar aggregates by ATM after casting dilute dioxane solutions (a solvent selective for the PS block) of the copolymer. The observed micelles were taken to have internal PMPS cores and were measured at 25-30nm in diameter [73], The hrst self-assembling amphiphilic polysilane block copolymers to be investigated was the PMPS-PEO multi-block copolymer with normal distribution PMPS blocks and uniform low polydispersity PEO blocks. After dialysis aqueous dispersions of this copolymer formed micellar as well as vesicular structures [78, 79] as shown in Eig. 19. 

Another of the most fascinating properties of block copolymers is their ability to self-assemble into micelles, aggregates, and vesicles of various morphologies in the presence of a selective solvent, [117,118] and recent studies have demonstrated that self- assemble of amphiphilic block copolymers into various morphologies occurs not only in selective solvents but also at interfaces and surfaces [119,120],... 

The polymerization-induced self-assembly is a facile, efficient, and reproducible strategy for preparation of families of polymeric nanoparticles having various morphologies via a one-pot process. Direct preparation of the block copolymer aggregates in the dispersion and emulsion polymerizations at high concentration of sohds provides the possibihty for large-scale industrial production. Preferentially, the polymerization-induced self-assembly should be conducted in aqueous media at quantitative monomer conversion. 

Sun J-T, Hong C-Y, Pan C-Y (2012) Formation of the block copolymer aggregates via polymerization-induced self-assembly and reorganization. Soft Matter 8 7753-7767... 

AB diblock copolymers in the presence of a selective surface can form an adsorbed layer, which is a planar form of aggregation or self-assembly. This is very useful in the manipulation of the surface properties of solid surfaces, especially those that are employed in liquid media. Several situations have been studied both theoretically and experimentally, among them the case of a selective surface but a nonselective solvent [75] which results in swelling of both the anchor and the buoy layers. However, we concentrate on the situation most closely related to the micelle conditions just discussed, namely, adsorption from a selective solvent. Our theoretical discussion is adapted and abbreviated from that of Marques et al. [76], who considered many features not discussed here. They began their analysis from the grand canonical free energy of a block copolymer layer in equilibrium with a reservoir containing soluble block copolymer at chemical potential peK. They also considered the possible effects of micellization in solution on the adsorption process [61]. We assume in this presentation that the anchor layer is in a solvent-free, melt state above Tg. The anchor layer is assumed to be thin and smooth, with a sharp interface between it and the solvent swollen buoy layer. 

The formation of polymeric capsules can also be achieved by the cross-linking of self-assembled amphiphilic block copolymers [85]. The hydrophobic section of the polymer in an aqueous solution will tend to aggregate on the interior of the micelle, whereas the hydrophilic ends will form the outer shell of the micelle. If the hydrophilic end is appropriately functionalized, it can be cross-linked, giving a polymeric shell. The overarching concept is shown in Figure 5.10. 

In this section the emphasis will be on assemblies prepared from amphiphilic dendrimers. Amphiphilic dendrimers, carrying both hydrophobic and hydrophilic regions within one molecule, tend to self-assemble into a large variety of different aggregates depending on their structure. The dendritic amphiphiles investigated so far include unimolecular micelles, bolaamphiphiles, superam-phiphiles and various other AB and ABA block copolymers. 

The addition of large linear blocks to dendrons with opposite polarity creates a desymmetrized structure predisposed to sequester insoluble components by aggregation rather than intramolecular hydrogen-bonding. Amphiphilic, linear-dendritic diblock (AB) and triblock (ABA) copolymers self-assemble into multimolecular micelles with CMC values that are well below those of low molecular weight surfactants. Typically, a hydrophilic linear block such as PEG is attached to the focal point... 

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