Aggregation states cross-linked structures

Janus micelles are non-centrosymmetric, surface-compartmentalized nanoparticles, in which a cross-linked core is surrounded by two different corona hemispheres. Their intrinsic amphiphilicity leads to the collapse of one hemisphere in a selective solvent, followed by self-assembly into higher ordered superstructures. Recently, the synthesis of such structures was achieved by crosslinking of the center block of ABC triblock copolymers in the bulk state, using a morphology where the B block forms spheres between lamellae of the A and C blocks [95, 96]. In solution, Janus micelles with polystyrene (PS) and poly(methyl methacrylate) (PMMA) half-coronas around a crosslinked polybutadiene (PB) core aggregate to larger entities with a sharp size distribution, which can be considered as supermicelles (Fig. 20). They coexist with single Janus micelles (unimers) both in THF solution and on silicon and water surfaces [95, 97]. 

FIGURE 16.3 Glycodendrimer-mediated protein aggregation in solution, (a) Structures of the Man-coated PAMAM dendrimers with G values referring to various dendrimer generations, (b) Transformation of uncomplexed Con A to the cross-linked state in the presence of a glycodendrimer. 

Fig. 2 (a-c) Physical polymer-network cross-linking provided by mixed micelles in hydrogels formed via hydrophobic interactions in surfactant solutions. Mixed micelles are formed by aggregation of hydrophobic blocks of per-se hydrophilic polymers and surfactant alkyl tails, (b) Nonionic polymer and ionic surfactant gel system at the state of preparation. For clarity, charges are not shown, (c) Ionic polymer and oppositely charged surfactant gel system after extraction of free micelles, (d) Structure of the hydrophobic monomers used in the micellar polymerization... 

Tew and Amt [92-94] have prepared amphiphilic meta-PPEs 58 and investigated their behavior at the air-water interface where they prefer an extended conformation. These PPEs are active in the lysis of phospholipid vesicles and might find application as bactericidal substances. While the derivative 58 with R = H forms clear solutions in water, the alkoxy-substituted congeners aggregate and precipitate out upon addition of water to their solution in DMSO. The structure of 58 in the solid state is assumed to be helical rather than extended. If acrylic ester substituents are placed on 59, it is possible to capture the helical intermediates by a photochemical 2-1-2 cycloaddition (Figure 6.2) [95,96]. The presence of a fixated helical structure was evident, because addition of chloroform to the cross-linked form did not... 

Enzyme biocomposites can also be designed without the participation of any solid support [108,109]. Such carrier-free immobilized enzymes can be prepared by direct cross-linking of the protein molecules in different physical states (e.g., dissolved, crystalline, spray-dried, or physically aggregated enzymes) leading to various structures [110]. 

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