Micellar fibers

Fig. 14 TEM micrographs showing a vesicles, b, c micellar fibers, and d superhelices from a PEO-PMPS block copolymer (the chemical structure of this copolymer is represented below the micrographs). Reprinted with permission from [238]. Copyright (2001) American Chemical Society...

Fig. 55a. In the presence of detergents, e.g. SDS, micellar fibers do not rearrange to crystals, because crystallization nuclei with head-to-tail sheets cannot be formed, b Electron micrograph of a 2-month-old gluconaniide D-28-8 gel, which was kept at 60 °C in the presence of SDS (molar ratio 10 1). Micelles and double helices occur (PTA 2% post-strained, bar = lOOnm). c Electron micrograph of a gel, which was kept at 20 °C and contained more SDS (molar ratio 2.5 1). Vesicles and multiple helices are apparent (PTA 2% poststained, bar — lOOnm) [377]...

Figure 6.11 Examples of biohybrid catalytic systems, (a) Covalent coupling of a polystyrene tail to the enzyme CALB lipase the resulting biohybrid forms micellar fibers, (b) Cofactor reconstitution A polystyrene tail is connected to the horseradish peroxidase enzyme via the cofactor ferri-protoporphyrin IX. the resulting...

The observed structures were explained by a chiral bilayer effect mechanism proposing that only the enantiomerically pure compounds can lead to the formation of helical fibers which in turn slowly rearrange to enantiopolar crystal layers (Scheme 7.1). Within the micellar fibers, the polar head groups are oriented toward the aqueous environment and must therefore go through an energetically unfavourable -slow- dehydration followed by a 180 ° to form the enantiopolar crystals. 

FIGURE 7.34. Top structure of PEO-PMPS block copolymer. Bottom transmission electron micrographs showing the formation of (a) vesicles, (b, c), micellar fibers, and (d) superhelices from this block copolymer. Reproduced with permission from the American Chemical Society. 

FIGURE 7.44. Transmission electron micrographs of the micellar assemblies formed by the aggregation of a lipase-polystyrene giant amphiphile in water. Expansion reveals a single micellar fiber with a diameter of 20-30 nm. Schematic representation of the micellar rod which possesses a polystyrene core. 

Yamada et al. described the formation of reverse micellar fibers in organic solvents using aggregates of tripeptide containing amphiphiles [71]. The tripeptide units in these aggregates were shown to possess a parallel chain (5-sheet structure that was present not only in water but also in carbon tetrachloride. 

Fig. 20 Micellar fibers of PMPSnPEOtn in mixtures of THF and water (25/75 by volume). TEM images (a) visualizing the poly silane core of miceUar fibers (unstained, bar represents 250 nm) (b) revealing the PEO shell using nranyl acetate staining, (c) showing an example of the bulges found for many of these fibers, (d) Schematic representation of the structure of the micellar fibers showing the PMPS core and the PEO shell. Reproduced with permission from [79], Sommerdijk et al. (2000) Macromolecules 33 8289. American Chemical Society...

The number of known organogelators whose luminescent properties should be investigated is large and growing. For instance, the previously mentioned rods of metalloporphyrins in cyclohexane might have interesting electron-transfer (and luminescence) properties like those of micellar fibers of octopus porphyrin in... 

Similar assemblies have been extensively characterized for the ion pair cetyltrimethylammonium-salicylate. In both cases the micellar fibers produce slightly viscous solutions and the effect of viscoelasticity is observed if one rotates such a solution and suddenly stops the rotation, smalt particles in the solution (e.g., air bubbles) bounce back. While the bulk water is still rotating in the nonviscous solutions, the inertia of the high molecular weight threads builds up an elastic wall for the suspended particles and pushes them back. Lithium and sodium ricinolates produce helical micellar fibers of opposing chirality in toluene (Tachibaona, 1970,1978). 

Figure 4.2.5 Solid-state CPMAS- C-NMR spectra of (a)iV-octyl-D-gluconainide, (b)-gulonamide, (c)-D,L-gluconamide crystals, and (d) -D-gluconamide micellar fibers (see Fig. 4.5.6). The corresponding molecular conformations are given. Note Soft racemate crystallites (c) and micellar fibers (d) have the same headgroup conformation.

Transmission electron microscopy of such a gel shows micellar fibers, which are several micrometers long and about 8 nm wide. Image analysis reveals regular quadruple helices of molecular bilayer rods or ribbons (Fig. 4.5.8). In cryo-electron microscopy the single helices appear somewhat broader (Fuhrhop et al., 1988 Koning et al., 1993). 

Fuhrhop, J.-H., Krull, M. (1991). Self-assembling lipid membranes—from planar bilayer sheets to cloth-like aggregates of micellar fibers, Frontiers in Supramolecular Organic Chemistry and Photochemistry (Schneider, H.-J., Diirr, H., eds.), VCH, Weinheim. 

Fuhrhop, J.-H., Spiroski, D., Schnieder, P. (1991). Two polymeric micellar fibers with gluconamid head groups. Reactive Polym., 15 215. 

Svenson, S., Koning, J., Fuhrhop, J.-H. (1994b). Crystalline order in probably hollow micellar fibers of A-octyl-D-gluconamide, J. Phys. Chem., 98 1022. 

Considering that amphiphihc porphyrins may either form micellar fibers or vesicles or they may be integrated into corresponding host systems, Fuhrhop et aL [91] prepared several N-glycosylamide protoporphyrin-IX derivatives (Fig. 9). 

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