Self-assembly worm micelles

Block copolymers self-assemble to form nanoscale organized structures in a selective solvent. The most common structures are spheres, with the insoluble core surrounded by a solvent-swollen corona. In some instances, disk- or worm-like micelles form, and are of particular interest, since the control of their association can lead to a broad range of new applications [1,2]. An important subset of block copolymer micelles are those which contain metal atoms, through covalent attachment or by complexa-tion [3], These structures are interesting because they take advantage of the intrinsic properties of their components, such as the mechanical properties of the polymer micelles and the optical and magnetic characteristics of the metal atoms. Moreover, the assembly permits the control of the uniformity in size and shape of the nanoparticles, and it stabilizes them. 

Because of the interaction of the two complicated and not well-understood fields, turbulent flow and non-Newtonian fluids, understanding of DR mechanism(s) is still quite limited. Cates and coworkers (for example, Refs. " ) and a number of other investigators have done theoretical studies of the dynamics of self-assemblies of worm-like micelles. Because these so-called living polymers are subject to reversible scission and recombination, their relaxation behavior differs from reptating polymer chains. An additional form of stress relaxation is provided by continuous breaking and repair of the micellar chains. Thus, stress relaxation in micellar networks occurs through a combination of reptation and breaking. For rapid scission kinetics, linear viscoelastic (Maxwell) behavior is predicted and is observed for some surfactant systems at low frequencies. In many cationic surfactant systems, however, the observed behavior in Cole-Cole plots does not fit the Maxwell model. 

Fig. 10 Structure of a -((PEE)-(PEO)-(poly(/-methyl-e-caprolactone))) miktoarm block terpoly-mer, along with schematic representations and cryo-TEM micrographs of the resulting self-assembled micellar structures hamburger , segmented worm-like and raspberry micelles (from left to right). Reproduced with permission from [56]. Copyright (2008) American Chemical Society...

Linear amphiphilic glycopolymer conjugates that can self-assemble into well-defined nano- to micro-sized structures such as micelles, vesicles (polymersomes), a-helices, and worm-like aggregates are of increasing interest as means for drug... 

Abstract Amphiphilic polymers have the ability to self-assemble into supramolec-ular structures of great complexity and utility. Nowadays, molecular dynamics simulations can be employed to investigate the self-assembly of modestly sized natural and synthetic macromolecules into structures, such as micelles, worms (cylindrical micelles), or vesicles composed of membrane bilayers organized as single or multilamellar structures. This article presents a perspective on the use of large-scale computer simulation studies that have been used to xmderstand the formation of such structures and their interaction with nanoscale solutes. Advances in this domain of research have been possible due to relentless progress in computer power plus the development of so-called coarse-grained intermolecular interaction models that encode the basic architecture of the amphiphUic macromolecules of interest. 

Zhang and coworkers studied the differences between self-assembly of cyclic and linear nonionic amphiphilic copolypeptoids of Al-methyl- and A -decylglycine [117]. The differences were minor with respect to the final product but differed in the formation kinetics. Initially, spherical micelles formed in methanolic or aqueous solutions/suspensions. However, within a few days, both materials eventually formed cylindrical (worm-like) micelles. These micelles were only a few nanometers in diameter but several microns in length. 

Figure L Self-assembled OCL worm micelles spontaneously shorten to spherical miceller. a. Visualized by FM and cryo-TEM(inset,bar=100nm) b. Dynamic snapshots of single OCL worm micelle c. Contour length distributions. (Reproduced from reference 16. Copyright 2005 ACS)...

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