Side-chain Self-assembly

In 2004, Week and co-workers demonstrated that both mono- and multifunctional self-assembly could be employed simultaneously independently and reversibly on the same side-chain functionalized polymer [96]. A random terpolymer of poly(norbornene) was synthesized consisting of diaminopyridine (DAP) hydrogen-bonding receptors and a palladium-functionalized SCS-type pincer ligand for metal coordination-based self-assembly (Fig. 7.18). 

Initially, Week and co-workers demonstrated that controlled, multi-self-assembly in this system can be achieved either in a stepwise fashion or in a one-pot procedure (Fig. 7.19). 

Finally, Week s group has also investigated the incorporation of two distinct hydrogen-bonding receptors (Fig. 7.21) along a single polymer backbone (both random and block copolymers were investigated) [93, 95]. 

The selective self-assembly of a receptor molecule with its complementary recognition unit in the presence of a competitive recognition unit has been described as self-sorting in the literature. DNA and RNA are the prime examples of this concept. Using the above-described copolymers containing two hydrogenbonding units, Burd and Week [95] were able to prove this concept of self-sorting also in synthetic polymer systems (Fig. 7.22). 

The independent, noninteracting behaviors of these two modes of self-assembly allowed for the creation of a self-assembled, multifunctional, reversible, cross-linked material in one self-assembly step. This simultaneous self-assembly strategy, based on the results outlined above, allows the creation of a fully functionalized, cross-linked systems. Simultaneous addition of a small metal-complexing molecule such as pyridine, along with a hydrogen-bonding cross-linker such as 

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The solution UV-Vis data for the copolymers 31-33 indicated that increasing the amount of dodecyl side chains increases the solution disorder leading to a non-planar structure [105]. However, in the solid state, the polymers with a higher percentage of dodecyl side chains self-assembled in order to form planar structures with... 

A Joint Experimental/Modeling Methodology Self-Assembly of Homopolymer Chains Influence of the Side Groups Self-Assembly of Copolymers... 

Fig. 3. (a) Chemical stmcture of a synthetic cycHc peptide composed of an alternating sequence of D- and L-amino acids. The side chains of the amino acids have been chosen such that the peripheral functional groups of the dat rings are hydrophobic and allow insertion into Hpid bilayers, (b) Proposed stmcture of a self-assembled transmembrane pore comprised of hydrogen bonded cycHc peptides. The channel is stabilized by hydrogen bonds between the peptide backbones of the individual molecules. These synthetic pores have been demonstrated to form ion channels in Hpid bilayers (71). 

FIG. 1 Self-assembled structures in amphiphilic systems micellar structures (a) and (b) exist in aqueous solution as well as in ternary oil/water/amphiphile mixtures. In the latter case, they are swollen by the oil on the hydrophobic (tail) side. Monolayers (c) separate water from oil domains in ternary systems. Lipids in water tend to form bilayers (d) rather than micelles, since their hydrophobic block (two chains) is so compact and bulky, compared to the head group, that they cannot easily pack into a sphere [4]. At small concentrations, bilayers often close up to form vesicles (e). Some surfactants also form cyhndrical (wormlike) micelles (not shown). 

To be successful in these applications, it is important that materials can self-assemble into precisely defined structures. Peptide-based polymers have many advantages over conventional synthetic polymers since they are able to hierarchically assemble into stable, ordered conformations [4]. Depending on the substituents of the amino acid side chain, polypeptides are able to adopt a multitude of... 

Peptide Synthesis and Self-Assembly Table 1 Common side-chain protecting groups... 

The coacervation of tropoelastin plays a crucial role in the assembly into elastic fibers. This coacervation is based on the LCST behavior of tropoelastin, which causes tropoelastins structure to become ordered upon raising the temperature. The loss of entropy of the biopolymer is compensated by the release of water from its chain [2, 18, 19]. This release of water results in dehydration of the hydrophobic side chains, and this is the onset of the self-assembly leading to the alignment of tropoelastin molecules. 

Fig. 3. An idealized representation of the supramolecular cylinder self-assembled from a single chain of the dendrimer derived from monomer 9 (R=OC12H25, n=3) in the hexagonal columnar phase, assuming one single backbone per cylinder, drawn to proportion with existing experimental data a tilted side view b top view. Reproduced with permission from references 5 a...

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