Helical supramolecular polymers

As mentioned above, 3-p- BocCiNH-a-CD forms helical supramolecular polymers in aqueous solutions. In contrast, 6-p- BocCiNH-) -CD was synthesized and found to form an intramolecular complex using NMR measurements. When adamanta-necarboxylic acid (1-AdCA) was added as a competitive guest to an aqueous solution of 6-p- BocCiNH- -CD, NMR spectra showed that the Boc-cinnamamide part in its own fi-CD cavity was expelled into water. The 6-p- BocCiNH- -CD underwent a conformational change to form an inclusion complex with AdCx. Moreover, with an addition of an excess amount of a-CD, the cinnamoyl part was found to be included in a-CD to form a hetero dimer (Fig. 3.27). 

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Brunsveld L, Vekemans JAJM, Hirschberg JHKK, Sijbesma RP, Meijer EW. Hierarchical formation of helical supramolecular polymers via stacking of hydrogen-bonded pairs in water. Proc Natl Acad Sci USA 2002 99 4977-4982. 

Van Gestel J (2004) Amplification of chirality in helical supramolecular polymers. The majority-rules principle. Macromolecules 37 3894—3898... 

Fig. 23 A proposed structure of a helical supramolecular polymer formed by 3-p- BocCiNH-a-CD in aqueous solution...

BocCiNH-a-CD was found to be incorporated into the CD cavity of an adjacent monomer in a slantwise state. The substitutions were found to exist as a left handed-anti-configuration. The formation of a helical supramolecular polymer with some cooperativity is shown by the increasing intensities of Cotton effect peaks with increase in the concentrations. Fig. 3.25 shows an STM image of the... 

R. Sun, X. Ma, M. Gao, H. Tian, Q. Li, Light-driven linear helical supramolecular polymer formed by molecular-recognition-directed self-assembly of bis-p-sulfonatocalix[4]arene and pseudorotaxane. J. Am. Chem. Soc. 135, 5990-5993 (2013)... 

Rowan and Nolte helical supramolecular polymers from self-assembly... 

The racemic mixture of all four components LP2, LU2, DP2, and DU2 yielded long superhelices of opposite handedness that coexisted in the same sample, pointing to the occurrence of spontaneous resolution through chiral selection in molecular recognition-directed self-assembly of supramolecular liquid-crystalline polymers. Such chiral selection features of self-organized entities are of general significance in connection with the questions of spontaneous resolution and of chirality amplification. This was confirmed by subsequent studies on a variety of helical supramolecular polymers (see Chapters 2, 3, and 6). 

For Co > C the second term in Eq. (11) increases with Co and all excess units form helical supramolecular polymers coexisting with monomers and short linear sequences having constant concentration C. The average DP of the helical polymer... 

J. van Geslel. Theory of Helical Supramolecular Polymers. PhD Thesis, Eindhoven Universily of Technology, 2003. 

For a further discussion of helical supramolecular polymers see Chapters 2 and 3. 

There is no definite evidence of synthetic supramolecular polymers able to produce the extremely large DP achieved in the helical polymerization of biological systems. The polymer in Fig. 2B has been reported to display a triple helical structure in the solid state [9]. However, occurrence of large DP in isotropic solution was not reported. The H-bonded assembly involving pimelic acid and bis-2-aminopyridine has been suggested to exhibit helical structure in both sohd state and diluted solutions ([137] cf. also this volume, Chapter 4). Guidehnes for future attempts to synthesize helical supramolecular polymers stable even in... 

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