Molecules Macromolecules Single-molecule

Any extended part of a linear polymer molecule exhibits a strong anisotropy of many properties since its atoms and atomic groups are oriented and the macromolecule is actually a one-dimensional crystal . The parallel packing of these parts during the formation of a uniaxially oriented polymer substance imparts the anisotropie properties of a single molecule to the whole polymeric material. 

P. Kumar, A. Mehta, S.M. Mahurin, S. Dai, M.D. Dadmun, B.G. Sumpter, and M.D. Barnes, Formation of oriented nanostructures from single molecules of conjugated polymers in microdroplets of solution the role of solvent, Macromolecules, 37 6132-6140, 2004. 

Keywords. Hyperbranched macromolecules. Polymer films. Scanning force microscopy. Conformational transitions and interfacial ordering of single molecules... 

The occurrence of the l.c. state of low molar mass substances is, as described, always related to a defined chemical constitution. The idea is obvious to tie up the mesogenic molecules to a macromolecule by a suitable chemical reaction. Assuming the mesogenic structure of the single molecules is uncharged by polymerization and can be found in the monomer unit of the polymer, it can be expected that the macro-molecules also exhibit the l.c. state. 

Zhang W, Zhang X (2003) Single molecule mechanochemistry of macromolecules. Progress in Polymer Science 28(8) 1271-1295... 

Fig. 7 Approaches for linking macromolecules to solid surfaces using biotin-strept(avidin) systems. Either biotin or streptavidin may be directly linked to a surface (e.g. Fig. 6). There are a large number of biotin derivatives with different spacer arms (e.g. Fig. 3) that may be used for immobilization. The choice of a specific biotin depends on which active group occurs on the native or derivatized surface. Attachment of strept(avidin) may be done with methods used with other proteins. Note that the deposition of a biotinylated molecules to a surface may also be used (e.g. biotinylated small molecules or large molecules like BSA) to link strept(avidin) to a surface. A DNA covalently attached at one end (3 end) can have a functional biotin at the other end that could bind to strept(avidin) or be covalently linked to streptavidin (see Fig. 4). Single-stranded DNA bound to immobilized streptavidin is available for hybridization to its complementary sequence (See Fig. 4)...

Dalhaimer P, Bates FS et al (2003) Single molecule visualization of stable, stiffness-tunable, flow-conforming worm micelles. Macromolecules 36 6873-6877... 

Hugel, T., Grosholz, M., Clausen-Schaumann, H., Pfau, A., Gaub, H., and Seitz, M. (2001). Elasticity of single polyelectrolyte chains and their adsorption from solid supports studied by AFM based single molecule force spectroscopy. Macromolecules, 34, 1039-1047. 

For both linear and star polymers, the above-described theories assume the motion of a single molecule in a frozen system. In polymers melts, it has been shown, essentially from the study of binary blends, that a self-consistent treatment of the relaxation is required. This leads to the concepts of "constraint release" whereby a loss of segmental orientation is permitted by the motion of surrounding species. Retraction (for linear and star polymers) as well as reptation may induce constraint release [16,17,18]. In the homopol5mier case, the main effect is to decrease the relaxation times by roughly a factor of 1.5 (xb) or 2 (xq). In the case of star polymers, the factor v is also decreased [15]. These effects are extensively discussed in other chapters of this book especially for binary mixtures. In our work, we have assumed that their influence would be of second order compared to the relaxation processes themselves. However, they may contribute to an unexpected relaxation of parts of macromolecules which are assumed not to be reached by relaxation motions (central parts of linear chains or branch point in star polymers). 

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