Chain comb-coil

Polushkin E, Alberda van Ekenstein GOR, Knaapila M, Ruokolainen J, Torkkeh M, Serimaa R, Bras W, Dolbnya 1, Ikkala O, ten Brinke G. Intermediate segregation type chain length dependence of the long period of lamellar microdomain structures of supramolecular comb-coil diblocks. Macromolecules 2001 34 4917-4922. 

Fig. 2. Selected architectures of block copolymers (a) diblock (b) triblock (c) comb copolymer consisting of flexible chains (d) rod-coil diblock copolymer consisting of a rodlike block and a coil-like block (e) hairyrods, i.e., comb-block copolymers consisting of rodlike backbone and coil-like side chains and (f) LC coil with a side-chain liquid crystalline (LC) block and a flexible block. Many other variations have been introduced, such as multiblock copolymers, block copolymers consisting of several rodlike blocks, or star-shaped block copolymers. Comb-coil block copolymers with dense packing of side chains are also denoted as molecular bottle brushes, as is illustrated in (g) by a simulated structure of an isolated molecule dissolved in a solvent. (Courtesy of Mika Saariaho.)...

A major difference may exist between HA in vivo and HA chains that are extricated from the in situ situation. Very little is known about the properties of the HA within the narrow confines of the ECM or the restricted volume of the intercellular space. However, when HA undergoes aqueous extraction from major sources, such as from the mucoid layer of the rooster comb, from joint fluid, the perivascular space of the umbilical cord (Wharton s jelly), or from bacterial capsules, the extraction fluid has very high viscoelasticity. Such HA is in a random coil conformation. However, HA is unlikely to be in such a conformation in vivo, and little is known about the state of the HA within tight tissue spaces. It is probably much more structured, and probably has many additional functions that are unknown and lost when examined in vitro [15]. 

Very recently, the self-assembly of poly(y-benzyl-i,-glulamalc)-fo-poly(i,-lysine) rod-coil copolypeptide via ionic complexation was reported by Ikkala, Hadjichristidis and coworkers [65]. Complexation between the anionic surfactants dodecyl benzenesulfonic acid and the cationic poly(L-lysine) chains occurs via proton transfer from the acid group to the base, resulting in electrostatically bonded comb-like structures, and fluid-like liquid crystalline structures at room temperature due to efficient plasticization of dodecyl benzenesulfonic acid. 

The possibilities are not restricted to flexible polymers. One of the blocks can be rigid rodlike, in which case a rod-coil block copolymer [54-57] is formed if the architecture is of the diblock type (see Section 2.3.1 for another example [15]). Other interesting cases comprise diblock copolymers where one of the blocks is a side-chain liquid-crystalline polymer [4, 58-62]. Finally, we mention the important class of hairy rods obtained for a comb copolymer architecture consisting of a rigid backbone and flexible side chains [4, 58-61, 63-66], to be discussed in more depth later in this review. 

Figure 19.23 Schematic diagrams of linear, Y-shaped, and comb-like rod-coil block copolymer brushes. (Reproduced with permission from C.-S. Li, W.-C. Wu, Y.-J. Sheng and W.-C. Chen Effects of chain architectures on the surface structures of conjugated rod-coil block copolymer, Journal of Chemical Physics, 128, 154908, 2008. 2008 American Institute of Physics.)...

A specific feature of the structure of thermotropic comb-shaped macromolecules—the compact structure of the molecular coil and the strongly interacting mesogenic side chains with comparatively low rigidity of the main chain (in comparison to the rigidity of the lyotropic macromolecules examined above, for example)—causes the essential dependence of the intrinsic viscosity on the temperature. 

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