Polymer chain, rigidity

Nanostructures primarily result from polyelectrolyte or interpolyelectrolyte complexes (PEC). The PEC (also referred to as symplex [23]) is formed by the electrostatic interaction of oppositely charged polyelectrolytes (PE) in solution. The formation of PEC is governed by physical and chemical characteristics of the precursors, the environment where they react, and the technique used to introduce the reactants. Thus, the strength and location of ionic sites, polymer chain rigidity and precursor geometries, pH, temperature, solvent type, ionic strength, mixing intensity and other controllable factors will affect the PEC product. Three different types of PEC have been prepared in water [40] (1) soluble PEC (2) colloidal PEC systems, and (3) two-phase systems of supernatant liquid and phase-separated PEC. These three systems are respectively characterized as ... 

There is one more indirect method of values A correctness checking within the framework of fractal analysis. As it is known through Ref. [5], enhancement of the polymer chain rigidity, characterized by A increase, is accompanied by the exponent growth in Mark-Kuhn-Houwink equation. As it follows from the Eq. (4), reduction at increase should be expected and, hence, A growth. 

As it has been noted above, the value A is often used as a polymer chain rigidity measure. A macromolecular coil in diluted solution is the fractal and its stmcture can be characterized by the fractal dimension The larger is the more compact coil structure is. It is obvious, that the more rigid a pol mer chain is, the more difficult it is to make compact of... 

Let us note one more important aspect. The Eqs. (54) and (55) comparison allows to give one more definition of flexible- and rigid-chain polymers. The indicated equations suppose, that the greatest values of macromolecular coil fiactal dimension are equal to 2.0 (i.e., a coil in ideal 0-solvent [10]) for flexible-chain polymers and 1.667 (i.e., a coil in good solvent [10])—for rigid-chain ones. Hence, such polymers, chain rigidity of which (intramolecular interactions) allows to compensate it by... 

Thus, the results obtained above confirmed the intercommunication of polymer chain rigidity and macromolecular coil in solution structure. The well-known classification of pol5miers (flexible- and rigid-chain ones) is confirmed also and new criteria of such division ate received. 

However, besides the indicated factors, that is, A6 and C, the other parameters can influence on value. In Fig. 32, the dependence Dy(Ad) for polyarylates PD and PF is adduced. As one can see, this dependence breaks down into two curves, in addition one from them includes PAr with rigid para-connections in the main chain (the polyarylates PF-2 and PF-7, Table 5, p. 120 in Ref. [5]) and the other—polyarylates with less rigid metha-connections. The indicated plot demonstrates again the importance of such characteristic as polymer chain rigidity for determination of value of macromolecular coil in solution. 

Dolbrn, I. V. Kozlov, G. V. The intercommunication of polymer chain rigidity and macromolecular coil structure in diluted solutions. Proceedings of All-Russian Sci. Conf Perspective-2003. V. 4. NaTchik, KBSU, 2003, 108-111. 

The Mark-Houwink exponent of 1.8 indicates the high polymer chain rigidity. The persistence length of cis-PBO in MSA reported about 20-30 nm [62] and 50 nm ], whereas the theoretical persistence calculated in the range of 22-65 nm [64-66]. By comparison, the persistence length of flexible polymers such as PE is much shorter (1 nm or less). 

Aramid is the name given to a class of polymers that are aromatic polyamides. The definition of an aramid fiber is a manufactured fiber in which the fiber forming substance is along chain synthetic polyamide in which at least 85% of the amide linkages are attached directly to two aromatic rings . There are various aramid fibers, including poly-m-phenylene isophthalamide known for its flame resistant characteristics (Dupont Nomex ). A second aramid is poly-p-phenylene terephthalamide developed by Akzo and DuPont, which consists of oriented para-substituted aromatic units. This makes polymer chains rigid and rodlike. 

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