Conformation semi-dilute solution

However, let note, that the assumption about independence of the osmotic pressure of semi-diluted solutions on the length of a chain is not physically definitely well-founded per se it is equivalent to position that the system of strongly intertwined chains is thermodynamically equivalent to the system of gaped monomeric links of the same concentration. Therefore, both Flory-Huggins method and Scaling method do not take into account the conformation constituent of free energy of polymeric chains. 

In that way, the thermodynamic approach with the use of conformational term of chemical potential of macromolecules permitted to obtain the expressions for osmotic pressure of semi-diluted and concentrated solutions in more general form than proposed ones in the methods of self-consistent field and scaling. It was shown, that only the osmotic pressure of semi-diluted solutions does not depend on free energy of the macromolecules conformation whereas the contribution of the last one into the osmotic pressure of semi-diluted and concentrated solutions is prelevant. 

J. Ren, O, Urakawa, K, Adachi, Dielectric study on dynamics and conformation of poly(D,L-lactic acid) in dilute and semi-dilute solutions. Polymer 2003, 44, 847-855. 

In what kind of conformational state are polymers in a (i) good solvent, dilute solution (ii) theta solvent, dilute solution (iii) good solvent, semi-dilute solution (iv) molten state ... 

Thanks to the newly built neutron large-scale facilities, successes in polymer science were immediate in the mid-1970s [9]. Neutron scattering experiments gave the first direct confirmation of the Gaussian behavior of polymer chains in the solid state as was predicted earlier by Flory [10]. They further revealed the chain conformation in semi-dilute solutions, which confirmed the relevancy of extending scaling... 

In this work, an experimental study was conducted on gelatin in semi-dilute region in water solution and research the effect of temperature, pH, zeta potential, and ionic strength on hydrodynamic properties by viscometiy, in order to determine the conformational characteristic, and phase transition (Tgei). 

That fact the scaling method and presented thermodynamic approach from seeming opposite positions lead to practically the same result in the form (8) and (35) can be named as mysterious incident if it were not two circumstances. First is exactly free energy of the conformation makes the main contribution into the osmotic pressure of the semi-diluted and concentrated solutions. The second is the peculiarity of the point c = c. ... 

A coirplete understanding of the role of carbohydrates in biological systems requires knowledge of the distribution at equilibrium of the various conformers in aqueous solution. The conformational behavior of carbohydrates in solution can be examined from different vantage points (1,), but the most relevant approach is, no doubt, study of dilute solutions themselves. At present, high resolution NMR spectroscopy is the primary tool for determination of three-dimensional structure of oligosaccharides in solution. Optical rotation is also very sensitive to conformation (2) and there is a new, semi-enqpirical theory of optical rotation of oligosaccharides ( ). 

The conformation parameter a (=A/Af, where Af is A of a hypothetical chain with free internal rotation) for cellulose and its derivatives lies between 2.8-7.5 2 119,120) and the characteristic ratio ( = A2Mb//2, where Ax is the asymptotic value of A at infinite molecular weight, Mb is the mean molecular weight per skeletal bond, and / the mean bond length) is in the range 19-115. These unexpectedly large values of a and Cffi suggest that the molecules of cellulose and its derivatives behave as semi-flexible or even inflexible chains. For inflexible polymers, analysis of dilute solution properties by the pearl necklace model becomes theoretically inadequate. Thus, the applicability of this model to cellulose and its derivatives in solution should be carefully examined. 

The SARW statistics of linear pol5mieric chain into diluted solution determines [72] the density of distribution to which corresponds the probability cc X)Ti d/i i = 1, <7 of that the SARW trajectory by its last step hits into the volume of the elementary layer R n,dA, on the surface of the equilibrium conformational ellipsoid with the semi-axes s X. = R, ., in a form... 

Many other semi-flexible polymers are known which can be reasonably well modeled on wormlike chains. The Ml values obtained for most of such polymers are close to those calculated from crystallographic data, suggesting that stiff polymers in dilute solution maintain their crystalline conformations at least locally. 

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