Rotational isomeric state models

Each of these — 2 torsion angles can be in one of three states (t, g +, g - ) and therefore the whole chain has 3 rotational isomeric states. For example, w-pentane, with n — A main-chain bonds and n —2 = 2 torsion angles, has 3=9 rotational isomeric states  

In the rotational isomeric state model, these states are not equally probable. Correlations between neighbouring torsional states are included in the model. For example, a consecutive sequence of g+ and g has high energy due to overlap between atoms and therefore is taken to have very low probability in the rotational isomeric state model. The relative probabilities of the states of neighboring torsional angles are used to calculate the mean-square end-to-end distance and C o [Eq. (2.12)]. 

Bond length / Fixed Fixed Fixed Fixed 

Bond angle 9 Free Fixed Fixed Fixed 

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Chain models capture the basic elements of the amphiphilic behaviour by retaining details of the molecular architecture. Ben-Shaul et aJ [ ] and others [ ] explored the organization of tlie hydrophobic portion in lipid micelles and bilayers by retaining the confonuational statistics of the hydrocarbon tail withm the RIS (rotational isomeric state) model [4, 5] while representing the hydrophilic/liydrophobic mterface merely by an... 

Rehahn M, Mattice W L and Suter U W 1997 Rotational isomeric state models in macromolecular systems Adv. Polym. Sc/. 131/132... 

Rehahn M, Mattice WL, Suter UW (1997) Rotational isomeric state models in macromolecular systems. In Advances in Polymer Science, Springer, Berlin... 

W.L. Mattice and U.W. Suter, Conformational Theory of Large Molecules The Rotational Isomeric State Model in Macromolecular Systems, Wiley, New York, 1994. 

Rotational Isomeric State Model with Deformation... 

Rehahn, M., Mattice, W. L. and Suter, U. W. Rotational Isomeric State Models in Macro-molecular Systems. Vol. 131/132, pp. 1-475. 

A very common approximation goes by the name of rotational isomeric state model (RIS). With such a model it is assumed that the molecular population is placed exclusively in a few energy minima, always according to the Boltzmann distribution. The conformations corresponding to the minima are called conformers, or rotational isomers, and are indicated by one or more letters (G, T) for butane three conformers are considered (G, T, G ), for pentane five (TT, G T, TG, G G, G G ). A more detailed examination of pentane reveals the existence of two further wells (fl, = 65 , 2 = 260° and 0, = 100°, 02 = 295°), sometimes indicated by G G and G G , respectively, close to the forbidden G G" conformation, but with a much tower energy (157, 158). 

Rotational Isomeric State Models in Macromolecular Systems... 

Mattice WL, Suter UW (1994) Conformational theory of large molecules the rotational isomeric state Model in macromolecular systems. Wiley, New York... 

Mattice WL, Suter UW (1994) Conformational theory of large molecules The rotational isomeric state model in macromolecular systems, Wiley, New York Moritani T, Fujiwara Y (1973) J Chem Phys 59 1175 Nagai KJ (1959) J Chem Phys 31 1169 Nagai KJ (1962) J Chem Phys 37 490 Natta G, Corradini P, Ganis P (1962) J Polym Sci 58 1191 Suter UW (1981) Macromolecules 14 523 Viswanadhan VN, Mattice WL (1987) Macromolecules 20 685 Volkenstein M (1958) J Polym Sci 29 441 Volkenstein MV (1951) Dokl Akad Nauk SSSR 78 879... 

Theoretical and experimental studies have also been carried out on sodium phosphate.48 Theoretical values for molar cyclization constants for the oligomeric molecules were calculated using the rotational isomeric state model. Specifically, calculations... 

Quantitative determination of conformational disorder, in addition to assignments of the spectral features, requires accurate calibrations of relative absorptivities (extinction coefficients) for the various bands. These were calculated with the aid of the rotational isomeric state model of Flory (22), a statistical mechanical determination of conformational disorder in alkanes. The model requires an estimate for the energies of gauche bonds, chosen from the best available experiments to be 508 +/- 50 cal/mole, and an energy for the bond pairs E, chosen to be 3000 cal/mole. The... 

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