Polymers rotational isomeric state

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

The rotational isomeric state (RIS) model assumes that conformational angles can take only certain values. It can be used to generate trial conformations, for which energies can be computed using molecular mechanics. This assumption is physically reasonable while allowing statistical averages to be computed easily. This model is used to derive simple analytic equations that predict polymer properties based on a few values, such as the preferred angle... 

RIS (rotational isomeric state) a polymer simulation technique... 

A suitable approach to the equilibration of an amorphous polymer system at bulk density becomes much more likely when the fully atomistic model in continuous space is replaced by an equivalent coarse-grained model on a lattice with sufficient conformational flexibility. Different strategies, which seek results at different levels of detail, can be employed to create an appropriate coarse-grained model. Section 4 (Doruker, Mattice) describes an approach which attempts to retain a connection with the covalent bonds in the polymer. The rotational isomeric state (RIS) [35,36] model for the chain is mapped into... 

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

Experimental and theoretical results are presented for four nonlinear electrooptic and dielectric effects, as they pertain to flexible polymers. They are the Kerr effect, electric field induced light scattering, dielectric saturation and electric field induced second harmonic generation. We show the relationship between the dipole moment, polarizability, hyperpolarizability, the conformation of the polymer and these electrooptic and dielectric effects. We find that these effects are very sensitive to the details of polymer structure such as the rotational isomeric states, tacticity, and in the case of a copolymer, the comonomer composition. 

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... 

A general theory is presented on the effect of elongation of a polymer chain on the apportionment of its bonds and bond sequences among various rotational Isomeric states. Numerical calculations are presented for PE chains and for syndiotactlc vinyl polymers. 

A molecular dynamics trajectory is computed for methyl-terminated PIB at 400 K. Several time-dependent properties (mean-square end-to-end distance, averaged bond angles, and the number and locations of rotational isomeric states) deduced from the trajectory are in reasonable agreement with the results of earlier experiments and earlier theoretical investigations of the static properties of this polymer. 

W AXS-pattern of a polymer melt if these Boltzmann-weighted distance fluctuations are not accounted for. They characterize a relevant feature of polymer melt structures. We treat this in terms of the Rotational Isomeric State Approximation (RISA) discussed in the next section. 

In a typical analysis of a polymer chain, the experimental values of configuration-dependent properties and their temperature coefficients are compared with the results of rotational isomeric state calculations. These comparisons yield values of the energies for the various rotational states about the backbone bonds, and these conformational preferences can then be used to predict other configuration-dependent properties of the chains. It is also possible to obtain such conformational information from potential energy calculations, using the methods of molecular mechanics.39,46 52... 

The results from the 6-3IG basis set are close to what is observed experimentally. Calculations like these are valuable for molecular mechanics simulations because they provide high quality input data for polymer fragments. In addition, rotational isomeric state and atomistic Monte Carlo simulations of single isolated chains benefit greatly from accurate data derived from quantum mechanical calculations. 

I. Bahar and B. Erman, Macromolecules, 20, 1368 (1987). Investigation of Local Motions in Polymers by the Dynamic Rotational Isomeric State Model. 

Using these ideas. Miller (1978) has given a simple explanation for the validity of the VFTH equation using a rotational isomeric state (RIS) model for polymers, which also provides a molecular interpretation of its parameters, A and Tp. Miller assumes that... 

Figure 4 Cartoon for hidden liquid-liquid spinodal in a polymer melt, calculated for a Flory Rotational Isomeric State chain with a simple coupling between density and conformational order A is the trans-gauche energy gap and a dimensionless density. Shown is the path of an isochoric quence into the unstable regime. r, is the spinodal temperature, T the melting temperature, T the liquid-liquid critical point, and Tp the temperature at which the harrier between dense liquid and crystal is of order ksT ...

In the development of atomistic polymer models some of the milestones were Flory s rotational isomeric state (RIS) model and the development of force field simulations of polymers which led to, and have been significantly developed in the context of commercial molecular modelling software. 

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