Atomistic simulation quantitative structure property

Finally, it is highly desirable to improve the ability to calculate the properties of surfaces and interfaces involving polymers by means of fully atomistic simulations. Such simulations can, potentially, account for much finer details of the chemical structure of a surface than can be expected from simulations on a coarser scale. It is, currently, difficult to obtain quantitatively accurate surface tensions and interfacial tensions for polymers (perhaps with the exception of flexible, saturated hydrocarbon polymers) from atomistic simulations, because of the limitations on the accessible time and length scales [49-51]. It is already possible, however, to obtain very useful qualitative insights as well as predictions of relative trends for problems as complex as the strength and the molecular mechanisms of adhesion of crosslinked epoxy resins [52], Gradual improvements towards quantitative accuracy can also be anticipated in the future. 

The best-known physically robust method for calculating the conformational properties of polymer chains is Rory s rotational isomeric state (RIS) theory. RIS has been applied to many polymers over several decades. See Honeycutt [12] for a concise recent review. However, there are technical difficulties preventing the routine and easy application of RIS in a reliable manner to polymers with complex repeat unit structures, and especially to polymers containing rings along the chain backbone. As techniques for the atomistic simulation of polymers have evolved, the calculation of conformational properties by atomistic simulations has become an attractive and increasingly feasible alternative. The RIS Metropolis Monte Carlo method of Honeycutt [13] (see Bicerano et al [14,15] for some applications) enables the direct estimation of Coo, lp and Rg via atomistic simulations. It also calculates a value for [r ] indirectly, as a "derived" property, in terms of the properties which it estimates directly. These calculated values are useful as semi-quantitative predictors of the actual [rj] of a polymer, subject to the limitation that they only take the effects of intrinsic chain stiffness into account but neglect the possible (and often relatively secondary) effects of the polymer-solvent interactions. 

Pair-additive interactions continued to be used in most materials-related simulations for over 20 years after Vineyard s work despite well-known deficiencies in their ability to model surface and bulk properties of most materials. Quantitative simulation of materials properties was therefore very limited. A breakthrough in materials-related atomistic simulation occurred in the 1980s, however, with the development of several many-body analytic potential energy functions that allow accurate quantitative predictions of structures and dynamics of materials.These methods demonstrated that even relatively simple analytic interatomic potential functions can capture many of the details of chemical bonding, provided the functional form is carefully derived from sound physical principles. 

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