Polymer systems comparisons with molecular simulation

The above molecular thermodynamic model for polymer systems has been widely tested by comparing with simulation results (Yang et al., 2006a Xin et al., 2008a). Figure 8 shows the comparisons between predicted critical temperature and critical volume fraction for binary polymer solutions at different chain lengths of with the... 

Abstract This chapter discusses the potential of fluorescence correlation spectroscopy (PCS) to study polymer systems. It introduces the technique and its variations, describes analysis methods, points out advantages and limitations, and summarizes PCS studies of molecular and macromolecular probes in polymer solutions, polymer gels, polymer nanoparticles, and polymeric micellar systems. In addition, a comparison with other experimental methods is presented and the potential of a combination with simulations discussed. 

One should also add that there are a lot of attempts to quantify the polymer properties, using computer simulations (Monte Carlo and molecular dynamics), that is, to provide information on the time evolution of a system as well as its time-averaged properties. Although some question still remains as to the validity of these studies, mainly because of the very short duration of simulation in comparison with laboratory experiments, they have nonetheless foimd widespread use and provided many usefiil insights into the nature of the glassy state. It should be a subject of a special review. 

Modeling of polymer membrane structure through dynamics simulations is generally coupled with the water/proton-transfer properties. Yana et al. conducted molecular dynamics (MD) simulations of Krytox-Silica-Nafion composite membranes in comparison to the pure Nation. A 5 wt% of carboxylic acid terminated perfluoropolyether hybrid with silica (Krytox-Silica) in Nation composite polymer was used in the modification of a PEM in order to improve its efficiency at high operating temperatures. MD simulations were carried out in order to understand the microscopic properties of two systems, Krytox-Silica in Nation and pure... 

The previous sections indicate the ability of chemically detailed simulations to explain experimental data and the potential for predictions in unknown systems. All-atomic simulation often bridges the gap between indirect structural information obtained from spectroscopic, thermal, and mechanical measurements and molecular level details. The local dynamics of polymer chains [193] agrees with C-H NMR relaxation data on a relative scale [2] however, absolute correlation times in the simulation appear to be 2.5 times the real value. This mismatch could be associated with overestimated torsion barriers in atomistic models, such as an eclipsed barrier of 5-6kcalmol for n-butane (from ab initio calculations) in comparison to the experimental value of 4.0 kcal mol [228] such differences can... 

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