Special issue on multiscale modeling of polymers

Polymer Science is inherently a multiscale undertaking. We all know that the relevant length scales start at the Angstrom level, for example for hydrogen bonds, and reach to the macroscopic scales of (at least) millimeters. Therefore it comes as no surprise that polymer scientists have out of necessity been traditionally at the forefront of developing multiscale descriptions for their systems. This is especially true in the area of polymer simulations as most meaningful simulations would be impossible if all system details would have to be taken into account; the required computer time would be just of reach. On the other hand the local interactions have a non-negligible influence even for intermediate to large length scales. Thus, descriptions taking care of both of these constraints are needed.

This issue “Multiscale modeling in polymer science and related disciplines” intends to fulfill a two-fold purpose. First, it wants to be a platform for recent advances in computational polymer science by use of novel multiscale simulation techniques. This includes developing new simulation approaches and novel applications of existing ones. Second, it wants to bridge to neighboring disciplines where the techniques developed for polymers may also be useful.

In this issue the reader will find technical advances in multiscale simulations which have the promise to solve future simulation problems. You will also find contributions which actually apply multiscale ideas to address scientific questions we otherwise could not answer. The contributions by Milano et al. and by Helfer et al. on novel mapping techniques for polymers or by Ismail et al. on wavelet analysis are excellent examples of new simulation approaches. The new technique by Tapia-McClung and Jensen is not specifically targeted for polymers but can improve modeling of molecules in general. The work by Sukumaran et al. is actually a very innovative combination of simulation and analysis to approach the long standing question on the nature of chain entanglements. Müller and Smith use a combination of mean-field and multi-chain approaches to address phase separation, a phenomenon which by its very nature is macroscopic but has its roots in the microscopical description.

Systems like block copolymers immediately add an additional length scale to the picture, the block length, which makes them prototype targets for multiscale modeling. The cover picture of this issue comes from the work of Guo and Luijten. It is another excellent example of a complex problem which requires a multiscale approach. It shows the complexity of reversible gel formation in triblock copolymers. The work by Fraser et al. focuses on copolymers as well. They use detailed simulations of self assembly to develop a model of the assemblies. Sliozberg and Abrams add another degree of complexity to the picture, a more complex topology, as they study comb heteropolymers and the effect of solvents on the structure.

Browsing through this issue you will find a wide variety of scales for the description of the problems. There are problems like the bonding of alcohol to phospholipid membranes studied by Dickey where a fully atomistic description is necessary and problems where continuum descriptions are needed like in the example by Shenogin and Ozisik. This study of deformations bridges from an atomic level to a continuum description.

Furthermore, this special issue wants to bridge out to neighboring disciplines of soft-condensed matter where the same or similar approaches can be applied. This cross pollination is something we have to foster as we should not reinvent the wheel but make it going. Nanocomposites are an emerging field where multiscaling is necessary, you will here find two contributions on this field. Borodin et al. discuss the mechanical properties of polymer nanocomposites and Anderson et al. study the intercalation of binary fluid between inorganic sheets. Also the study on phospholipids which make up all cell membranes clearly benefits from ideas developed in polymer coarse graining. Guzman et al. use a novel technique to calculate the free energy of colloids in a nematic liquid crystal. The contribution by Pandey et al. at the end of this issue shows clearly the effect of polymer multiscaling can have on neighboring fields as bond fluctuation Monte Carlo was developed for polymers more than a decade ago and now is used to study model membranes.