  We study the mutual interactions of simple, parallel polymers and nanotubes,
and develop a scheme to include the van der Waals interactions in the framework
of density functional theory (DFT) for these molecules at intermediate to
long-range separations. We primarily focus on the polymers polyethylene,
isotactic polypropylene, and isotactic polyvinylchloride, but our approach
applies more generally to all simple polymers and nanotubes. From
first-principle DFT calculations we extract the electron density of the
polymers and their static electric response. We derive explicit expressions for
the van der Waals interaction energy under simple symmetry assumptions.
