Calculation of the van der Waals potential energy for polyethylene and polytetrafluoroethylene as two-atom and three-atom chains: rotational freedom in the crystals

The van der Waals potential energy of polyethylene [9002-88-4] and polytetrafluoroethylene [9002-84-0], computed as a function of both 2 and 3 angles of rotation around the bonds of the backbone chain, showed more minima than predicted by the equivalence principle. The van der Waals potential energy in PTFE crystals, rotating the polymer chains around their helical axes in phase, indicated that the macromols. were free-rotating