The geometries and conformational energies of model segments of poly (vinyl fluoride) (PVF) are obtained from quantum chemistry calculations and used to determine the statistical weight parameters in a rotational isomeric state (RIS) model. The interaction energies show that the electrostatic interaction is important in the molecules containing high electronegative atoms, The calculated characteristic ratio is in agreement with available theoretical values by means of molecular mechanics (MM). (c) 2005 Elsevier B.V. All rights reserved.