Computation of heat capacities of liquid polymers

The liquid heat capacities at constant pressure of a series of linear polym ers have been computed as the sum of vibrational, external, and conformatio nal contributions. Most of the heat capacity of liquid macromolecules arise s from vibrational motion. The external contribution is assumed to approach zero at constant volume. The conformational contribution, finally, is calc ulated using a fit of experimental heat capacities, as available from the A THAS data bank, to a one-dimensional Ising-type model with two discrete, de generate states. A stiffness and a cooperativity parameter permit the repre sentation of the experimental data for polyethylene, polypropylene, poly(me thyl methacrylate), poly(n-butyl methacrylate), and polystyrene. Agreement between computation and experiment lies within a few percent, close to the experimental precision.