COMPRESSIBILITY-BASED HARD-SITE MODELS OF LINEAR POLYETHYLENE AND THENORMAL-ALKANES

In the development of an interaction potential for polyethylene, the e ffects of attractions and excluded volume are often difficult to separ ate. Here we consider an experimental quantity which is dominated by t he excluded volume (the compressibility) and require that a hard-site model of polyethylene predict the experimental compressibility. The si te diameter in the model is varied until this requirement is met. We u se a rotational isomeric state model of polyethylene, and the compress ibility of the model is calculated with polymer reference interaction site model (PRISM) theory. The experimental compressibility is found f rom the Olabisi-Simha equation of state. The effects of state variable s and chain length on the site diameter are investigated.