Molecular modelling of polymers, 1. Prediction of critical values of oligomethylenes

Most procedures for the estimation of critical values of oligomethylenes assume these critical values to depend only on the chain length n and/or the molecular weight M . In this work, we introduce new equations for estimating the critical values by inclusion of quantum chemical data calculated by a semiempirical SCF‐MO SCF‐MO: Self‐consistent field, molecular orbital. method (AM1). These models give a much superior prediction for the critical values such as the normal boiling point T b , critical temperature T c , critical pressure P c , critical valume V c , surface tension y b and enthalpy of vaporization Δ H vp of 18 oligomethylenes. The predictions for polyethylene (with infinite chain length) for the values of T b , T c , P c , V c , Δ H vp and y b are 1029.3 K, 1029.3 K, 1.013 bar, 15723.3 m 3 /mol, 0 KJ/mol and 0 mN/m, respectively.