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

1 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 ΔH_vp of 18 oligomethylenes. The predictions for polyethylene (with infinite chain length) for the values of T_b, T_c, P_c, V_c, ΔH_vp and y_b are 1029.3 K, 1029.3 K, 1.013 bar, 15723.3 m³/mol, 0 KJ/mol and 0 mN/m, respectively.