Second virial coefficients of Lennard–Jones chains

The second virial coefficients B2 of Lennard–Jones chain fluids were calculated through Monte Carlo integration as a function of chain length m (up to 48 segments) and temperature. We found that at a fixed temperature the second virial coefficient decreases with chain length. At low temperatures, the virial coefficient changes sign from positive to negative as m increases. The simulation data also provide an estimate for the theta temperature TΘ at which the attractive and repulsive interactions cancel each other for dilute solutions. It is found that the theta temperature TΘ for Lennard–Jones chains with m>32 is 4.65 independent of chain length m. A comparison of simulated values of B2 with those evaluated from two different perturbation theories for chain fluid shows that these approximate theories underestimate the second virial coefficients of Lennard–Jones chains.