EQUATION OF STATE OF 2-DIMENSIONAL LATTICE CHAINS AT THE THETA POINT

Systems of two-dimensional lattice self-avoiding walks with nearest-neighbor attractive interactions are studied in Monte Carlo simulations, focusing on the theta-point, where the second virial coefficient vanishes. The equation of state is determined for the first time, for chains of 40 and 80 segments over a wide range of densities. The results are consistent with des Cloizeaux' scaling law, and yield a value for the tricritical exponent nu(t)0.57 (3), in close agreement with recent estimates. The simulations also provide information on the the density profile at a wall, and on the variation of chain dimensions with density at the theta-point.