  Coarse-grained theories of dense polymer liquids such as block copolymer
melts predict a universal dependence of equilibrium properties on a few
dimensionless parameters. For symmetric diblock copolymer melts, such theories
predict a universal dependence on only chi N and Nbar, where chi is an
effective interaction parameter, N is a degree of polymerization, and Nbar is a
measure of overlap. We test whether simulation results for the structure factor
S(q) obtained from several different simulation models are consistent with this
two-parameter scaling hypothesis. We compare results from three models: (1) a
lattice Monte Carlo model, the bond-fluctuation model, (2) a bead-spring model
with harsh repulsive interactions, similar to that of Kremer and Grest, and (3)
a bead-spring model with very soft repulsion between beads, and strongly
overlapping beads. We compare results from pairs of simulations of different
models that have been designed to have matched values of Nbar, over a range of
values of chi N and N, and devise methods to test the scaling hypothesis
without relying on any prediction for how the phenomenological interaction
parameter chi depends on more microscopic parameters. The results strongly
support the scaling hypothesis, even for rather short chains, confirming that
it is indeed possible to give an accurate universal description of simulation
models that differ in many details.
