  With the help of a simple two-dimensional model we simulate the tribological
properties of a thin lubricant film consisting of linear (chain) molecules in
the ordinary soft-lubricant regime. We find that friction generally increases
with chain length, in agreement with their larger bulk viscosity. When
comparing the tribological properties of molecules which stick bodily to the
substrates with others carrying a single sticking termination, we find that the
latter generally yield a larger friction than the former.
