  We report Monte Carlo simulations of the melting of a single-polymer
crystallite. We find that, unlike most atomic and molecular crystals, such
crystallites can be heated appreciably above their melting temperature before
they transform to the disordered "coil" state. The surface of the superheated
crystallite is found to be disordered. The thickness of the disordered layer
increases with superheating. However, the order-disorder transition is not
gradual but sudden. Free-energy calculations reveal the presence of a large
free-energy barrier to melting.
