They possess high density and long range order.
They do not possess isotropy, and therefore are anisotropic in nature, which means they show anisotropy and limited conformation space.
However, just as atomic crystals have lattices, polymer crystals also exhibit a periodic structure called a lattice, which describes the repetition of the unit cells in the space.
The simulation of polymer crystals is complex and not taken from only one state but from solid-state and fluid-state physics as well.
It is especially important in polymer crystals to be cognizant of the limitations imposed by either the assumptions on which a method is based or the robustness of the simulation method.