Molecular dynamics simulations of structural formation of a single polymer chain: Bond-orientational order and conformational defects

The structural formation of a single polymer chain with $500$ CH${}_2$ groups is studied by the molecular dynamics simulations. Our simulations show that the bond-orientationally ordered structure at low temperatures is formed from a random-coil structure at high temperatures by a gradual stepwise cooling. From the radii of gyration and the bond-orientational order parameters, it is found that the anisotropy of a polymer chain also grows during the growth of the bond-orientational order. In the bond-orientationally ordered structure at low temperatures, $16$ stems form a structure with deformed hexagonal symmetry and the stems in the outer layer have a tilted configuration. Furthermore, the gauche states are localized in the fold surface and the conformational states in the fold surface change more readily than those in the orientationally-ordered region.