Structure formation of a single polymer chain in solution: A molecular dynamics study

Molecular dynamics simulations are carried out to study the structure formation of a single polymer chain in solution. A random conformation of a polymer chain in solution at high temperature (550K) is quenched to several lower temperatures (300, 350, and 400K). Our simulations show the following characteristics: 1) At lower quenching temperature (300K), local orientationally ordered domains are formed first, and they grow to be a folded orientationally ordered structure. 2) At a higher quenching temperature (400K), a toroidal structure can be formed. 3) At an intermediate quenching temperature (350K), a toroidal structure can be formed before a folded orientationally ordered structure is formed. The last characteristic indicates that an intermediate toroidal structure at 350K is in a metastable state. We also find that it depends on the initial conformation of a polymer chain, whether a toroidal structure is formed or not.