Structure formation of a quenched single polyethylene chain with different force fields in united atom molecular dynamics simulations

Abstract

The differences in the structure formations of a single polyethylene (PE) chain in united atom molecular dynamics (UAMD) simulations under quenching was investigated with varying force fields (FFs) that included torsional potential. We estimated the crystallinity of the folded structures undergoing local crystallization of the single PE chain. In simulations with DREIDING FF, highly folded structures were observed with fast quenching at the rate of 50 K/ns. From the viewpoint of crystallinity, we clarified that it was easy to achieve folding of the PE chains into local crystals with DREIDING FFs. With recent commonly used general FFs such as OPLS-UA and TraPPE-UA, highly folded structures were observed by quenching at the rate of 1 K/5 ns. In the present paper, we examine the Rigby–Roe (RR) FF optimized by Theodorou and coworkers and Paul–Yoon–Smith (PYS) FF optimized by Rutledge and coworkers. With the RR-Theodorou and PYS-Rutledge FFs, crystallization was observed with quenching at 1 K/ns and 1 K/5 ns, respectively. Consequently, it was relatively easier to achieve folding with the RR-Theodorou FF than with the PYS-Rutledge, OPLS-UA, and TraPPE-UA FFs.