Molecular Dynamics Studies on Pressure-Induced Structural Change of Poly(4-methyl-1-pentene) Melts

K Hagita and Y Senda, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 87, 114803 (2018).

DOI: 10.7566/JPSJ.87.114803

Pressure-induced structural changes of the intermediate-range order in poly(4-methyl-1-pentene) melts were examined by united atom molecular dynamics (UAMD) simulations. Here, a modification of coarse graining to united atoms (UA) for the DREIDING force fields (FFs) was considered from the viewpoints of macromolecules and compared with stateof- the-art FFs such as TraPPE-UA and OPLS-UA. We confirmed that the behaviors of the peak positions of the first sharp diffraction peak (FSDP) and second peak were in good agreement with the results of the experiments by Chiba et al. Phys. Rev. E 85, 021807 (2012). TraPPE-UA FF showed better reproduction than the modified DREIDING and OPLS-UA FFs. We concluded that UAMD simulations with the modified DREIDING FF well reproduced a structural property that originated from microscopic structures, although there was a density difference of 1.23 times, which corresponds to a length difference of 1.07 times. To explore the nature of the FSDP, we examined poly-4-isobutyl-6methyl- 1-heptene, which can be recognized as a polymer with dendrimer-like side chains. We clarified that the peak position of the FSDP depends on a size of the side chain group.

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