The static and dynamics behavior of the cis-1,4-polyisoprene during the glass transition is closely related to its macroscopic property, which will be significantly affected by the external pressure. Therefore, here an all-atom molecular dynamics simulation is performed to systemically investigate the effect of the pressure (P?=?1?2000?atm) on the glass transition temperature (Tg) for cis-1,4-polyisoprene, which is dependent on the static and dynamic properties. For the static property, the polymer density and the energy are considered. It is found that the polymer density, the non-bond energy and the torsional energy play an important role during the glass transition process. Meanwhile, the Tg obtained from the non-bond energy and the torsional energy is larger than that from the polymer density. For the dynamic property, the translational mobility, the bond reorientation mobility, the torsional dynamics and the dynamic heterogeneity on the chain backbone are analyzed. The mobility on the chain backbone decreases with increasing the pressure, which gradually increases the Tg. In addition, the Tg obtained from the dynamic heterogeneity is largest compared to those from the bond reorientation mobility, the torsional dynamics or the atom translational mobility. Especially, according to the mean-square fluctuations of the backbone atoms, the immobile atoms are distinguished. Then, the percolation probability of the immobile domain is analyzed, which is further characterized by the size of the largest immobile domain and the number of the immobile domains. By observing the snapshot of the mean-square fluctuations of atoms, the percolation transition of the immobile domains is clearly observed, which can help to understand the glass transition process under the different pressures.

» Author: Wei Sun, Haoyu Wu, Yanlong Luo, Bin Li, Lixin Mao, Xiuying Zhao, Liqun Zhang, Yangyang Gao

» Publication Date: 03/01/2022

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