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Force field induced heterogeneous molecular orientation within polyacrylonitrile monofilaments.

ABSTRACT: The molecular orientation evolution in the radial direction of PAN precursor fiber is investigated by polarized Raman spectroscopy. Samples with different drawing ratios during the steam stretching process are prepared. The corresponding crystallinity distribution in the cross section is mapped by confocal Raman spectroscopy. Nano-TA is also applied to measure the thermal stability evolution along the radial direction. The results showed that the skin-core difference in terms of molecular orientation became more obvious as drawing ratio increased. The Raman mapping and nano-TA results are also consistent with this trend. Finally, a model is proposed to explain the evolution of chains with increasing drawing ratio.

SUBMITTER: Sha Y

PROVIDER: S-EPMC9086294 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Force field induced heterogeneous molecular orientation within polyacrylonitrile monofilaments.

Sha Yang Y Liu Wei W Wang Mengfan M Wu Jianglu J Cao Weiyu W

RSC advances 20180924 57

The molecular orientation evolution in the radial direction of PAN precursor fiber is investigated by polarized Raman spectroscopy. Samples with different drawing ratios during the steam stretching process are prepared. The corresponding crystallinity distribution in the cross section is mapped by confocal Raman spectroscopy. Nano-TA is also applied to measure the thermal stability evolution along the radial direction. The results showed that the skin-core difference in terms of molecular orient ...[more]

PMID: 35547686

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Project description:BACKGROUND:After the discovery of membrane-reversible electroporation decades ago, the procedure has been used extensively in biology, biotechnology and medicine. The research on the basic mechanism has increasingly attracted attention. Although most research has focused on models that consider all atomic and molecular interactions and much atomic-level information can be obtained, the huge computational demand limits the models to simulations of only a few nanometers on the spatial scale and a few nanoseconds on the time scale. In order to more comprehensively study the reversible electroporation mechanism of phospholipid membrane on the nanoscale and at longer time intervals of up to 100 ns, we developed a dipalmitoylphosphatidylcholine (DPPC) phospholipid membrane model with the coarse-grained Martini force field. The model was tested by separately examining the morphology of the phospholipid membrane, the hydrophilic channel size, the distribution of the voltage potential on both sides of the membrane, and the movement of water molecules and ions during electroporation. RESULTS:The results showed that the process went through several stages: (1) the formation of the pore with defects originating on the surface. (2) The maintenance of the pore. The defects expanded to large pores and the size remains unchanged for several nanoseconds. (3) Pore healing stage due to self-assembly. Phospholipid membrane shrunk and the pore size decreased until completely closed. The pores were not circular in cross-section for most of the time and the potential difference across the membrane decreased dramatically after the pores formed, with almost no restoration of membrane integrity even when the pores started to close. CONCLUSIONS:The mechanism of the reversible electroporation process on the nanoscale level, including defects, expansion, stability, and pore closing stages on a longer time scale of up to 100 ns was demonstrated more comprehensively with the coarse-grained Martini force field, which took both the necessary molecular information and the calculation efficiency into account.

Dataset Information

Force field induced heterogeneous molecular orientation within polyacrylonitrile monofilaments.

Publications

Force field induced heterogeneous molecular orientation within polyacrylonitrile monofilaments.

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