기체 분리용 고분자 분리막의 분자동력학 연구

박치훈,김득주,남상용 한국막학회 2014 멤브레인 Vol.24 No.5

분자 동력학(Molecular dynamics; MD) 전산모사 기술은 대상이 되는 입자(일반적으로, 원자)의 위치와 속도를 계산하여, 원자 및 분자들의 다양한 구조 및 동적 특성을 분석하는 데에 있어서 매우 유용한 기술이다. 기체 분리막 연구에 있어서도 MD는 그동안 free volume 분석, conformation search 등과 같은 고분자 구조 분석 및 permeability, diffusivity와 같은 기체 투과 거동을 연구하는 데 널리 사용되어 왔다. 본 총설에서는 기체 분리막 분야에 MD를 적용하는 일반적인 방법론에 대하여 서술하고, 다양한 관련 연구들을 소개하고자 한다. Molecular dynamics (MD) computer simulation is a very useful tool to calculate the trajectory and velocity of particles (generally, atoms), and thus to analyze the various structures and kinetic properties of atoms and molecules. For gas separation membranes, MD has been widely used for structure analysis of polymers such as free volume analysis and conformation search, and for the study of gas transport behavior such as permeability and diffusivity. In this paper, general methodology how to apply MD on gas separation membranes will be described and various related researches will be introduced.

기체 분리용 고분자 분리막의 분자동력학 연구

박치훈,김득주,남상용,Park, Chi Hoon,Kim, Deuk Ju,Nam, Sang Yong 한국막학회 2014 멤브레인 Vol.24 No.5

분자 동력학(Molecular dynamics; MD) 전산모사 기술은 대상이 되는 입자(일반적으로, 원자)의 위치와 속도를 계산하여, 원자 및 분자들의 다양한 구조 및 동적 특성을 분석하는 데에 있어서 매우 유용한 기술이다. 기체 분리막 연구에 있어서도 MD는 그동안 free volume 분석, conformation search 등과 같은 고분자 구조 분석 및 permeability, diffusivity와 같은 기체 투과 거동을 연구하는 데 널리 사용되어 왔다. 본 총설에서는 기체 분리막 분야에 MD를 적용하는 일반적인 방법론에 대하여 서술하고, 다양한 관련 연구들을 소개하고자 한다. Molecular dynamics (MD) computer simulation is a very useful tool to calculate the trajectory and velocity of particles (generally, atoms), and thus to analyze the various structures and kinetic properties of atoms and molecules. For gas separation membranes, MD has been widely used for structure analysis of polymers such as free volume analysis and conformation search, and for the study of gas transport behavior such as permeability and diffusivity. In this paper, general methodology how to apply MD on gas separation membranes will be described and various related researches will be introduced.

Atomistic Simulation of Sintering Mechanism for Copper Nano-Powders

Seong, Yujin,Hwang, Sungwon,Kim, See Jo,Kim, Sungho,Kim, Seong-Gon,Kim, Hak Jun,Park, Seong Jin The Korean Powder Metallurgy Institute 2015 한국분말재료학회지 (KPMI) Vol.22 No.4

The sintering mechanisms of nanoscale copper powders have been investigated. A molecular dynamics (MD) simulation with the embedded-atom method (EAM) was employed for these simulations. The dimensional changes for initial-stage sintering such as characteristic lengths, neck growth, and neck angle were calculated to understand the densification behavior of copper nano-powders. Factors affecting sintering such as the temperature, powder size, and crystalline misalignment between adjacent powders have also been studied. These results could provide information of setting the processing cycles and material designs applicable to nano-powders. In addition, it is expected that MD simulation will be a foundation for the multi-scale modeling in sintering process.

Molecular simulation study of water transport through aquaporin-inspired pore geometry

마지드,김대중 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.8

Water permeation dynamics through hourglass-shaped nanopore is addressed by using Molecular dynamics (MD) simulations. The objective of this research is to understand the variation of the length on water transport in hourglass-shaped pore. We found that the water flow decreases with length due to the hydrodynamic resistance at the entrances, that has large contribution on water flow. Moreover, it was shown that water flux decreases as the length increases, which is consistent with the experimental study. The fluctuations of the density profiles at the center of the pore reduce as the length increases, which is an indication of fast local permeability through highly continuous motion. The pore surface becomes highly frictionless with increasing the length due to the low water-wall interaction. On the other hand, the hydrodynamic resistance (viscos dissipation) at the center of the pore decreases as the length increases, whereas the entrance effect can be highlighted. The MSD curve indicates a Fickian diffusion with increasing the length, even though a Single-file diffusion is expected. It can be found that the changing the cone angle affects on flow rate enhancement through hourglass-shaped nanochannels.

Coil-to-globule transition of thermo-responsive γ-substituted poly (ɛ-caprolactone) in water: A molecular dynamics simulation study

Amin Koochaki,Mohammad Reza Moghbeli,Sousa Javan Nikkhah 한국물리학회 2018 Current Applied Physics Vol.18 No.11

The coil-to-globule behavior of poly{γ-2-[2-(2methoxyethoxy)ethoxy]ethoxy-3-caprolactone} (PMEEECL) as a γ- substituted poly (ɛ-caprolactone) was investigated via atomistic molecular dynamics (MD) simulation. For this purpose, radius of gyration, end-to-end distance and radial distribution function of the chain in the presence of water were calculated. Consequently, the lower critical solution temperature (LCST) of PMEEECL chain at which the coil-to-globule transition takes place, was determined in each calculated parameter curve. The simulation results indicated that the LCST of PMEEECL was occurred at close to 320 K, which is in a good agreement with previous experimental results. Additionally, the appearance of sudden change in both Flory-Huggins interaction parameter (χ) and interaction energy between the PMEEECL chain and water molecules at about 320 K confirmed the calculated LCST result. The radial distribution function (RDF) results showed that the affinity of the PMEEECL side chain to water molecules is lower than its backbone.

Water channel morphology of non-perfluorinated hydrocarbon proton exchange membrane under a low humidifying condition

Park, Chi Hoon,Kim, Tae-Ho,Nam, Sang Yong,Hong, Young Taik Elsevier 2019 International journal of hydrogen energy Vol.44 No.4

<P><B>Abstract</B></P> <P>Water channel formation of non-perfluorinated proton exchange membranes (PEMs) under a low humidifying condition is a very important issue, due to weaker phase separation between hydrophilic and hydrophobic moieties than in the case of perfluorinated PEMs such as Nafion. In this study, we performed Molecular dynamics (MD) simulations of hydrated sulfonated polyimide (SPI) models, one of the representative non-perfluorinated PEMs, under different temperature and humidifying conditions by removing water molecules continuously, reflecting experimental conditions of actual low humidifying fuel cell. The water channel morphology of sulfonated polyimide (SPI) models had no apparent temperature dependence. The hydrated SPI models show weak water channel formation even in a fully hydrated condition (λ = 16.4), consistent with our previous study, and they do not display significant temperature dependence on the water molecule distribution. As the λ value decreases from 16.4 to 2 (i.e., low humidifying conditions), the water molecules in the hydrated SPI models are evenly reduced. In particular, when the λ value of the hydrated SPI model decreases from 8.5 to 6, the size of the water clusters is significantly narrowed and the clusters become segregated, and this is also confirmed by an X-ray scattering analysis. As a result, the proton conducting performance of hydrated SPI models shows similar behavior with the change in water channel morphologies, which will be very important to design a novel non-perfluorinated hydrocarbon PEM with high performance for practical fuel cell systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Non-perfluorinated PEMs under low humidifying conditions were simulated by MD. </LI> <LI> The water channel morphology of SPI models had no apparent temperature dependence. </LI> <LI> The water clusters became narrowed and segregated at low λ value. </LI> <LI> Proton transport showed similar behavior with the change in water clusters. </LI> </UL> </P>

Recent Progress in Molecular Simulation of Nanoporous Graphene Membranes for Gas Separation

S. Mahmood Fatemi,Aminreza Baniasadi,Mahrokh Moradi 한국물리학회 2017 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.71 No.1

If an ideal membrane for gas separation is to be obtained, the following three characteristics should be considered: the membrane should be as thin as possible, be mechanically robust, and have welldefined pore sizes. These features will maximize its solvent flux, preserve it from fracture, and guarantee its selectivity. Graphene is made up of a hexagonal honeycomb lattice of carbon atoms with sp2 hybridization state forming a one-atom-thick sheet of graphite. Following conversion of the honeycomb lattices into nanopores with a specific geometry and size, a nanoporous graphene membrane that offers high efficiency as a separation membrane because of the ultrafast molecular permeation rate as a result of its one-atom thickness is obtained. Applications of nanoporous graphene membranes for gas separation have been receiving remarkably increasing attention because nanoporous graphene membranes show promising results in this area. This review focuses on the recent advances in nanoporous graphene membranes for applications in gas separation, with a major emphasis on theoretical works. The attractive properties of nanoporous graphene membranes introduce make them appropriate candidates for gas separation and gas molecular-sieving processes in nanoscale dimensions.

Structural investigation on the intrinsically disordered N-terminal region of HPV16 E7 protein

( Chewook Lee ),( Do Hyoung Kim ),( Si Hyung Lee ),( Jiulong Su ),( Kyou Hoon Han ) 생화학분자생물학회(구 한국생화학분자생물학회) 2016 BMB Reports Vol.49 No.8

Human papillomavirus (HPV) is the major cause of cervical cancer, a deadly threat to millions of females. The early oncogene product (E7) of the high-risk HPV16 is the primary agent associated with HPV-related cervical cancers. In order to understand how E7 contributes to the transforming activity, we investigated the structural features of the flexible N-terminal region (46 residues) of E7 by carrying out N-15 heteronuclear NMR experiments and replica exchange molecular dynamics simulations. Several NMR parameters as well as simulation ensemble structures indicate that this intrinsically disordered region of E7 contains two transient (10-20% populated) helical pre-structured motifs that overlap with important target binding moieties such as an E2F-mimic motif and a pRb-binding LXCXE segment. Presence of such target-binding motifs in HPV16 E7 provides a reasonable explanation for its promiscuous target-binding behavior associated with its transforming activity. [BMB Reports 2016; 49(8): 431-436]

Molecular dynamics simulation of transport characteristics of water molecules through high aspect ratio hourglass-shaped pore

Shahbabaei, M.,Kim, D. Elsevier 2016 Colloids and surfaces. A, Physicochemical and engi Vol.507 No.-

This research utilizes molecular dynamics (MD) simulations in order to study the effect of the length on water transport properties through the pore with an hourglass shape structure. While the narrowest section of the pore is kept constant, the length of the pore is increased in the range of 100-200A. The narrowest section allows water molecules to cross just in single-file configuration. It observed that flow decreases as the length increases unlike the water flux which increases with length, which attributes to the frictionless surface of the pore. In comparable with flux, the efficiency increases as the length increases. The increase of the diffusion coefficient and permeability together suggest that the entrance effect can be negligible as the length increases. It revealed that the friction force decreases with increasing the length. On the other hand, the displacement of water molecules from wall increases with length. These results together suggest that as the length increases the wall surface becomes frictionless.

Penetration of C60 into lung surfactant membranes: Molecular dynamics simulation studies

Hyun Jiyeon,Chang Rakwoo 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.3

We performed molecular dynamics simulations of the systems consisting of C60 molecules and dipalmitoylphosphatidylcholine (DPPC) monolayer membranes to study the penetration of C60 into lung surfactant (LS) membranes. The potential of mean force of the C60 penetration through the LS membrane was calculated as a function of the distance of a C60 molecule from the DPPC monolayer membrane. The free energy minimum of around 43 kcal/mol is located in the DPPC tail region, indicating that the C60 molecules can accumulate in the LS membrane region. The energy decomposition shows the main driving force of the C60 accumulation in the lipid tail region is the van der Waals interaction with the hydrocarbon tails of DPPC lipids. Finally, we observed that the water evaporation rate can be significantly enhanced by the accumulation of C60 molecules in the membrane tail region.