http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Can Polymer Chains Cross Each Other and Still Be Entangled?
Chang, Rakwoo,Yethiraj, Arun American Chemical Society 2019 Macromolecules Vol.52 No.5
<P>The effect of chain crossing on polymer entanglement behavior is studied using molecular dynamics simulations of linear hard-sphere chains. The degree of chain crossing is controlled by changing the amplitude of bond vibrations while keeping the average bond length fixed. When the vibration amplitude is small, chain crossing is strictly prohibited, but for larger amplitudes the chains can cross. When chain crossing is strictly prohibited, the apparent scaling of the self-diffusion coefficient, <I>D</I>, and rotational relaxation time, τ<SUB>R</SUB>, with degree of polymerization, <I>N</I>, is consistent with entangled behavior, and when chains cross freely Rouse dynamics is recovered. There is an intermediate regime, however, when chains are allowed to cross, but crossing events are rare. Under these conditions entanglement behavior is recovered. We therefore conclude that polymer chains can cross and still be entangled for finite length chains. There is no discernible change in the intermolecular static structure factor between the unentangled and entangled systems.</P> [FIG OMISSION]</BR>
Dynamics of C60 Molecules in Biological Membranes: Computer Simulation Studies
Rakwoo Chang,Jumin Lee 대한화학회 2010 Bulletin of the Korean Chemical Society Vol.31 No.11
We have performed molecular dynamics simulations of atomistic models of C60 molecules and DMPC bilayer membranes to study the static and dynamic effects of carbon nanoparticles on biological membranes. All four C60-membrane systems were investigated representing dilute and concentrated solutions of C60 residing either inside or outside the membrane. The concentrated C60 molecules in water phase start forming an aggregated cluster. Due to its heavy mass, the cluster tends to adhere on the surface of the bilayer membrane, hindering both translational and rotational diffusion of individual C60. On the other hand, once C60 molecules accumulate inside the membrane, they are well dispersed in the central region of the bilayer membrane. Because of the homogeneous dispersion of C60 inside the membrane, each leaflet is pushed away from the center, making the bilayer membrane thicker. This thickening of the membrane provides more room for both translational and rotational motions of C60 inside the membrane compared to that in the water region. As a result, the dynamics of C60 inside the membrane becomes faster with increasing its concentration.
Na Jihye,Chang Rakwoo 대한화학회 2021 Bulletin of the Korean Chemical Society Vol.42 No.7
We have performed coarse-grained molecular dynamics simulations of organic photovoltaic (OPV) 5wcells consisting of poly(3-hexyl-thiophene) (P3HT), phenyl-C61-butyric acid methyl ester (PC61BM), and phenyl-C71-butyricacid methyl ester (PC71BM) to investigate the effects of the solvent evaporation rate and the number of components in the morphological stability of OPV. Two different solvent evaporation processes were employed in this study. In the instantaneous solvent removal process, unstable pores are formed because of the slow translational relaxation of the electron receptors. In case of the gradual solvent removal process, the stable film formation is observed without any pore. In addition, the ternary OPV system shows better stability than binary systems by slowing down the phase separation.
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.