• Title, Summary, Keyword: molecular properties

Search Result 3,625, Processing Time 0.055 seconds

The Calculation of Physical Properties of Amino Acids Using Molecular Modeling Techniques (II)

  • Lee, Myung-Jae;Kim, Ui-Rak
    • Bulletin of the Korean Chemical Society
    • /
    • v.25 no.7
    • /
    • pp.1046-1050
    • /
    • 2004
  • Six physical properties (enthalpy, density, decomposition temperature, solubility in water, pKa values, and hydronium potential) were examined by molecular modeling techniques. The molecular connectivity index, Wiener distance index, and Ad hoc descriptor are employed as structural parameters to encode information about branching, size, cyclization, unsaturation, heteroatom content, and polarizability. This paper examines the correlation of the molecular modeling techniques parameters and the physicochemical properties of amino acids. As a results, calculated values were in agreement with experimental data in the above six physical properties of amino acids and the molecular connectivity index was superior to the other indices in fitting the calculated data.

High Molecular Weight Conjugated Polymer Thin Films with Enhanced Molecular Ordering, Obtained via a Dipping Method

  • Park, Yeong Don
    • Bulletin of the Korean Chemical Society
    • /
    • v.34 no.11
    • /
    • pp.3340-3344
    • /
    • 2013
  • The fabrication of polymer field-effect transistors with good electrical properties requires the minimization of molecular defects caused by low molecular weight (MW) fractions of a conjugated polymer. Here we report that the electrical properties of a narrow bandgap conjugated polymer could be dramatically improved as a result of dipping a thin film into a poor solvent. The dipping time in hexanes was controlled to efficiently eliminate the low molecular weight fractions and concomitantly improve the molecular ordering of the conjugated polymer. The correlation between the structural order and the electrical properties was used to optimize the dipping time and investigate the effects of the low MW fraction on the electrical properties of the resulting thin film.

From Gas Phase Clusters to Nanomaterials: An Overview of Theoretical Insights

  • Kim, Kwang-S.
    • Bulletin of the Korean Chemical Society
    • /
    • v.24 no.6
    • /
    • pp.757-762
    • /
    • 2003
  • Since theoretical investigations of gas phase clusters enable the evaluation of intrinsic molecular properties and intermolecular interactions, one can predict the macroscopic properties of bulk matter, from a microscopic determination of the properties of individual atoms, molecules, or clusters. Based on the insights obtained from theoretical investigations of the properties of a large number of cluster systems (ranging from simple water clusters to large π-systems), we have investigated the properties of various novel molecular systems including endo/exohedral fullerenes, nanotori, nonlinear optical materials, ionophores/receptors, polypeptides, enzymes, organic nanotubes, nanowires, and electronic and nano-mechanical molecular devices. The present minireview highlights some of the interesting results obtained in the course of our extensive theoretical investigations of clusters and nanomaterials.

The Calculation of Physical Properties of Amino Acids using Molecular Modeling Techniques

  • Ui-Rak Kim;Kyung-Sub Min;Bong-Jin Jeong
    • Bulletin of the Korean Chemical Society
    • /
    • v.15 no.2
    • /
    • pp.106-112
    • /
    • 1994
  • Six physical properties (molecular weight, heat capacity, side chain weight, side chain volume, standard entropy and partial molar volume) of amino acids, peptides and their derivatives were examined by molecular modeling techniques. The molecular connectivity index, Wiener distance index and ad hoc descriptor are employed as structural parameters to encode information about branching, size, cyclization, unsaturation, heteroatom content and polarizability. This paper examines the correlation of the molecular modeling techique's parameters and the physicochemical properties of amino acids and their derivatives. As a result, calculated values were in agreement with experimental data in the above six physical properties of amino acids, peptides and their derivatives and the molecular connectivity index was superior to the other indices in fitting the calculated data.

  • PDF

MS-HEMs: An On-line Management System for High-Energy Molecules at ADD and BMDRC in Korea

  • Lee, Sung-Kwang;Cho, Soo-Gyeong;Park, Jae-Sung;Kim, Kwang-Yeon;No, Kyoung-Tae
    • Bulletin of the Korean Chemical Society
    • /
    • v.33 no.3
    • /
    • pp.855-861
    • /
    • 2012
  • A pioneering version of an on-line management system for high-energy molecules (MS-HEMs) was developed by the ADD and BMDRC in Korea. The current system can manage the physicochemical and explosive properties of virtual and existing HEMs. The on-line MS-HEMs consist of three main routines: management, calculation, and search. The management routine contains a user-friendly interface to store and manage molecular structures and other properties of the new HEMs. The calculation routine automatically calculates a number of compositional and topological molecular descriptors when a new HEM is stored in the MS-HEMs. Physical properties, such as the heat of formation and density, can also be calculated using group additivity methods. In addition, the calculation routine for the impact sensitivity can be used to obtain the safety nature of new HEMs. The impact sensitivity was estimated in a knowledge-based manner using in-house neural network code. The search routine enables general users to find an exact HEM and its properties by sketching a 2D chemical structure, or to retrieve HEMs and their properties by giving a range of properties. These on-line MS-HEMs are expected be powerful tool for deriving novel promising HEMs.

The Effect of Changing Molecular Weight of Rosin Modified Phenol Resin on Physical Properties of Litho Printing Inks (Rosin변성 phenol수지의 분자량 변화에 따른 평판인쇄 잉크의 물성변화에 관한 연구)

  • SungBinKim
    • Journal of the Korean Printing Society
    • /
    • v.12 no.1
    • /
    • pp.145-157
    • /
    • 1994
  • Litho printing ink vehicles based on rosin modified phenolic are faster drying, have better durability, are harder and glosser and have greater resistance to water than ones based on ester gums. Ink-Water balance and rheological properties are important in litho printing process. These physical properties is concerned with molecular weight of Resin to use vehicle. So this paper was studied about the effects of changing molecular weight of Rosin modified phenolic on surface tension, viscosity, pseudoplasticity and printability of Litho Inks. The results were as follows. 1) The surface tension of model inks depended on the molecular \veight of the resin : Dispersion componnent of ink increase but non dispersion component decrease as molecular weight of Resin increase. 2) Water pick-up of litho ink is more fast balance, using low molecular weight of Resin. 3) Viscosity, Yield value and Newtonian value of model inks increase as molecular weight of Resin increase. 4) The litho ink prepared with the modified phenolic of which molecular weight is about 20000 showed the highest printing density and gloss.

  • PDF

Molecular Dynamics Simulation on thermodynamic and Structural Properties of Liquid Hydrocarbons : Normal Alkanes

  • Im, Won-Pil;Won, Young-Do
    • Bulletin of the Korean Chemical Society
    • /
    • v.15 no.10
    • /
    • pp.852-856
    • /
    • 1994
  • A series of aliphatic hydrocarbons, methane to hexane in the liquid state, are modeled with the molecular mechanical potential parameters treating all hydrogen degrees of freedom explicitly. Thermodynamic properties (heat capacities and heats of vaporization) are calculated from relatively short (20ps) molecular dynamics trajectories. The liquid state structures are also examined through various radial distribution functions. Molecular dynamics simulations reproduce experimentally measured properties within a few percent errors, thus indicate that the present set of all-hydrogen parameters is suitable for simulating macromolecular systems in bulk.

  • PDF

Molecular Modeling of Bisphenol-A Polycarbonate and Tetramethyl Bisphenol-A Polycarbonate

  • Kim, Sangil;Juwhan Liu
    • Macromolecular research
    • /
    • v.9 no.3
    • /
    • pp.129-142
    • /
    • 2001
  • To efficiently demonstrate the molecular motion, physical properties, and mechanical properties of polycarbonates, we studied the differences between bisphenol-A polycarbonate(BPA-PC) and tetramethyl bisphenol-A-polycarbonate(TMBPA-PC) using molecular modeling techniques. To investigate the conformations of BPA-PC and TMBPA-PC and the effect of the conformation on mechanical properties, we performed conformational energy calculation, molecular dynamics calculation, and stress-strain curves based on molecular mechanics method. From the result obtained from conformational energy calculations of each segment, the molecular motions of the carbonate and the phenylene group in BPA-PC were seen to be more vigorous and have lower restriction to mobility than those in TMBPA-PC, respectively. In addition, from the results of radial distribution function, velocity autocorrelation function, and power spectrum, BPA-PC appeared to have higher diffusion constant than TMBPA-PC and is easier to have various conformations because of the less severe restrictions in molecular motion. The result of stress-strain calculation for TMBPA-PC seemed to be in accordance with the experimental value of strain-to-failure ∼4%. From these results of conformational energy calculations of segments, molecular dynamics, and mechanical properties, it can be concluded that TMBPA-PC has higher modulus and brittleness than BPA-PC because the former has no efficient relaxation mode against the external deformations.

  • PDF

Statistical Analysis for Turbulence Properties of the Orion Molecular Cloud

  • Yun, Hyeong-Sik;Lee, Jeong-Eun;Choi, Yunhee;Lee, Seokho;Choi, Minho;Kang, Hyunwoo;Tatematsu, Ken'ichi;Offner, Stella S.R.;Gaches, Brandt A.L.;Heyer, Mark H.;Evans, Neal J. II;Yang, Yao-Lun
    • The Bulletin of The Korean Astronomical Society
    • /
    • v.41 no.2
    • /
    • pp.55.5-56
    • /
    • 2016
  • Turbulence plays an important role in molecular clouds. However, the properties of turbulence are poorly understood. In order to study the influence of turbulence in molecular clouds, we need to sample the turbulent properties in the full range of scales down to sonic scale. We mapped the $20^{\prime}{\times}60^{\prime}$ area covering the Orion Molecular Cloud (OMC) 1-4 region in HCN 1-0 and HCO+ 1-0 with Taeduk Radio Astronomy Observatory (TRAO) 14-m telescope as part of the TRAO key science program, "Mapping turbulent properties of star-forming molecular clouds down to the sonic scale (PI: Jeong-Eun Lee)". In addition, we combine our TRAO data with other molecular line maps ($^{13}CO$ 1-0, $C^{18}O$ 1-0, CS 1-0, $N_2H^+$ 1-0) obtained with the Nobeyama Radio Observatory (NRO) 45-m telescope. To analyze these data, we apply statistical methods, the principal component analysis (PCA) and spectral correlation function (SCF), which are known to be useful to study underlying turbulent properties and to quantitatively characterize cloud structure. We will present the preliminary results of observations and analyses.

  • PDF

Environmental Effects on the Molecular Gas Properties of Cluster Spirals

  • Jeong, Eun-Jeong;Jeong, Ae-Ri;Lee, Myeong-Hyeon
    • The Bulletin of The Korean Astronomical Society
    • /
    • v.36 no.1
    • /
    • pp.62.2-62.2
    • /
    • 2011
  • It is well known that the cluster environment can change the atomic gas properties of galaxies through tidal interactions and/or by the hot cluster medium. Meanwhile, the molecular gas is expected to be less vulnerable to its surroundings due to its higher density, and no obvious influence of the environment on the molecular gas properties had been found among cluster spirals until recently. However, in a recent study by Fumagalli et al. (2009) of a sub-sample of Virgo spirals, it has been suggested that HI deficient galaxies can be also CO deficient. In order to further investigate if the HI deficiency indeed can result in the deficiency in molecular gas content, we compare the global CO and HI gas properties of Virgo spirals with those of galaxies in the Ursa Major cluster and the Pisces cluster, much lower density environments than Virgo. We discuss possible consequences of molecular gas deficiency in star formation activity of spiral galaxies in high density environment.

  • PDF