Theoretical chemistry articles within Polymer Journal

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  • Focus Review |

    Reverse osmosis (RO) membranes are widely used as energy-saving and environmentally friendly materials for water purification. This Focus Review reports on the nanoscale structure and permeation mechanism of crosslinked fully aromatic polyamide RO membranes. First, the research on the morphology of protuberance structures of the polyamide separation functional layer is described. Next, hydrated structure of the functional layer is focused, which was analyzed using neutron scattering and molecular dynamics simulations. Innovative RO membranes are being developed that can obtain higher quality water with less energy by precisely controlling nanostructures.

    • Harutoki Shimura

  • Original Article |

    We investigated the functions that reproduce the configurational heat capacity (Cconfig) that occurs above the glass transition temperature for polystyrene (PS), polyisobutylene (PIB), and their oligomers. The results show that Cconfig could be well reproduced using the power and logarithmic functions based on the Landau theory. The power and logarithmic functions had four and three fitting parameters, respectively. The error ranges were approximately ±2% for PS and ±5% for PIB. At this stage, the two functions are not functions with the clear physical meanings but the practical functions that were evaluated using regression analysis and simply reproduce the configurational heat capacity.

    • Eri Nishiyama
    • , Marika Yokota
    •  & Itaru Tsukushi

  • Original Article |

    This study comprehensively reveal the critical parameters of poly(ethylene oxide) (PEO) in the MD simulation that causes the numerical effect on polymer simulation and the variation of thermodynamics property. The threshold value of total molecular weight of 11,240 g/mol must be satisfied, which leads the polymer that exhibits its steady state bulk properties. For the oligomer system (Mw < 2248 g/mol per chain (50 monomers)), the total chain number must be more than 10 at least. The cooling rate must be lower than 5 × 1013 K/min for the structural equilibrium.

    • Yao-Chun Wang
    • , Jun-Fu Zhang
    •  & Wen-Jay Lee

  • Original Article |

    With the aim of gaining more insight into the heat capacity of amorphous polymers and considering that there are more than a dozen types of data on the absolute value of the heat capacity of polymer compounds, we evaluated the heat capacity of 16 main-chain-type amorphous polymers composed of a carbon backbone using a combination of the Tarasov equation, Einstein equation, and the (Cp − CV) correction term by taking into account the degree of freedom of monomer units. We found that the heat capacity of the analyzed amorphous polymers could be reproduced using only three fitting parameters from a combination of the Tarasov and Einstein equations below glass transition temperature.

    • Marika Yokota
    • , Kaito Sugane
    •  & Mitsuhiro Shibata

  • Note |

    Suppression of protein adsorption on polymeric interfaces is one of the significant challenges in developing novel biomedical polymers. In this study, the computational design of an antifouling polymer repeat unit is conducted based on a simple approach, whereby the intermolecular affinities between a probe molecule and a polymer repeat unit are evaluated to generate free energy profiles using molecular dynamics simulations. The simplified method affords convenient and theoretical screening of highly antifouling polymer repeat units.

    • Ryo Nagumo
    • , Shohei Terao
    •  & Hiromitsu Takaba

  • Original Article |

    The structures and electronic states in polymorphs (Forms I–IV) of PVDF were calculated by the density functional theory at PBE0/cc-pVTZ level. The calculated lattice constants agreed well with experimental values. Derived electronic and vibrational frequencies corresponded closely with the experimental vXPS and IR/Raman spectra, respectively. The amounts of spontaneous polarization in the polar crystal forms (I, III, and IV) were calculated. Those for Forms III and IV were determined for the first time.

    • Akira Itoh
    • , Yoshiyuki Takahashi
    •  & Hirofumi Yajima

  • Original Article |

    We performed molecular dynamics simulation of liquid-crystalline epoxy resin. For the simulation, one molecule is modeled as a diamine ends of which are connected to derivatives of diepoxy mesogens. Molecular ends were drawn by external force in order to generate well-aligned initial structure. After removing the external force, equilibrated results expressed an even–odd effect for number of methylene units of mesogenic structures. Finally we propose a recipe to use the present simulation for a screening to obtain epoxy molecules of higher thermal conductivity.

    • Tomonori Koda
    • , Toshiyuki Toyoshima
    •  & Ken Miyata

  • Original Article |

    Structure and molecular mobility of nascent iPP powder were investigated by differential scanning calorimetry, transmission electron microscopy and solid-state nuclear magnetic resonance (NMR). Combination of NMR with other analytical method provides the deep insight and concluded that the crystalline size of nascent powder is extremely small and the crystalline phase is easily affected by the surrounded noncrystalline phase.

    • Takeshi Yamanobe
    • , Katsunori Ueki
    •  & Hiroki Uehara

  • Original Article |

    Bacteriorhodopsin (bR) has a retinal with all-trans and 13-cis, 15-syn configurations whose isomeric ratio is close to 1 in the dark and the population of 13-cis, 15-syn configuration can be increased under the pressurized condition. Increase of pressure by fast magic angle spinning (MAS) induced dynamics change at around Ala81 and Ala84 in bR together with retinal isomerization from all-trans to 13-cis configurations. We demonstrated that fast MAS NMR provides a pressure sauce for investigating the structure and dynamics change of biomacromolecules.

    • Izuru Kawamura
    • , Satoru Yamaguchi
    •  & Akira Naito

  • Note |

    Microscopic behaviors of explicit water molecules on biocompatible zwitterionic self-assembled monolayer (SAM) surfaces were investigated by molecular dynamics simulations. The orientational distribution of water molecules near the surfaces was evaluated to analyze its structural properties. Consequently, water molecules on the zwitterionic SAMs are randomly oriented. In contrast, those near the surface of poly(vinyl alcohol) are highly oriented, resulting from the structured hydrogen bonding network. Microscopic properties of water molecules on the interfaces would have a key role in the suppression of protein adsorption for zwitterionic biomaterials.

    • Ryo Nagumo
    • , Tatsunori Ito
    •  & Akira Miyamoto

  • Invited Review |

    Antifreeze proteins (AFPs) function as inhibitors of ice growth. Computer simulation studies have contributed to the understanding of the molecular-scale mechanism of ice growth inhibition by AFPs. For example, molecular dynamics simulations of a growing ice–water interface to which a winter flounder AFP for a {20\(\overline{2}\)1} pyramidal plane is bound have indicated that the growth rate of ice surrounding the AFP decreases drastically, owing to depression of the ice melting point through the Gibbs–Thomson effect.

    • Hiroki Nada
    •  & Yoshinori Furukawa

  • Original Article |

    Temperature-dependent curves of T1H for the SBR with and without end-chain modification in the SBR/Si composites showed the increment of the T1H values as the MAS rate increases and the considerable change at the fast MAS rate of 25 kHz. The increase of T1H values is represented by the factor f that decides the observed T1H minimum value. The plot of centrifugal pressure caused by MAS as a function of 1/f exhibited the similar trend to that of the stress–strain curve. The differences in the T1H between the end-chain-modified and normal SBR under fast MAS was attributed to the Payne effect.

    • Atsushi Asano
    • , Shunsuke Hori
    •  & Takuzo Kurotsu

  • Original Article |

    The hydrophobic association of fluorocarbon-modified polyacrylamide aqueous solutions has been investigated on a mesoscopic level by considering the variation of root mean square (RMS) end-to-end distances using dissipative particle dynamics (DPD) simulation. Its hydrophobic association property is affected by the type of the hydrophobic group, salt, temperature and shear. The unit of stronger hydrophobic property within the chain makes the macromolecule have the greatest association in the solution.

    • Tao Ni
    • , Guang-Su Huang
    •  & Ming-Zhu Yang

  • Original Article |

    X-ray reflectivity measurements are performed on polystyrene thin films supported on Si substrates at various heating and cooling rates. With decreasing thickness, the width of the glass transition (w) shows an appreciable variation that depends on the rate of temperature variation: broadening at a rate of 0.5 °C min−1, no broadening at a rate of 0.05 °C min−1 and narrowing at a rate of 0.01 °C min−1.

    • Chunming Yang
    •  & Isao Takahashi

  • Original Article |

    The second and third virial coefficients (A2 and A3, respectively) for benzyl-end polystyrene in toluene at 15 °C are determined by light scattering. The figure shows that A2 data for benzyl-end (unfilled circles) and butyl-end (filled circles, literature data) polystyrenes can be fitted by the theoretical curves (solid and dashed curves) when the chain-end effect is incorporated into the theory without that effect (dotted curve).

    • Hiroshi Okada
    • , Shuhei Matsumoto
    •  & Yo Nakamura

  • Original Article |

    The weak gel was prepared by polycondensation of polyacrylamide and resol. The reaction mechanism was clarified by molecular simulation and experiment characterization. The reaction thermodynamics was analyzed to judge the reaction possibility by DMol3. Reaction dynamics were applied to determine the predominant reaction by transition state research, and the results of X-ray photoelectron spectrum confirmed the simulation results.

    • Tao Ni
    • , Guang-Su Huang
    •  & Meng-Meng Chen

  • Invited Article |

    The molecular dynamics and orientation of vulcanized natural rubber stretched at low extension ratio were studied by solid-state 13C NMR and density functional theory (DFT) calculations. Isoprene units of the oriented rubber chains in stretched NR rotate rapidly around an axis that almost aligned with C=C bond direction of polyisoprene.

    • Hideaki Kimura
    • , Hidehiko Dohi
    •  & Tetsuo Asakura

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