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In molecular dynamics (MD) simulation, the crystallization behavior of a polymer nanoglobule was studied as a function of temperature. The crystallinity in the nanoglobule was determined by using the site order parameter method [Macromolecules, 2008, 41: 6733]. The isothermal crystallization kinetics was determined at different temperatures and the rate of crystallization, K c , and the Avrami...
Simulations in conjunction with Raman scattering were performed to determine the conformational distortion of the α′ form of poly(lactic acid) (PLA). Based on packing constraints of an overall helical structure, the chain conformation can only be approximated by slight deviations from a tg’t chain conformation. Models were generated with different types of random departures from the expected dihedral...
Poly(lactic acid) samples rich in α′ or α crystals have been characterized using spectroscopic and thermal methods. Cryogenic infrared and Raman spectroscopy were used to probe the differences in chain conformation and packing. Compared to the α crystal, the α′ crystal has weakened specific carbonyl and methyl interactions. Experimental spectroscopic analysis in conjunction with simulation studies...
The structure and morphology of polyethylene (PE) produced during solution polymerization using bis(imino)pyridyl metal catalysts supported by flat SiO 2 /Si(100) wafers were investigated by atomic force microscopy (AFM) and electron diffraction. Depending on the polymerization temperature, ranging from RT to 85°C, different morphologies of the nascent PE have been observed. “Sea weed” like...
The conformational transition behavior of polymer in the amorphous state has been investigated through molecular dynamics simulations across the glass transition temperature (T g ). We find that the conformational transition, a localized and short time dynamics feature, crosses over different barrier heights when the system transforms from the molten state into the glass state and the barrier...
In the present study, the degree of chain interpenetration was considered as a structural attribute of the entanglements in polymer chain system. Inter-chain radial distribution function (RDF) was used to perform this measurement. We applied this method to a model system, in which an ordering process in the early stage of polymer crystal nucleation at the atomistic level was simulated by means of...
The molecular mechanics (MM) method with COMPASS force field was used to study the H-bonds in polyurethane with carboxyl (PUc), which has multiple donors and acceptors. 2-Methyl-3-{[(methylamino)carbonyl]oxy}propanoic acid was used as the model molecule. It was found that the model PUc possesses four conformers with lowest energy. Considering six possible H-bond types such as OH⋯OC(OH) (Type I), OH⋯OH(CO)...
The properties of ethylenediamine (EDA) cored and amine surface poly(amidoamine) (PAMAM) dendrimers of generation 1 through 7 in the explicit solvent were studied by the atomistic force field based molecular dynamics. Since amines are assumed to be protonated the simulation condition is designed to represent the dilute alkali solution. All the generations are spherical in shape, while the higher generations...
To improve the accuracy of polymer interfacial tension measurement using deformed drop retraction method (DDRM), we examined some factors, such as the shape parameter, the retraction scale D 0 , and the distortion criterion γ by means of dissipative particle dynamics (DPD) simulation with 6 different models and analysis with three observation data, and proposing a new shape parameter P. Results...
The process experimentally measuring the interfacial tension of polymers was simulated by means of dissipative particle dynamics (DPD) simulation method in the present study. It is a retraction of ellipsoid drop of a polymer within the other polymer bulk. Effect of the initial geometry of the ellipsoid on the finally obtained interfacial tension was focused, since it was found the ellipsoid might...
The conformational distribution change of amorphous poly(lactic acid) (PLA) induced by deformation has been studied using Raman spectroscopy. Spectroscopic features associated with the rotational isomeric states (ttt, ttg', tg't, tg'g') have been established experimentally and supported by normal coordinate analysis. Deformation induced a significant increase in the most favorable tg't conformation...
Molecular dynamics simulations of merging process of two isolated cyclic chains and that of linear chains have been performed, in order to find the difference between the two kinds of chain in bulk and in vacuum, where surface of the system restrains thousands of configurations showing up. Analysis indicates that in such confinement the chain ends at most moments float on the surface layer, and their...
The molecular mechanics (MM) method with COMPASS force field was used to study the H-bonds in the polyether based polyurethane model molecules. Availability of the calculation was firstly verified in comparison of some H-bonded model molecules, which were studied by using ab initio calculation, and those calculated by MM. Based on a urethane model molecule 1,3-dimethylcarbamate, which can be donor...
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