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  • American Institute of Physics (AIP)  (5)
  • 1995-1999  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    The nature of flexible linear polyelectrolytes in salt free solution: A molecular dynamics study (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 1669-1690 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present results of molecular dynamics simulations of linear polyelectrolytes in solution. The fundamental model for polyelectrolytes in solution is studied. Specifically, simulations are performed for multichain systems of a flexible chain model of charged polymers. The full Coulomb interactions of the monomers and counterions are treated explicitly. Experimental measurements of the osmotic pressure and the structure factor are reproduced. The simulations reveal a new picture of the chain structure based on calculations of the structure factor, persistence length, end-to-end distance, etc. We present a detailed discussion of the chain structure and a comparison with present theories. In contrast to the predicted dilute limit of rodlike chains, we find that the chains have significant bending at very low densities. Furthermore, the chains contract significantly before they overlap. We also show that counterion condensation dramatically alters the chain structure. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470698
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  • 2
    Electronic Resource
    Electronic Resource
    Efficient continuum model for simulating polymer blends and copolymers (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 10583-10594 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An efficient continuum model for simulating polymer blends and copolymers is presented. In this model, the interactions are short-range and purely repulsive, thus allowing for excellent computational performances. The driving force for phase separation is a difference in the repulsive interaction strength between like and unlike mers. The model consists essentially of a molecular-dynamics algorithm, supplemented by an appropriate Monte Carlo exchange process. To demonstrate the effectiveness of the model we study two systems, a symmetric binary blend of polymers and a symmetric diblock copolymer system. For the binary blend, we determine the phase diagram and find, as predicted by theory, that the critical interaction parameter scales with the inverse of the chain length of the polymers. For the diblock copolymer system, we study both the one-phase region and the microphase separated lamellar region. For the latter, we show that constant-pressure algorithms are more appropriate since, contrary to recent lattice simulations, the lamellar spacing can self-adjust in such an ensemble. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472978
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  • 3
    Electronic Resource
    Electronic Resource
    From many monomers to many polymers: Soft ellipsoid model for polymer melts and mixtures (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 4340-4348 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present an extremely efficient and rather general model in which whole polymer chains are represented as soft particles. The particles are characterized by their overall sizes and shapes, as given by the conformations of the underlying chains. The probability of occurrence of a particle with a given size determines its internal free energy. The density of monomers within each particle is calculated from all conformations that have the same size. The interaction between two particles is taken to be proportional to the spatial overlap of their monomer density distributions. When a large number of such particles are brought into contact, as is the case for a polymer melt, the interactions between the particles force them to shrink and modify the equilibrium size distribution. We show by simulations that this model leads to a Gaussian statistics of the chains in melt. Since the internal degrees of freedom of a chain are integrated out, a large number (of order 104) of long (e.g., N=100) chains can be simulated within reasonable computer time on a single work-station processor. A straightforward extension of this model is used to study symmetric polymer blends. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475835
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  • 4
    Electronic Resource
    Electronic Resource
    A new mechanism for penetrant diffusion in amorphous polymers: Molecular dynamics simulations of phenol diffusion in bisphenol-A-polycarbonate (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 6061-6068 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Atomistic molecular dynamics simulations are performed to analyze the diffusion of phenol molecules in a bisphenol-A-polycarbonate melt in the zero concentration limit for the temperature range from 500 K to 640 K. The transition from a hopping diffusion to a continuous diffusion is observed. Visualization of the diffusion process reveals a strong coupling between the polymer dynamics, i.e., size and shape fluctuations of the pore space and the hopping of the penetrant. Proper equilibration of the melt has been ensured by application of a novel multiscale simulation approach. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479904
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  • 5
    Electronic Resource
    Electronic Resource
    Time–temperature and time–density superposition in the simulation of rheological properties of polymers (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 3288-3293 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Applying a periodical elongational strain in a computer simulation of polymer melts and networks, we are able for the first time to employ a time–temperature and time–density superposition in a numerical experiment for the study of the dynamic moduli. The simulation results can be analyzed and understood within the semiempirical free volume concept. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479608
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