Positron Lifetime Studies of the Local Free Volume in Elastomer Modified Thermoplastics

Dlubek, G.; Fretwell, H. M.; Alam, and Ashraf

doi:10.1002/(sici)1521-396x(199806)167:2<r13::aid-pssa999913>3.0.co;2-x

Cited by 7 publications

(6 citation statements)

References 4 publications

(5 reference statements)

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“…To understand the many rules governing material properties of polymer systems, it would be highly desirable to have a multiscale model which can include all relevant interactions . Experimental techniques such as NMR spectroscopy, − atomic force microscopy, position annihilation spectroscopy, and dielectric spectroscopy have been developed to obtain a detailed description of the static and dynamic properties of polymeric systems from local chain arrangements up to the behavior of the polymeric materials in macroscale applications. Techniques covering the whole range of length scales together do not exist in computer simulation to date.…”

Section: Introductionmentioning

confidence: 99%

Crossover from Unentangled to Entangled Dynamics in a Systematically Coarse-Grained Polystyrene Melt

2005

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We develop a mesoscale polystyrene model based on atomistic simulations of oligomers using the iterative Boltzmann inversion method. The potential is optimized against the atomistic simulation until the radial distribution function generated from the mesoscale model is consistent with the atomistic simulation. The mesoscale model allows to elucidate the polymer dynamics of long chains. The dynamics of polystyrene melts are investigated at various chain lengths between 15 and 240 monomers. Mean-squared displacements are analyzed to capture the dynamics changing from the Rouse to the reptation behavior. The reorientation behavior of segmental vectors is investigated to identify the heterogeneity along the chain. Diffusion constants of various systems are calculated to verify the crossover from the unentangled to entangled dynamics. Rouse mode analysis shows that the Rouse model is applicable from chain length between 50 and 100 monomers. The entanglement length of this polystyrene model is around 85 monomers at 450 K, in fair agreement with experiments.

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Section: Introductionmentioning

confidence: 99%

Crossover from Unentangled to Entangled Dynamics in a Systematically Coarse-Grained Polystyrene Melt

2005

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“…Several experiments have been performed aimed at the local properties of polyisoprene like reorientation times and the packing. [8][9][10][11][12][13] Additionally, simulations of pure cis-polyisoprene are already known. 1,14 To our knowledge there are, however, not yet simulations of the trans conformer.…”

Section: Introductionmentioning

confidence: 99%

“…For the properties under investigation short chains are sufficient, as the connectivity and noncrossability contribute to phenomena on the generic large-scale level , which is not of interest here. Several experiments have been performed aimed at the local properties of polyisoprene like reorientation times and the packing. − Additionally, simulations of pure cis -polyisoprene are already known. , To our knowledge there are, however, not yet simulations of the trans conformer. Industrially, this conformer is not as important as the cis conformer.…”

Section: Introductionmentioning

confidence: 99%

Local Structure and Dynamics of trans-Polyisoprene Oligomers

et al. 2001

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Mono-and poly-disperse melts of oligomers (average length 10 monomers) of trans-1,4-polyisoprene are simulated in full atomistic detail. The force-field is developed by means of a mixture of ab initio quantum-chemistry and an automatic generation of empirical parameters. Comparisons to NMR and scattering experiments validate the model. The local reorientation dynamics shows that for C−H vectors there is a two-stage process consisting of an initial decay and a late-stage decorrelation originating from overall reorientation. The atomistic model can be successfully mapped onto a simple model including only beads for the monomers with bond springs and bond angle potentials. End-bridging Monte Carlo as an equilibration stage and molecular dynamics as the subsequent simulation method together prove to be a useful method for polymer simulations.The two polydisperse systems (systems 2 and 3) were additionally equilibrated using the endbridging Monte Carlo (EBMC) procedure 16, 17 before the molecular dynamics simulations were performed at a constant pressure of 101.3 kPa to determine the density in a poly-disperse melt. We used two systems with slightly different chain length distributions (see below) in order to increase the statistics and to look for influences of the actual realization of the ensemble.The EBMC was performed in a united-atom model as the positions of the hydrogens are not important at this stage. The non-bonded interaction potential parameters for this procedure are

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“…It finds use in thermoplastic materials used for making telephone hand sets, refrigerator liners safety helmets, radio components, roofing, flooring paints, adhesives. Recently, structural and dynamical behavior of TPI on the local scale has been reported by several workers [5][6][7][8].…”

Section: Introductionmentioning

confidence: 97%