A Molecular Modeling Study of Binary Blend Compatibility of Polyamide 6 and Poly(vinyl acetate) with Different Degrees of Hydrolysis:  An Atomistic and Mesoscopic Approach

Spyriouni, Theodora; Vergelati, Caroll

doi:10.1021/ma001669t

Cited by 100 publications

(90 citation statements)

References 39 publications

(87 reference statements)

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“…This behavior is consistent with observed trends for solubility parameter calculations in polymeric systems. 95 Because the system volume at the Sastry point is calculated explicitly, the theory can also be used to determine the Sastry density. It is straightforward to show that the Sastry density predicted by this theory initially increases with chain length and then reaches a plateau value in the long-chain limit.…”

Section: Appendix A: Mean-field Theory For Cohesive Densitymentioning

confidence: 99%

Energy Landscape and Isotropic Tensile Strength of n-Alkane Glasses

2002

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We report results from a systematic simulational study of the ultimate mechanical strength of n-alkane glasses for carbon numbers n ) 1, 2, 3, 4, 6, 8, 16, 24, and 48. The ultimate isotropic tensile strength was determined by constructing the equation of state of energy landscape for this homologous series. The tensile strength depends nonmonotonically on carbon number, exhibiting a maximum at n ) 3. The mass density at which fracture occurs initially increases with chain length and then reaches a plateau value for n > 8. The predictions of the landscape equation of state are entirely consistent with results generated by a direct inherent structure deformation procedure. Although the ultimate isotropic tensile strength maximum at n ) 3 would seem to contradict physical intuition regarding chain entanglement, we present a simple mean-field theory that reveals the underlying physics responsible for the tensile strength maximum, namely the simple competition between intermolecular interactions and intramolecular packing effects.

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Section: Appendix A: Mean-field Theory For Cohesive Densitymentioning

confidence: 99%

Energy Landscape and Isotropic Tensile Strength of n-Alkane Glasses

2002

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confidence: 99%

“…14,19,20 Although most of the previous applications of the mesoscopic simulation are demonstrations for polymer systems with model parameters, it is applicable to a real system when a simulation parameter such as the Flory-Huggins χ-parameter for a coarse-grained model is determined for actual materials. 22,23 Several available methods for evaluating the χ-parameter for polymer-polymer, polymer-solvent, and solvent-solvent pairs in blend systems have already been proposed using an atomistic simulation based on the cohesive energy or the heat of mixing theory. [24][25][26][27][28][29] According to the synthesis process of the Nafion membrane in the case of a casting procedure, 13,30 the structure of the hydrated Nafion membrane seems to be spontaneously formed from solution in an alcohol and water mixture, in a way similar to the microphase separation of polymer mixture systems.…”

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confidence: 99%

A Computer Simulation Study of the Mesoscopic Structure of the Polyelectrolyte Membrane Nafion

Yamamoto

Hyodo

2003

Polym J

164

214

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ABSTRACT:We studied the mesoscopic structure of the perfluorinated sulfonic acid membrane Nafion containing water using a dissipative particle dynamics (DPD) simulation. A Nafion polymer is modeled by connecting coarsegrained particles, which correspond to the hydrophobic backbone of polytetrafluoroethylene and perfluorinated side chains terminated by hydrophilic end particles of sulfonic acid groups. Water is also modeled by the same size particle as adopted in the Nafion model, corresponding to a group of four H 2 O molecules. The Flory-Huggins χ-parameters between DPD particles are estimated from the mixing energy calculation using an atomistic simulation. In the DPD simulation, water particles and hydrophilic particles of Nafion side chains spontaneously form aggregates and are embedded in the hydrophobic phase of the Nafion backbone. This structure is a bicontinuous phase of Nafion and water regions and has a continuous path in the cavity of water in any direction. Although this sponge-like structure is essentially identical to the cluster-network model proposed from the experimental studies, the shape of the water clusters is not spherical but irregular, and the water regions are indistinguishable structures of water clusters and their channels. The cluster size and its dependence on the water content are in good agreement with experimental reports; therefore, the simulated mesoscopic structure is confirmed to be a highly possible one.KEY WORDS Computer Simulation / Dissipative Particle Dynamics / Polyelectrolyte Membrane / Mesoscopic Structure / Morphology / Nafion Membrane / Water Cluster / The well-known perfluorinated sulfonic acid membranes Nafion are the most common membrane materials used in the polymer electrolyte fuel cell because of their exceptional chemical, thermal and mechanical stability in addition to their reasonable proton conductivity. A Nafion polymer consists of a polytetrafluoroethylene backbone and perfluorinated pendant side chains terminated by sulfonic acid groups. The general molecular structure of Nafion polymer is 1where n is approximately 5-14, and m is 200-1000. To investigate the structure and swelling behavior of the hydrated Nafion membranes, numerous experimental efforts have been concentrated on neutron, wide and small angle X-ray scattering, infrared (IR) and Raman spectroscopy, and transmission electron microscopy (TEM) techniques. 1-13 It has been well established that hydrated Nafion membranes have two phases on a nanometer scale, a hydrophobic phase containing the backbone and a hydrophilic phase containing sulfonic acid groups and water. Several models for these structures such as the interconnected spherical water clusters (the cluster-network model) have been proposed for the interpretation of the scattering patterns. 1-7 However, these models are still under discussion concerning the size and shape of the water clusters. It is meaningful to clarify the structure of the membranes for analytical study and to improve the mechanical and transport properties of the m...

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“…We have verified that alternative estimations of χ based in the direct evaluation of the intermolecular energy between a pairs of units averaged over a statistical sample generated through Monte Carlo simulations [11] (as incorporated in the MS module "Blends") seem to be considerably less precise in the present mixture, depending largely on small details in the forcefield definitions. Similar large dependence on the potential details are found when χ is obtained from estimations of the cohesive energy density, or the solubility parameter [12], which can be directly evaluated form the MD simulations using an "Analysis" tool incorporated in the "Amorphous Cell" module.…”

Section: Introductionmentioning

confidence: 59%