Copolyimides with trifluoromethyl or methoxy substituents. NMR characterization

Pinel, Éliette; Bas, Corine; Neyertz, Sylvie; Albérola, N.; Pétiaud, Roger; Merçier, Régis

doi:10.1016/s0032-3861(02)00004-6

Cited by 19 publications

(33 citation statements)

References 16 publications

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“…Table 2 shows the average relaxed densities 〈F〉, which are all very close to the experimentally determined value of F exp ) 1.368 g cm -3 . [19][20][21] The average pressures of the simulation boxes, 〈p〉, prove that these densities correspond to atmospheric conditions. 〈F〉 for the 4150-atom systems is almost identical to F exp whereas the 6225-atom and 56025-atom systems fall within 0.7% of the experimental value.…”

Section: The Polyimide Packing Modelsmentioning

confidence: 95%

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Influence of System Size in Molecular Dynamics Simulations of Gas Permeation in Glassy Polymers

2004

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The dependence of gas permeation on system size in glassy polymers has been tested by creating several models containing different numbers of molecules of the same chain length for the ODPA-ODA homopolyimide and by subsequently determining the permeation characteristics of helium. Eight "standard size" 4150-atom, a 6225-atom, and a much more expensive computationally 56025-atom systems were generated using hybrid pivot Monte Carlo (PMC)-molecular dynamics (MD) single-chain sampling. Following the careful relaxation of the polyimide matrices, helium atoms were then inserted into these systems, and MD simulations were carried out at the same applied external conditions of constant temperature and pressure tensor. Average densities for the pure matrices all fell within 0.7% of the experimental value. Energetic and structural properties as well as solubilities and characterization of the void space were also found to be number independent, thus showing that the preparation procedure gives reproducible and reliable results. Helium diffusion was analyzed over periods up to 20 ns using different approaches, such as observation of the individual trajectories, mean-square displacements, distributions of penetrant displacements components, and van Hove correlation functions. No number dependence could be detected, whether the gas molecules were in the anomalous or in the Fickian regime.

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Section: The Polyimide Packing Modelsmentioning

confidence: 95%

“…When atom types i and j are different, the ij and σ ij cross-terms are obtained from the geometric mean of ii and jj and from the arithmetic mean of σ ii and σ jj . The electrostatic 19,20 U LJ (r) ) 4 ((σ/r) 12 -(σ/r) 6 ) (1) interactions were described by the Coulombic potential, U coul :…”

Section: Computational Detailsmentioning

confidence: 99%

Influence of System Size in Molecular Dynamics Simulations of Gas Permeation in Glassy Polymers

2004

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“…Al-Masri et al [10] prepared polyimide membranes from methyl-substituted diamine monomers and the gas permeation properties suggested that introduction of methyl groups into the polymer main chains created large free volume for gas transport. Pinel et al [11] synthesized polyimides with trifluoromethyl and methoxyl side groups, and studies showed that chain cohesion properties were decreased and the available void space for diffusion of gas molecules was increased by the trifluoromethyl substituents, but the methoxyl substituents did not show significant steric effects on gas permeations.…”

Section: Introductionmentioning

confidence: 99%

Synthetic 6FDA–ODA copolyimide membranes for gas separation and pervaporation: Functional groups and separation properties

Xiao

Huang

Feng

2007

Polymer

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“…Further 1 H-NMR spectra for trifluoromethyl groups containing copolyimides are given in the literature. [19] …”

Section: Materials Selectionmentioning

confidence: 99%

Cross‐linked Copolyimide Membranes for the Separation of Gaseous and Liquid Mixtures

Staudt-Bickel

2003

Soft Materials

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Cross-linked polymer structures gain increasing attention as membrane materials because they can fullfill the demands for industrial applications. Thereby, not only good separation characteristics but also high temperature stability and chemical resistancy are required. Furthermore, it is important that the membrane materials be plasticization resistant, because it is found that this causes strong increasing permeability with a drastic loss in selectivity. Plasticization effects occur with polyimide membranes in the presence of high CO 2 concentrations, hydrocarbons as propylene, propane, or aromatics. Unfortunately, these components are present in mixtures with high relevance being separated economically by membrane units or hybrid processes. In this article, the advantages of cross-linked 6FDA (4,4'hexafluoro isopropylidene diphthalic acid anhydride)-copolyimides are discussed based on experimental results for the separation of propylene/propane, benzene/cyclohexane, and high-pressure CO 2 /CH 4 mixtures. Additionally, opportunities for implementing the membrane units in conventional separation processes are discussed.

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Copolyimides with trifluoromethyl or methoxy substituents. NMR characterization

Cited by 19 publications

References 16 publications

Influence of System Size in Molecular Dynamics Simulations of Gas Permeation in Glassy Polymers

Influence of System Size in Molecular Dynamics Simulations of Gas Permeation in Glassy Polymers

Synthetic 6FDA–ODA copolyimide membranes for gas separation and pervaporation: Functional groups and separation properties

Cross‐linked Copolyimide Membranes for the Separation of Gaseous and Liquid Mixtures

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