Hyper-crosslinked, hybrid membranes via interfacial polymerization

Raaijmakers, Michiel J.T.

doi:10.3990/1.9789036539678

Cited by 3 publications

(15 citation statements)

References 12 publications

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“…New hybrid organic/inorganic membranes based on polyhedral oligomeric silsesquioxanes (POSS) covalently bonded with imides have recently been developed for gas separations applications under high-temperature and/or high-pressure conditions. [1][2][3][4][5] These polyPOSS-imide networks combine the molecular sieving abilities of polyimides 6 with the thermomechanical resistance of siloxane cages. 7 As such, they are able to perform under tougher operating conditions than the conventional polymer membranes used in gas separations.…”

Section: Introductionmentioning

confidence: 99%

“…Such hyper-cross-linked networks have been shown to exhibit different thermomechanical properties and molecular sieving capabilities depending on the nature of the dianhydride moiety. 1,2,4,11 Gas transport is known to occur through the organic part of the network 12 and permeance increases with the decrease in gas kinetic diameter, the increase in temperature and the increase in length of the imide bridge. However, short and rigid linkers such as those based on the pyromellitic dianhydride (PMDA) show similar apparent activation energies for the permeation of several gases, 2 while long and flexible linkers such as those based on the 4,4 0 -(hexafluoroisopropylidene) diphthalic anhydride (6FDA) display more of a spread in the various apparent gas activation energies.…”

Section: Introductionmentioning

confidence: 99%

“…It is also possible to use more elaborate coarse-graining approaches, 21,[44][45][46][47][48][49][50][51] but these are not necessary here as the formation of the network is rapid with respect to the diffusion of the reacting species through the forming membrane. 1,[3][4][5] Cross-linking can thus be carried out directly by fully-atomistic approaches. In addition, we specifically simulate the polyPOSS-(amic acid) cross-linking intermediate before transforming it into the final polyPOSS-imide form in order both to assess the effects of thermal imidization 3 and remain as close as possible to the experimental procedure.…”

Section: Introductionmentioning

confidence: 99%

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The influence of the dianhydride precursor in hyper-cross-linked hybrid polyPOSS-imide networks

Neyertz

Brown

Raaijmakers

et al. 2016

Phys. Chem. Chem. Phys.

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Hybrid organic/inorganic hyper-cross-linked membranes based on imides covalently bonded with polyhedral oligomeric silsesquioxanes (POSS) have recently been developed for gas-separation applications under high pressure and/or temperature conditions. Their molecular sieving capabilities have been shown to depend on the nature of the organic dianhydride precursor. In the present work, realistic molecular models of such polyPOSS-imide films based on the flexible 6FDA dianhydride are compared to those based on the shorter and more rigid PMDA dianhydride. The models creation procedure closely mimicks the mixing, polycondensation and imidization steps of the experimental scheme. The resulting networks are found to be highly heterogeneous in terms of both the number of links (from zero to the maximum possible of eight per POSS cage with an average of four) and their structure (interPOSS, intraPOSS, single-links, double-links) because of the eight-equivalent-arms nature of the POSS precursor. For both dianhydride precursors, crosslinking with POSS and the subsequent imidization step decrease the density, create additional void-space and increase the solubility of the resulting membranes. However, when compared to PMDA, the added flexibility of the central 6FDA bridge leads to a larger thermally-induced dilation of the networks and a larger volume loss per HO over the imidization step. With their better ability to redensify and to adapt to the added constraints, the cagecage distances and cage(organic bridge)cage angles in the 6FDA polyPOSS-imides span a larger range than in their PMDA counterparts. In addition, the stiffness of the PMDA moiety results in more unrelaxed free volume remaining trapped in the PMDA polyPOSS-imides upon imidization, and as such, to significantly more open structures with less favourable interactions. As expected from their enhanced flexibility, the thermomechanical properties of the 6FDA networks are slightly lower than those based on PMDA. However, the better mechanical resistance of PMDA over 6FDA does not really become significant before very large volume dilations.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The influence of the dianhydride precursor in hyper-cross-linked hybrid polyPOSS-imide networks

Neyertz

Brown

Raaijmakers

et al. 2016

Phys. Chem. Chem. Phys.

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“…When new materials are being developed, atomistic simulations, such as molecular dynamics (MD) and Monte Carlo (MC) calculations, can be used prior to experiments in order to pre-screen candidate structures under various operating conditions [ 51 , 52 , 53 , 54 ]. This is even more critical for high temperatures and pressures, since these are often difficult to implement in a laboratory and potentially hazardous [ 12 , 53 , 55 ]. In addition, mixed-gas measurements are much more complicated and time-consuming than pure-gas conditions [ 13 , 56 , 57 , 58 ].…”

Section: Introductionmentioning

confidence: 99%

Molecular Characterization of Membrane Gas Separation under Very High Temperatures and Pressure: Single- and Mixed-Gas CO2/CH4 and CO2/N2 Permselectivities in Hybrid Networks

et al. 2022

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This work illustrates the potential of using atomistic molecular dynamics (MD) and grand-canonical Monte Carlo (GCMC) simulations prior to experiments in order to pre-screen candidate membrane structures for gas separation, under harsh conditions of temperature and pressure. It compares at 300 °C and 400 °C the CO2/CH4 and CO2/N2 sieving properties of a series of hybrid networks based on inorganic silsesquioxanes hyper-cross-linked with small organic PMDA or 6FDA imides. The inorganic precursors are the octa(aminopropyl)silsesquioxane (POSS), which degrades above 300 °C, and the octa(aminophenyl)silsesquioxane (OAPS), which has three possible meta, para or ortho isomers and is expected to resist well above 400 °C. As such, the polyPOSS-imide networks were tested at 300 °C only, while the polyOAPS-imide networks were tested at both 300 °C and 400 °C. The feed gas pressure was set to 60 bar in all the simulations. The morphologies and densities of the pure model networks at 300 °C and 400 °C are strongly dependent on their precursors, with the amount of significant free volume ranging from ~2% to ~20%. Since measurements at high temperatures and pressures are difficult to carry out in a laboratory, six isomer-specific polyOAPS-imides and two polyPOSS-imides were simulated in order to assess their N2, CH4 and CO2 permselectivities under such harsh conditions. The models were first analyzed under single-gas conditions, but to be closer to the real processes, the networks that maintained CO2/CH4 and CO2/N2 ideal permselectivities above 2 were also tested with binary-gas 90%/10% CH4/CO2 and N2/CO2 feeds. At very high temperatures, the single-gas solubility coefficients vary in the same order as their critical temperatures, but the differences between the penetrants are attenuated and the plasticizing effect of CO2 is strongly reduced. The single-gas diffusion coefficients correlate well with the amount of available free volume in the matrices. Some OAPS-based networks exhibit a nanoporous behavior, while the others are less permeable and show higher ideal permselectivities. Four of the networks were further tested under mixed-gas conditions. The solubility coefficient improved for CO2, while the diffusion selectivity remained similar for the CO2/CH4 pair and disappeared for the CO2/N2 pair. The real separation factor is, thus, mostly governed by the solubility. Two polyOAPS-imide networks, i.e., the polyorthoOAPS-PMDA and the polymetaOAPS-6FDA, seem to be able to maintain their CO2/CH4 and CO2/N2 sieving abilities above 2 at 400 °C. These are outstanding performances for polymer-based membranes, and consequently, it is important to be able to produce isomer-specific polyOAPS-imides for use as gas separation membranes under harsh conditions.

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“…This allows for the subsequent synthesis efforts to only concentrate on the most promising ones. Furthermore, experiments under harsh conditions are difficult to implement and to interpret [35], whereas both MD and MC simulations can be carried out under a large variety of operating pressures and temperatures [36]. The present work represents the third stage in the detailed molecular characterization of polyPOSS/OAPS-imides.…”

Section: Introductionmentioning

confidence: 99%

Molecular characterization of polyOAPS-imide isomer hyper-cross-linked membranes: Free-volume morphologies and sorption isotherms for CH4 and CO2

Neyertz

Brown

Salimi

et al. 2021

Journal of Membrane Science

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Hyper-crosslinked, hybrid membranes via interfacial polymerization

Cited by 3 publications

References 12 publications

The influence of the dianhydride precursor in hyper-cross-linked hybrid polyPOSS-imide networks

The influence of the dianhydride precursor in hyper-cross-linked hybrid polyPOSS-imide networks

Molecular Characterization of Membrane Gas Separation under Very High Temperatures and Pressure: Single- and Mixed-Gas CO2/CH4 and CO2/N2 Permselectivities in Hybrid Networks

Molecular characterization of polyOAPS-imide isomer hyper-cross-linked membranes: Free-volume morphologies and sorption isotherms for CH4 and CO2

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