Bader Ghanem - Academia.edu (original) (raw)

Papers by Bader Ghanem

Aps March Meeting Abstracts, Mar 21, 2011

Like polymers of intrinsic microporosity (PIMs), organic molecules of intrinsic microporosity (OM... more Like polymers of intrinsic microporosity (PIMs), organic molecules of intrinsic microporosity (OMIMs) are glassy solids featuring a large concentration of pores smaller than 2 nm and large internal surface area as measured by gas sorption experiments. OMIMs are oligomers designed to fill space inefficiently, consisting of several rigid segments joined at one vertex to produce concave faces. Both X-ray scattering patterns and simulations provide insight into the packing geometry and short-range order of these molecules. We also discuss the interpretation of scattering patterns from two- and three-dimensional network PIMs. Supported by NSF/Materials World Network/EPSRC and the NSF Graduate Research Fellowship Program.

Polymers of Intrinsic Microporosity (PIMs) possess microporosity because they have rigid, contort... more Polymers of Intrinsic Microporosity (PIMs) possess microporosity because they have rigid, contorted mol. structures that cannot pack efficiently. They can be prepd. either as insol. network materials or sol. polymers that may be pptd. from soln. as powders or cast into a membrane form (e.g. PIM-1). Unlike common microporous materials (e.g. activated carbons, zeolites) it is straightforward to tailor the chem. nature of PIMs to design materials for chemoselective processes. The unique structure and processability of PIMs makes them attractive for a no. of applications including heterogeneous catalysis, gas sepn. membranes, water purifn. and hydrogen storage. The potential diversity of structure, as controlled by the choice of monomer, will allow the synthesis of PIMs specifically designed for each application. This talk will discuss some of the synthetic aspects behind PIM technol. including the occurrence of branching and cyclic oligomer formation, scale-up considerations and novel ...

Journal of Membrane Science, 2015

Solution-processable polyimides of intrinsic microporosity (PIM-PIs) comprising relatively inflex... more Solution-processable polyimides of intrinsic microporosity (PIM-PIs) comprising relatively inflexible and contorted backbones have demonstrated outstanding molecular-sieving behavior in membrane-based separation of gas/gas pairs. In this work, the effects of systematically increasing intra-chain rigidity on the propylene/propane separation properties were compared for PIM-PIs made from 2,3,5,6-tetramethyl-1,4-phenylene diamine (TMPD) and (i) spiro-centered dianhyride (SPDA-TMPD or PIM-PI-1) and (ii) 9,10

ChemInform, 1991

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Journal of Membrane Science, 2015

ABSTRACT The synthesis and gas permeation properties of two 6FDA-dianhydride-based polyimides pre... more ABSTRACT The synthesis and gas permeation properties of two 6FDA-dianhydride-based polyimides prepared from 2,6-diaminotriptycene (6FDA-DAT1) and its extended iptycene analog (6FDA-DAT2) are reported. The additional benzene ring on the extended triptycene moiety in 6FDA-DAT2 increases the free volume over 6FDA-DAT1 and reduces the chain packing efficiency. The BET surface area based on nitrogen adsorption in 6FDA-DAT2 (450 m2g−1) is ~40% greater than that of 6FDA-DAT1 (320 m2g−1). 6FDA-DAT1 shows a CO2 permeability of 120 Barrer and CO2/CH4 selectivity of 38, whereas 6FDA-DAT2 exhibits a 75% increase in CO2 permeability to 210 Barrer coupled with a moderate decrease in selectivity (CO2/CH4=30). Interestingly, minimal physical aging was observed over 150 days for both polymers and attributed to the high internal free volume of the shape-persistent iptycene geometries. The aged polyimides maintained CO2/CH4 selectivities of 25-35 along with high CO2 permeabilities of 90-120 Barrer up to partial CO2 pressures of 10 bar of an aggressive 50:50 CO2:CH4 mixed-gas feed, suggesting potential application in membranes for natural gas sweetening.

ACS Macro Letters, 2015

A novel generic method is reported for the synthesis of a spirobifluorene-based dianhydride (SBFD... more A novel generic method is reported for the synthesis of a spirobifluorene-based dianhydride (SBFDA). An intrinsically microporous polyimide was obtained by polycondensation reaction with 3,3′-dimethylnaphthidine (DMN). The corresponding polymer (SBFDA-DMN) exhibited good solubility, excellent thermal stability, as well as significant microporosity with high BET surface area of 686 m 2 /g. The O 2 permeability of a methanol-treated and air-dried membrane was 1193 Barrer with a moderate O 2 /N 2 selectivity of 3.2. The post-treatment history and aging conditions had great effects on the membrane performance. A significant drop in permeability coupled with an increase in selectivity was observed after long-term aging. After storage of 200 days, the gas separation properties of SBFDA-DMN were located slightly above the latest Robeson upper bounds for several gas pairs such as O 2 /N 2 and H 2 /N 2 .

Journal of Membrane Science, 2015

A sub-T g thermally-annealed (250 1C, 24 h) ultra-microporous PIM-polyimide bearing a 9,10-diisop... more A sub-T g thermally-annealed (250 1C, 24 h) ultra-microporous PIM-polyimide bearing a 9,10-diisopropyltriptycene contortion center and hydroxyl-functionalized diamine (2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, APAF) exhibited plasticization resistance up to 50 bar for a 1:1 CO 2 /CH 4 feed mixture, with a 9-fold higher CO 2 permeability (30 Barrer) and 2-fold increase in CO 2 /CH 4 permselectivity ( $ 50) over conventional dense cellulose acetate membranes at 10 bar CO 2 partial pressure. Interestingly, mixed-gas CO 2 /CH 4 permselectivities were 10-20% higher than those evaluated under pure-gas conditions due to reduction of mixed-gas CH 4 permeability by co-permeation of CO 2 . Gas transport, physisorption and fluorescence studies indicated a sieving pore-structure engaged in interchain charge transfer complexes (CTCs), similar to that of low-free-volume 6FDA-APAF polyimide. The isosteric heat of adsorption of CO 2 as well as CO 2 /CH 4 solubility selectivities varied negligibly upon replacement of OH with CH 3 but CTC formation was hindered, CO 2 sorption increased, CO 2 permeability increased $ 3-fold, CO 2 /CH 4 permselectivity dropped to $ 30 and CH 4 mixed-gas co-permeation increased. These results suggest that hydroxyl-functionalization did not cause preferential polymergas interactions but primarily elicited diffusion-dominated changes owing to a tightened microstructure more resistant to CO 2 -induced dilations. Solution-processable hydroxyl-functionalized PIM-type polyimides provide a new platform of advanced materials that unites the high selectivities of low-freevolume polymers with the high permeabilities of PIM-type materials particularly for natural gas sweetening applications.

Macromolecules, 2014

Based on high-pressure pure-and mixed-gas (50:50) CO 2 / CH 4 separation properties of two intrin... more Based on high-pressure pure-and mixed-gas (50:50) CO 2 / CH 4 separation properties of two intrinsically microporous triptycene-based polyimides (TPDA−TMPD and TPDA−6FpDA), the intrachain rigidity central to "conventional PIM" design principles is not a singular solution to intrinsic plasticization resistance. Despite the significant intrachain rigidity in TPDA−TMPD, a 300% increase in P MIX (CH 4 ), 50% decrease in α(CO 2 / CH 4 ) from 24 to 12, and continuous increase in P MIX (CO 2 ) occurred from 4 to 30 bar. On the other hand, the more flexible and densely packed TPDA− 6FpDA exhibited a slight upturn in P MIX (CO 2 ) at 20 bar similar to a dense cellulose acetate (CA) film, also reported here, despite a 4-fold higher CO 2 sorption capacity. Microstructural investigations suggest that the interconnected O 2 -and H 2 -sieving ultramicroporosity of TPDA−TMPD is more sensitive to slight CO 2 -induced dilations and is the physical basis for a more extensive and accelerated plasticization. Interchain rigidity, potentially by interchain interactions, is emphasized and may be facilitated by intrachain mobility.

Macromolecules, 2014

Highly ultramicroporous, solution-processable polyimides bearing 9,10-bridgehead-substituted trip... more Highly ultramicroporous, solution-processable polyimides bearing 9,10-bridgehead-substituted triptycene demonstrated the highest BET surface area reported for polyimides (840 m 2 g −1 ) and several new highs in gas selectivity and permeability for hydrogen (1630−3980 barrers, H 2 /CH 4 ∼ 38) and air (230−630 barrers, O 2 /N 2 = 5.5−5.9) separations. Two new dianhydrides bearing 9,10-diethyl-and 9,10-dipropyltriptycenes indicate that the ultramicroporosity is optimized for fast polymeric sieving with the use of short, bulky isopropyl bridgeheads and methyl-substituted diamines (TrMPD, TMPD, and TMBZ) that increase intrachain rigidity. Mechanically, the triptycene-based analogue of a spirobisindanebased polyimide exhibited 50% increases in both tensile strength at break (94 MPa) and elastic modulus (2460 MPa) with corresponding 90% lower elongations at break (6%) likely due to the ability of highly entangled spiro-based chains to unwind. To guide future polyimide design, structure/property relationships are suggested between the geometry of the contortion center, the diamine and bridgehead substituent, and the mechanical, microstructural, and gas transport properties.

Advanced Materials, 2014

O 2 /N 2 separation. Triptycene, the simplest member of the iptycenes, has three benzene arms bri... more O 2 /N 2 separation. Triptycene, the simplest member of the iptycenes, has three benzene arms bridged about a [2,2,2]-tricyclic ring system in a shape-persistent, 3D paddlewheel confi guration that locks in "internal molecular free volume" (IMFV) between the rings. 9,10-bridgehead substitution can augment the overall rigidity and bulkiness of triptycene. Subsequent incorporation into rigid backbones has produced highly sorbing network polymers and our highly sieving solutionprocessable polyimides. However, polyimides retain an additional degree of fl exibility at the imide bond, which may compromise microporosity and selectivity by sacrifi cing intramolecular rigidity. It is of great interest to evaluate more rigid fused-ring ladder backbones free of the fl exible single bonds of PIM-PIs and the traditional spiro-center employed in PIMs (i.e., single tetrahedral carbon atom shared by two rings). Several soluble triptycene-bearing ladder polymers have beensynthesized before, 19, but none of the investigations addressed the importance of 9,10-bridgehead substituents for gas separation performance. Our recent work on PIM-PIs has established that 9,10-bridgehead substitution of the triptycene can result in signifi cant gains in permeability and selectivity. The integration of 9,10-dialkyl-substituted triptycene into a soluble ladder PIM was successfully demonstrated by self-polycondensation of a novel A-B monomer bearing a 9,10-dibutyl-substituted triptycene and both phenazine-activating o -dichloride and catechol groups. Self-polymerization of such A-B monomers has a signifi cant advantage in stepgrowth polymerization over previously used AA-BB monomers because high molecular weight fi lm-forming products can be achieved without strict control of the stoichiometric balance. Accordingly, this Communication describes the synthesis, microstructures, and exceptional gas transport properties of two new soluble ladder polymers -TPIM-1 and TPIM-2 -containing triptycene moieties substituted with branched isopropyl and linear propyl chains at the 9,10-bridgeheads. The precursor A-B monomers were modifi ed with an o -difl uoride functionality for enhanced activation for nucleophilic aromatic substitution. Technologically attractive selectivity-driven performance signifi cantly transcending the upper bounds is observed for hydrogen and air separations, accounting for about 75% of the membrane-based gas separation business, as well as emerging biogas and natural gas (CO 2 /CH 4 ) applications.

Toxicological & Environmental Chemistry, 1990

In this paper we report the isolation of an unexpected product from the condensation of α‐methylc... more In this paper we report the isolation of an unexpected product from the condensation of α‐methylcinnamaldehyde with arylacetonitriles using sodium ethoxide at room temperature, 2,6‐Diaryl‐4‐methyl‐5‐phenyl‐2‐heptenedinitriles were obtained as a result of a 1,4 and 1,2‐addition of the arylacetonitriles enolate at the carbon‐carbon double bond and the carbonyl group of the α,β‐Michael acceptors. The reaction products were identified on the basis

Toxicological & Environmental Chemistry, 1990

The condensation of substituted cinnamaldehydes and arylacetonitriles using sodium ethoxide in et... more The condensation of substituted cinnamaldehydes and arylacetonitriles using sodium ethoxide in ethanol at room temperature afforded 2,5‐diaryl‐2,4‐pentadienenitriles in good yield. The structure of the reaction products was established on the basis of their infrared, nuclear magnetic resonance and elemental analysis data. Two representative compounds were studied for their mutagenic activity. One of them showed a weak mutagenicity while the second

Tetrahedron Letters, 2004

A novel unsymmetrically substituted phthalocyanine, which contains an extended planar core and a ... more A novel unsymmetrically substituted phthalocyanine, which contains an extended planar core and a pair of adjacent peripheral hydroxyl groups is synthesised and used to prepare planar phthalocyanine oligomers. These materials act as macrodiscotic liquid crystals giving a columnar mesophase, which is stable over a large temperature range.

Tetrahedron, 1989

1,~Diaryl-2-proper+l-ones react with ethyl cysnoacetate in presence of sodlm ethoxide at rmn temp... more 1,~Diaryl-2-proper+l-ones react with ethyl cysnoacetate in presence of sodlm ethoxide at rmn temperature to give 2-sroyl-1,3,5-triaryl-4-csrbethoxy-4-cysnocyclohexanols. The structure of the reaction products was established by infrared, R-1 and C-13 nuclear magnetic resonance spectral data as well as elemental snalysls. X-ray crystallography shows the presence of the cyclohexanol maeity.

Synthesis, 1992

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis, 1990

2, 4, 6-Triaryl-3-aroyl-4-hydroxy-1, 1-cyclohexanedicarbonitriles have been prepared by the base-... more 2, 4, 6-Triaryl-3-aroyl-4-hydroxy-1, 1-cyclohexanedicarbonitriles have been prepared by the base-catalyzed reaction of variously substituted α, β-unsaturated ketones with malononitrile in anhydrous ether at room temperature. Their structures have been established on the ...

Physical Chemistry Chemical Physics, 2007

The challenge of storing hydrogen at high volumetric and gravimetric density for automotive appli... more The challenge of storing hydrogen at high volumetric and gravimetric density for automotive applications has prompted investigations into the potential of cryo-adsorption on the internal surface area of microporous organic polymers. A range of Polymers of Intrinsic Microporosity (PIMs) has been studied, the best PIM to date (a network-PIM incorporating a triptycene subunit) taking up 2.7% H(2) by mass at 10 bar/77 K. HyperCrosslinked Polymers (HCPs) also show promising performance as H(2) storage materials, particularly at pressures >10 bar. The N(2) and H(2) adsorption behaviour at 77 K of six PIMs and a HCP are compared. Surface areas based on Langmuir plots of H(2) adsorption at high pressure are shown to provide a useful guide to hydrogen capacity, but Langmuir plots based on low pressure data underestimate the potential H(2) uptake. The micropore distribution influences the form of the H(2) isotherm, a higher concentration of ultramicropores (pore size <0.7 nm) being associated with enhanced low pressure adsorption.

physica status solidi (RRL) – Rapid Research Letters, 2007

The performance of polymeric membranes for gas separation is mainly determined by the free volume... more The performance of polymeric membranes for gas separation is mainly determined by the free volume. Polymers of intrinsic microporosity are interesting due to the high abundance o f accessible free volume. We performed measurements of the temperature dependence of the positron lifetime, generally accepted for investigation of free volume, in two polymers o f intrinsic microporosity (PIM-1 and PIM-7) in the range from 143 to 523 K. The mean value of the free volume calculated from the ortho-positronium lifetime is in the range of typical values for high free volume polymers. However, the temperature dependence of the local free volume is non-monotonous in contrast to the macroscopic thermal expansion. The explanation is linked to the spirocenters in the polymer.

Aps March Meeting Abstracts, Mar 21, 2011

Like polymers of intrinsic microporosity (PIMs), organic molecules of intrinsic microporosity (OM... more Like polymers of intrinsic microporosity (PIMs), organic molecules of intrinsic microporosity (OMIMs) are glassy solids featuring a large concentration of pores smaller than 2 nm and large internal surface area as measured by gas sorption experiments. OMIMs are oligomers designed to fill space inefficiently, consisting of several rigid segments joined at one vertex to produce concave faces. Both X-ray scattering patterns and simulations provide insight into the packing geometry and short-range order of these molecules. We also discuss the interpretation of scattering patterns from two- and three-dimensional network PIMs. Supported by NSF/Materials World Network/EPSRC and the NSF Graduate Research Fellowship Program.

Polymers of Intrinsic Microporosity (PIMs) possess microporosity because they have rigid, contort... more Polymers of Intrinsic Microporosity (PIMs) possess microporosity because they have rigid, contorted mol. structures that cannot pack efficiently. They can be prepd. either as insol. network materials or sol. polymers that may be pptd. from soln. as powders or cast into a membrane form (e.g. PIM-1). Unlike common microporous materials (e.g. activated carbons, zeolites) it is straightforward to tailor the chem. nature of PIMs to design materials for chemoselective processes. The unique structure and processability of PIMs makes them attractive for a no. of applications including heterogeneous catalysis, gas sepn. membranes, water purifn. and hydrogen storage. The potential diversity of structure, as controlled by the choice of monomer, will allow the synthesis of PIMs specifically designed for each application. This talk will discuss some of the synthetic aspects behind PIM technol. including the occurrence of branching and cyclic oligomer formation, scale-up considerations and novel ...

Journal of Membrane Science, 2015

Solution-processable polyimides of intrinsic microporosity (PIM-PIs) comprising relatively inflex... more Solution-processable polyimides of intrinsic microporosity (PIM-PIs) comprising relatively inflexible and contorted backbones have demonstrated outstanding molecular-sieving behavior in membrane-based separation of gas/gas pairs. In this work, the effects of systematically increasing intra-chain rigidity on the propylene/propane separation properties were compared for PIM-PIs made from 2,3,5,6-tetramethyl-1,4-phenylene diamine (TMPD) and (i) spiro-centered dianhyride (SPDA-TMPD or PIM-PI-1) and (ii) 9,10

ChemInform, 1991

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Journal of Membrane Science, 2015

ABSTRACT The synthesis and gas permeation properties of two 6FDA-dianhydride-based polyimides pre... more ABSTRACT The synthesis and gas permeation properties of two 6FDA-dianhydride-based polyimides prepared from 2,6-diaminotriptycene (6FDA-DAT1) and its extended iptycene analog (6FDA-DAT2) are reported. The additional benzene ring on the extended triptycene moiety in 6FDA-DAT2 increases the free volume over 6FDA-DAT1 and reduces the chain packing efficiency. The BET surface area based on nitrogen adsorption in 6FDA-DAT2 (450 m2g−1) is ~40% greater than that of 6FDA-DAT1 (320 m2g−1). 6FDA-DAT1 shows a CO2 permeability of 120 Barrer and CO2/CH4 selectivity of 38, whereas 6FDA-DAT2 exhibits a 75% increase in CO2 permeability to 210 Barrer coupled with a moderate decrease in selectivity (CO2/CH4=30). Interestingly, minimal physical aging was observed over 150 days for both polymers and attributed to the high internal free volume of the shape-persistent iptycene geometries. The aged polyimides maintained CO2/CH4 selectivities of 25-35 along with high CO2 permeabilities of 90-120 Barrer up to partial CO2 pressures of 10 bar of an aggressive 50:50 CO2:CH4 mixed-gas feed, suggesting potential application in membranes for natural gas sweetening.

ACS Macro Letters, 2015

A novel generic method is reported for the synthesis of a spirobifluorene-based dianhydride (SBFD... more A novel generic method is reported for the synthesis of a spirobifluorene-based dianhydride (SBFDA). An intrinsically microporous polyimide was obtained by polycondensation reaction with 3,3′-dimethylnaphthidine (DMN). The corresponding polymer (SBFDA-DMN) exhibited good solubility, excellent thermal stability, as well as significant microporosity with high BET surface area of 686 m 2 /g. The O 2 permeability of a methanol-treated and air-dried membrane was 1193 Barrer with a moderate O 2 /N 2 selectivity of 3.2. The post-treatment history and aging conditions had great effects on the membrane performance. A significant drop in permeability coupled with an increase in selectivity was observed after long-term aging. After storage of 200 days, the gas separation properties of SBFDA-DMN were located slightly above the latest Robeson upper bounds for several gas pairs such as O 2 /N 2 and H 2 /N 2 .

Journal of Membrane Science, 2015

A sub-T g thermally-annealed (250 1C, 24 h) ultra-microporous PIM-polyimide bearing a 9,10-diisop... more A sub-T g thermally-annealed (250 1C, 24 h) ultra-microporous PIM-polyimide bearing a 9,10-diisopropyltriptycene contortion center and hydroxyl-functionalized diamine (2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, APAF) exhibited plasticization resistance up to 50 bar for a 1:1 CO 2 /CH 4 feed mixture, with a 9-fold higher CO 2 permeability (30 Barrer) and 2-fold increase in CO 2 /CH 4 permselectivity ( $ 50) over conventional dense cellulose acetate membranes at 10 bar CO 2 partial pressure. Interestingly, mixed-gas CO 2 /CH 4 permselectivities were 10-20% higher than those evaluated under pure-gas conditions due to reduction of mixed-gas CH 4 permeability by co-permeation of CO 2 . Gas transport, physisorption and fluorescence studies indicated a sieving pore-structure engaged in interchain charge transfer complexes (CTCs), similar to that of low-free-volume 6FDA-APAF polyimide. The isosteric heat of adsorption of CO 2 as well as CO 2 /CH 4 solubility selectivities varied negligibly upon replacement of OH with CH 3 but CTC formation was hindered, CO 2 sorption increased, CO 2 permeability increased $ 3-fold, CO 2 /CH 4 permselectivity dropped to $ 30 and CH 4 mixed-gas co-permeation increased. These results suggest that hydroxyl-functionalization did not cause preferential polymergas interactions but primarily elicited diffusion-dominated changes owing to a tightened microstructure more resistant to CO 2 -induced dilations. Solution-processable hydroxyl-functionalized PIM-type polyimides provide a new platform of advanced materials that unites the high selectivities of low-freevolume polymers with the high permeabilities of PIM-type materials particularly for natural gas sweetening applications.

Macromolecules, 2014

Based on high-pressure pure-and mixed-gas (50:50) CO 2 / CH 4 separation properties of two intrin... more Based on high-pressure pure-and mixed-gas (50:50) CO 2 / CH 4 separation properties of two intrinsically microporous triptycene-based polyimides (TPDA−TMPD and TPDA−6FpDA), the intrachain rigidity central to "conventional PIM" design principles is not a singular solution to intrinsic plasticization resistance. Despite the significant intrachain rigidity in TPDA−TMPD, a 300% increase in P MIX (CH 4 ), 50% decrease in α(CO 2 / CH 4 ) from 24 to 12, and continuous increase in P MIX (CO 2 ) occurred from 4 to 30 bar. On the other hand, the more flexible and densely packed TPDA− 6FpDA exhibited a slight upturn in P MIX (CO 2 ) at 20 bar similar to a dense cellulose acetate (CA) film, also reported here, despite a 4-fold higher CO 2 sorption capacity. Microstructural investigations suggest that the interconnected O 2 -and H 2 -sieving ultramicroporosity of TPDA−TMPD is more sensitive to slight CO 2 -induced dilations and is the physical basis for a more extensive and accelerated plasticization. Interchain rigidity, potentially by interchain interactions, is emphasized and may be facilitated by intrachain mobility.

Macromolecules, 2014

Highly ultramicroporous, solution-processable polyimides bearing 9,10-bridgehead-substituted trip... more Highly ultramicroporous, solution-processable polyimides bearing 9,10-bridgehead-substituted triptycene demonstrated the highest BET surface area reported for polyimides (840 m 2 g −1 ) and several new highs in gas selectivity and permeability for hydrogen (1630−3980 barrers, H 2 /CH 4 ∼ 38) and air (230−630 barrers, O 2 /N 2 = 5.5−5.9) separations. Two new dianhydrides bearing 9,10-diethyl-and 9,10-dipropyltriptycenes indicate that the ultramicroporosity is optimized for fast polymeric sieving with the use of short, bulky isopropyl bridgeheads and methyl-substituted diamines (TrMPD, TMPD, and TMBZ) that increase intrachain rigidity. Mechanically, the triptycene-based analogue of a spirobisindanebased polyimide exhibited 50% increases in both tensile strength at break (94 MPa) and elastic modulus (2460 MPa) with corresponding 90% lower elongations at break (6%) likely due to the ability of highly entangled spiro-based chains to unwind. To guide future polyimide design, structure/property relationships are suggested between the geometry of the contortion center, the diamine and bridgehead substituent, and the mechanical, microstructural, and gas transport properties.

Advanced Materials, 2014

O 2 /N 2 separation. Triptycene, the simplest member of the iptycenes, has three benzene arms bri... more O 2 /N 2 separation. Triptycene, the simplest member of the iptycenes, has three benzene arms bridged about a [2,2,2]-tricyclic ring system in a shape-persistent, 3D paddlewheel confi guration that locks in "internal molecular free volume" (IMFV) between the rings. 9,10-bridgehead substitution can augment the overall rigidity and bulkiness of triptycene. Subsequent incorporation into rigid backbones has produced highly sorbing network polymers and our highly sieving solutionprocessable polyimides. However, polyimides retain an additional degree of fl exibility at the imide bond, which may compromise microporosity and selectivity by sacrifi cing intramolecular rigidity. It is of great interest to evaluate more rigid fused-ring ladder backbones free of the fl exible single bonds of PIM-PIs and the traditional spiro-center employed in PIMs (i.e., single tetrahedral carbon atom shared by two rings). Several soluble triptycene-bearing ladder polymers have beensynthesized before, 19, but none of the investigations addressed the importance of 9,10-bridgehead substituents for gas separation performance. Our recent work on PIM-PIs has established that 9,10-bridgehead substitution of the triptycene can result in signifi cant gains in permeability and selectivity. The integration of 9,10-dialkyl-substituted triptycene into a soluble ladder PIM was successfully demonstrated by self-polycondensation of a novel A-B monomer bearing a 9,10-dibutyl-substituted triptycene and both phenazine-activating o -dichloride and catechol groups. Self-polymerization of such A-B monomers has a signifi cant advantage in stepgrowth polymerization over previously used AA-BB monomers because high molecular weight fi lm-forming products can be achieved without strict control of the stoichiometric balance. Accordingly, this Communication describes the synthesis, microstructures, and exceptional gas transport properties of two new soluble ladder polymers -TPIM-1 and TPIM-2 -containing triptycene moieties substituted with branched isopropyl and linear propyl chains at the 9,10-bridgeheads. The precursor A-B monomers were modifi ed with an o -difl uoride functionality for enhanced activation for nucleophilic aromatic substitution. Technologically attractive selectivity-driven performance signifi cantly transcending the upper bounds is observed for hydrogen and air separations, accounting for about 75% of the membrane-based gas separation business, as well as emerging biogas and natural gas (CO 2 /CH 4 ) applications.

Toxicological & Environmental Chemistry, 1990

In this paper we report the isolation of an unexpected product from the condensation of α‐methylc... more In this paper we report the isolation of an unexpected product from the condensation of α‐methylcinnamaldehyde with arylacetonitriles using sodium ethoxide at room temperature, 2,6‐Diaryl‐4‐methyl‐5‐phenyl‐2‐heptenedinitriles were obtained as a result of a 1,4 and 1,2‐addition of the arylacetonitriles enolate at the carbon‐carbon double bond and the carbonyl group of the α,β‐Michael acceptors. The reaction products were identified on the basis

Toxicological & Environmental Chemistry, 1990

The condensation of substituted cinnamaldehydes and arylacetonitriles using sodium ethoxide in et... more The condensation of substituted cinnamaldehydes and arylacetonitriles using sodium ethoxide in ethanol at room temperature afforded 2,5‐diaryl‐2,4‐pentadienenitriles in good yield. The structure of the reaction products was established on the basis of their infrared, nuclear magnetic resonance and elemental analysis data. Two representative compounds were studied for their mutagenic activity. One of them showed a weak mutagenicity while the second

Tetrahedron Letters, 2004

A novel unsymmetrically substituted phthalocyanine, which contains an extended planar core and a ... more A novel unsymmetrically substituted phthalocyanine, which contains an extended planar core and a pair of adjacent peripheral hydroxyl groups is synthesised and used to prepare planar phthalocyanine oligomers. These materials act as macrodiscotic liquid crystals giving a columnar mesophase, which is stable over a large temperature range.

Tetrahedron, 1989

1,~Diaryl-2-proper+l-ones react with ethyl cysnoacetate in presence of sodlm ethoxide at rmn temp... more 1,~Diaryl-2-proper+l-ones react with ethyl cysnoacetate in presence of sodlm ethoxide at rmn temperature to give 2-sroyl-1,3,5-triaryl-4-csrbethoxy-4-cysnocyclohexanols. The structure of the reaction products was established by infrared, R-1 and C-13 nuclear magnetic resonance spectral data as well as elemental snalysls. X-ray crystallography shows the presence of the cyclohexanol maeity.

Synthesis, 1992

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis, 1990

2, 4, 6-Triaryl-3-aroyl-4-hydroxy-1, 1-cyclohexanedicarbonitriles have been prepared by the base-... more 2, 4, 6-Triaryl-3-aroyl-4-hydroxy-1, 1-cyclohexanedicarbonitriles have been prepared by the base-catalyzed reaction of variously substituted α, β-unsaturated ketones with malononitrile in anhydrous ether at room temperature. Their structures have been established on the ...

Physical Chemistry Chemical Physics, 2007

The challenge of storing hydrogen at high volumetric and gravimetric density for automotive appli... more The challenge of storing hydrogen at high volumetric and gravimetric density for automotive applications has prompted investigations into the potential of cryo-adsorption on the internal surface area of microporous organic polymers. A range of Polymers of Intrinsic Microporosity (PIMs) has been studied, the best PIM to date (a network-PIM incorporating a triptycene subunit) taking up 2.7% H(2) by mass at 10 bar/77 K. HyperCrosslinked Polymers (HCPs) also show promising performance as H(2) storage materials, particularly at pressures >10 bar. The N(2) and H(2) adsorption behaviour at 77 K of six PIMs and a HCP are compared. Surface areas based on Langmuir plots of H(2) adsorption at high pressure are shown to provide a useful guide to hydrogen capacity, but Langmuir plots based on low pressure data underestimate the potential H(2) uptake. The micropore distribution influences the form of the H(2) isotherm, a higher concentration of ultramicropores (pore size <0.7 nm) being associated with enhanced low pressure adsorption.

physica status solidi (RRL) – Rapid Research Letters, 2007

The performance of polymeric membranes for gas separation is mainly determined by the free volume... more The performance of polymeric membranes for gas separation is mainly determined by the free volume. Polymers of intrinsic microporosity are interesting due to the high abundance o f accessible free volume. We performed measurements of the temperature dependence of the positron lifetime, generally accepted for investigation of free volume, in two polymers o f intrinsic microporosity (PIM-1 and PIM-7) in the range from 143 to 523 K. The mean value of the free volume calculated from the ortho-positronium lifetime is in the range of typical values for high free volume polymers. However, the temperature dependence of the local free volume is non-monotonous in contrast to the macroscopic thermal expansion. The explanation is linked to the spirocenters in the polymer.