Ali Pournaghshband Isfahani

Plasticization resistant crosslinked polyurethane gas separation membranes

Polyurethanes (PUs) with good film formation ability and high gas separation properties are promising materials for gas separation membranes. However, low mechanical properties and high CO2 plasticization limit the industrial application of these membranes. Here, we synthesized a crosslinkable PU structure using a 1 : 3 : 2 molar ratio of Pluronic L61, isophorone diisocyanate (IPDI) and 3,5-diaminobenzoic acid (DABA). In order to improve both mechanical properties and plasticization resistance, a series of crosslinking agents with different chain lengths and functionalities were used to crosslink the PU via an esterification-based reaction. Pure (H2, CO2, N2, CH4, and C2H6) and mixed (CO2/N2 and CO2/CH4) gas permeability experiments were performed on the crosslinked PU (XPU) membranes. The XPU membranes showed enhanced mechanical properties and chemical stability and improved plasticization resistance to an extent about three times higher than the non-crosslinked PU and commercial membranes (PEBAX® 2533). Mechanical tests indicated an improvement of over 600% in Youngs modulus and 200% in hardness for XPUs compared to the pristine PU. The resulting crosslinked membranes with high CO2 separation performance (CO2/N2 ∼ 30) and superior thermal and mechanical properties are attractive candidates for industrial separation processes.

Pentiptycene-Based Polyurethane with Enhanced Mechanical Properties and CO2-Plasticization Resistance for Thin Film Gas Separation Membranes

The development of thin film composite (TFC) membranes offers an opportunity to achieve the permeability/selectivity requirements for optimum CO2 separation performance. However, the durability and performance of thin film gas separation membranes are mostly challenged by weak mechanical properties and high CO2 plasticization. Here, we designed new polyurethane (PU) structures with bulky aromatic chain extenders that afford preferred mechanical properties for ultra-thin-film formation. An improvement of about 1500% in Youngs modulus and 600% in hardness was observed for pentiptycene-based PUs compared to the typical PU membranes. Single (CO2, H2, CH4, and N2) and mixed (CO2/N2 and CO2/CH4) gas permeability tests were performed on the PU membranes. The resulting TFC membranes showed a high CO2 permeance up to 1400 GPU (10-6 cm3(STP) cm-2 s-1 cmHg-1) and the CO2/N2 and CO2/H2 selectivities of about 22 and 2.1, respectively. The enhanced mechanical properties of pentiptycene-based PUs result in high-performance thin membranes with the similar selectivity of the bulk polymer. The thin film membranes prepared from pentiptycene-based PUs also showed a twofold enhanced plasticization resistance compared to non-pentiptycene-containing PU membranes.

A facile synthesis of contorted spirobisindane-diamine and its microporous polyimides for gas separation

Microporous polyimides (PIM-PIs, KAUST-PIs) and polymers containing Trogers base (TB) derivatives with improved permeability and selectivity have great importance for separation of environmental gas pairs. Despite the tremendous progress in this field, facile synthesis of microporous polymers at the industrial scale via designing new monomers is still lacking. In this study, a new potential approach for large scale synthesis of spirobisindane diamine (DAS) (3) has been reported from commercially available 5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (TTSBI) and 3,4-difluoronitrobenzene. A series of DAS diamine based microporous polyimides were also synthesized. The resulting polymer membranes showed high mechanical and thermal properties with tunable gas separation performance.

Effect of Polyvinyl Alcohol Modified Silica Particles on the Physical and Gas Separation Properties of the Polyurethane Mixed Matrix Membranes

Silicon based particles were prepared using tetraethoxysilane (TEOS) as a silica monomer, and low concentration of polyethylene oxide-polypropylene oxide block copolymer (pluronic) with polyvinyl alcohol (PVA) as templating agents. The synthesized particles showed higher polarity compare with conventional silica particles. PU/silica mixed matrix membranes (MMMs) were prepared by solution casting technique. The membranes were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and differential scanning calorimetry (DSC). FT-IR result confirmed the existence of PVA in the final structure of the synthesized silica network. The SEM micrographs indicated an appropriate distribution of silica particles in the polymer matrix. Gas transport properties of membranes were studied for pure CO2, CH4, O2 and N2 gases at 10 bar and 25 ∘C. The results showed that the permeabilities of CH4 and CO2 enhanced whereas that of other gases decreased with increasing the modified silica contents. In the membrane with 10 wt.% silica content, an enhancement of CO2/CH4 (α ≈ 7.7) and CO2/N2 (α ≈ 91.4) selectivities was observed.

Tuning the Gas Selectivity of Tröger's Base Polyimide Membranes by Using Carboxylic Acid and Tertiary Base Interactions

Polyimide-based materials provide attractive chemistries for the development of gas-separation membranes. Modification of inter- and intra-chain interactions is a route to improve the separation performance. In this work, copolyimides with Trögers base (TB) monomers are designed and synthesized. In particular, a series of copolyimides is synthesized with different contents of carboxylic acid groups (0-50 wt %) to alter the inter- and intra-chain interactions and enhance the basicity of the TB-polyimides. A detailed thermal and structural analysis is provided for the new copolyimides. Gas permeation data reveal a tunable trend in separation performance with increasing carboxylic acid group content. Importantly, this is one of the few examples of copolyimide membranes materials that show enhanced plasticization resistance to high-pressure gas feeds through physical cross-linking.