Superhydrophobic Hexamethylene Diisocyanate Modified Hydrolyzed Polymers of Intrinsic Microporosity Electrospun Ultrafine Fibrous Membrane for the Adsorption of Organic Compounds and Oil/Water Separation

WOS: 000461400500024Polymers of intrinsic microporosity (PIMs) have gained significant research interest because of their successful applications in adsorption and separation. PIM-1 is the first and most studied member of this class because it shows specific interactions with some certain organic species. Chemical modification of PIM-1, which can be achieved by simply hydrolyzing the nitrile groups in the backbone, provides an advantage of tailoring its adsorption and separation performances. In this study, electrospinning of ultrafine fibers from hydrolyzed polymer of intrinsic microporosity (HPIM) and blends of hexamethylene diisocyanate (HMDI)/HPIM was achieved in several different ratios of HMDI/HPIM ranging from 1:9 to 1:1 (w/w). Bead-free and uniform fibers were obtained in the form of self-standing ultrafine fibrous membranes, which were then thermally treated at 150 degrees C to introduce chemical cross-linking between HMDI units and carbonyl groups of HPIM, resulting in HIVIDI-modified HPIM fibrous membranes (HMDI/HPIM-FMs). The solubility behavior has been altered by an introduced modification that makes membranes insoluble in all common organic solvents. Chemical cross-linking has been confirmed by using a Fourier transform infrared technique showing urethane linkage between HMDI and HPIM, and it was further supported by X-ray photoelectron microscopy and elemental analysis techniques that show a significant increase in the relative ratio of nitrogen in HMDI/HPIM-FMs compared to HPIM-FM. The average fiber diameters of fibrous membranes were found between 1.38 +/- 0.29 and 0.96 +/- 0.22 yin depending on the blend compositions and applied electrospinning parameters. Moreover, the water contact-angle value for HPIM-FM increased with the introduced HMDI modification from 140 +/- 4 degrees to 159 +/- 7 degrees, changing the nature of the membrane from hydrophobic to superhydrophobic. Consequently, HMDI/HPIM-FMs were successfully employed in oil/water separation due to the superhydrophobicity. In addition, the adsorption properties of HPIMFM and HMDI/HPIM-FMs were explored for common organic solvents. While both HPIM-FM and HMDI/HPIM-FMs show promising results, the structural stability of HMDI/HPIM-FMs in liquids was found to be more stable and reusable with respect to HPIM-FM. Hence, HMDI/HPIM-FMs are more favorable for organic adsorption and separation purposes from an aqueous system

Development of superhydrophobic electrospun fibrous membrane of polymers of intrinsic microporosity (PIM-2)

WOS: 000461001700011Polymers of intrinsic microporosity (PIMs) are increasingly recognized as a potential membrane material for adsorption and separation applications due to their permanent porosity and solution processability. PIM-2 can be produced using commercially available 5,5',6,6'-Tetrahydrozy-3,3,3',3'-tetramethyl-1,1'-spirobisindane and decafluorobiphenyl monomers in the powder form. It possesses considerable amount of fluorine in the polymer backbone and this feature could provide significant hydrophobicity to polymer. This research aims to investigate the fabrication of self-standing PIM-2 fibrous membranes by electrospinning method to introduce a useful material for adsorption applications. Electrospinning was performed using tetrachloroethane as a solvent and bead free, uniform fibers were produced as confirmed by SEM imaging. Average fiber diameter was calculated as 5.5 +/- 1.5 mu m for a self-standing fibrous membrane of PIM-2. Structural characterization was conducted using FT-IR, NMR and XPS spectroscopies showing the purity of pristine powder and fibrous membrane of PIM-2. Thermal stability of PIM-2 fibrous membrane was investigated using TGA and it shows no discernible weight loss below 450 degrees C. The porosity of fibrous membrane was investigated by N-2 adsorption/desorption measurements that indicates significant microporosity with similar to 600 m(2) g(-1) BET surface area. In addition, the hydrophobicity of PIM-2 was tested by water contact angle measurements, showing 155 +/- 6 degrees WCA, indicating super hydrophobicity owing to rough surface and high fluorine content. Consequently, the combination of straightforward synthesis, solution processability, high thermal stability, high surface area, and superhydrophobicity makes PIM-2 a promising candidate for adsorption applications. Therefore, it was successfully employed in organic and oil adsorption. Fibrous membranes of PIM-2 has shown up to 2200 +/- 100% and 1900 +/- 100% weight gain after in contact with silicon oil and DMSO respectively. In addition, dense membrane of PIM-2 was prepared by solvent casting method and the uptake ability was compared with fibrous membrane showing that fibrous form is more convenient for liquid adsorption applications

Removal of aniline from air and water by polymers of intrinsic microporosity (PIM-1) electrospun ultrafine fibers

WOS: 000427808900034PubMed ID: 29408119This research aims to investigate the possibility of electrospun fibers from Polymers of Intrinsic Microporosity (PIM-1) as an alternative adsorbent for aniline removal from both air and aqueous solution. Adsorption properties of electrospun PIM-1 fibers were compared with powder and film form of PIM-1. While electrospun PIM-1 nanofibrous mat can adsorb 871 mg g (1) aniline from air, it can also adsorb 78 +/- 5.4 mg g (1) aniline from aqueous environment when 50 mg L (1) aniline solution is used. The experimental maximum adsorption capacity of electrospun PIM-1 fibers was found as (q(e)) 138 mg g(-1). Langmuir and Freundlich isotherm models have been studied and Langmuir model found more appropriate for aniline adsorption on electrospun PIM-1 fibers. The study reveals that self-standing electrospun fibrous mat of PIM-1 has shown potential to be used as an efficient adsorbent material for the adsorption of VOCs from air and aqueous system thanks to its fast kinetic and high adsorption capacity. (C) 2018 Elsevier Inc. All rights reserved

Electrospinning of Ultrafine Poly(1-trimethylsilyl-1-propyne) [PTMSP] Fibers: Highly Porous Fibrous Membranes for Volatile Organic Compound Removal

WOS: 000476966800021Poly(1-trimethylsilyl-1-propyne) [PTMSP] possesses a rigid backbone chain with bulky trimethylsilyl side groups which limit the rotational freedom and provide packing-inefficiency that leads extremely high free volume. PTMSP is a hydrophobic polymer showing solubility in common organic solvents such as chloroform and tetrahydrofuran. Therefore, it can be formed as self-standing dense membrane (film). Hence, PTMSP is widely studied for separation applications owing to these outstanding properties. The aim of this research is to produce self-standing poly(1-trimethylsilyl-1-propyne) [PTMSP] fibrous membrane via electrospinning method to further enhance the application area of PTMSP. Electrospinning was achieved using tetrahydrofuran/tetrachloroethane (1:2 v/v) solvent mixture. Extensive optimization studies were performed to obtain bead-free and uniform ultrafine fibers which were obtained at 3.5% (w/v) polymer concentration with respect to solvent, and beads-on-string morphology was obtained below this concentration as confirmed by SEM imaging. Random and aligned fibers were produced using a stationary and a rotating collector, respectively. The optimized sample (P6), which was produced using 12 kV voltage and 20 cm tip-to-collector distance, possesses an average fiber diameter of 1.4 +/- 0.4 mu m. Additionally, PTMSP dense membrane was fabricated by solvent evaporation method to compare the properties with fibrous membrane. Structural characterization and elemental composition of PTMSP samples were conducted using FT-IR and H-1 NMR and XPS spectroscopies. Hydrophobicity of the samples was compared using their water contact angle measurements. While PTMSP dense membrane shows 90 +/- 2 degrees, the electrospun PTMSP fibrous membranes possess hydrophobic nature having 145 +/- 5 degrees and 152 +/- 2 degrees water contact angles for fibers having aligned and random morphology, respectively. In addition, fibrous membrane possesses high surface area that is the same as powder form showing similar to 850 m(2)/g BET surface area which is slightly higher than that of dense membrane (780 m(2)/g). Consequently, the high surface area electrospun PTMSP fibrous membrane was tested for volatile organic compounds (VOCs) removal as it can accommodate a significant amount of organic molecules in its porous structure. Furthermore, the VOC entrapment capacity of dense and fibrous membrane was compared using aniline, benzene, and toluene as model compounds. PTMSP membranes have shown the highest uptake for aniline where the uniform fiber morphology was maintained after sorption for fibrous membrane. In addition, lower boiling point VOCs, benzene and toluene, were trapped in fibrous membrane higher that the dense membrane since they cause swelling in fiber morphology

Amine modified electrospun PIM-1 ultrafine fibers for an efficient removal of methyl orange from an aqueous system

WOS: 000436940800026Polymers of Intrinsic Microporosity (PIM-1) is a promising material for adsorption and separation applications. While PIM-1 displays high affinity for neutral species, it shows lack of interaction with charged molecules in an aqueous system due to non-polar nature of it. Functionalization of PIM-1 provides an advantage of tailoring the interaction ability as well as the adsorption performance of PIM-1 towards target pollutants. In this study, electrospun Polymer of Intrinsic Microporosity (PIM-1) fibrous membrane (PIM-FM) was reacted with borane dimethyl sulfide complex to obtain amine modified PIM-1 fibrous membrane (AM-PIM-FM). Furthermore, PIM-1 film, which is referred as PIM-1 dense membrane (PIM-DM), was also modified under the same conditions as a control material. Structural analyses have confirmed that nitrile groups of PIM-1 have been fully converted to amine group as a result of the reduction reaction. Average fiber diameter of parent PIM-1 fibers was found 2.3 +/- 0.3 mu m, and it remained almost the same after the amine modification. In addition, no physical damage has been observed on fiber structure based on the SEM analysis. Both amine modified PIM-1 dense and fibrous membranes became insoluble in common organic solvents. Before the modification, water contact angle of PIM-FM was 138 +/- 2 degrees which also remained almost the same after the modification, showing water contact angle of 131 +/- 8 degrees. The insolubility along with amine functionality make membranes promising materials for adsorption of anionic dyes from wastewater. Here, dye (i.e. Methyl Orange) removal ability of AM-PIM-FM from an aqueous system was investigated and compared with parent PIM-1 (PIM-FM) as well as dense membrane form (AM-PIMDM). AM-PIM-FM shows extremely higher adsorption capacity than that of PIM-FM and AM-PIM-DM. The maximum adsorption capacity of AM-PIM-FM was found 312.5 mg g(-1) for Methyl Orange. Langmuir isotherm model was found more favorable for the adsorption. AM-PIM-FM was employed effectively in continuous adsorption/desorption studies for several times without having any damage on fiber morphology using batch adsorption process. Furthermore, AM-PIM-FM was successfully used as a molecular filter for the removal of methyl orange from an aqueous system. The results indicate that AM-PIM-FM could be a promising adsorbent for removal of anionic molecules from an aqueous system

Electrospinning of uniform nanofibers of Polymers of Intrinsic Microporosity (PIM-1): The influence of solution conductivity and relative humidity

WOS: 000483922700023Polymers of Intrinsic Microporosity (PIMs) are ultra-permeable macromolecules, which can be cast as a dense membrane and exploited in a wide spectrum of applications, particularly for gas separation owing to their extremely large inner surface area, free volume and high gas permeability. While they are mostly intended to serve as membranes for gas separation, in recent years, they have been also employed in water treatment applications owing to their solution processability, which enables the production of fibrous membranes by electrospinning. The fibrous form provides an increase in sorption performance, water permeability and flux for their application in water treatment. However, owing to the low conductivity of PIM-1 solutions in 1,1,2,2-tetrachloroethane (TeCA) that is the ideal solvent for the electrospinning of PIM-1 solutions, a higher polymer concentration is required to produce bead-free fibers. Furthermore, the electrospinning of highly concentrated PIM-1 solutions leads to the formation of microfibers. To tackle these problems, we herein incorporated an ammonium salt (i.e., tetraethylammonium bromide, TEAB) to increase the conductivity of PIM-1 solutions and study the impact of solution conductivity on the electrospinning of PIM-1 solutions. In parallel to the conductivity study, the influence of relative humidity on the electrospinning and morphology of PIM-1 fibers was explored. The addition of TEAB significantly increased the solution conductivity and drastically enhanced the electrospinnability of PIM-1. The electrospinning of PIM-1 solutions (10% (w/v)) in the presence 7.5 wt% TEAB (with respect to PIM-1) led to bead-free fibers, while at the same concentration, electrosprayed beads and droplet splashing were observed in the absence of TEAB. On the other hand, increasing humidity did not influence the electrospinnability of PIM-1 and the fiber texture, however, less fibers were formed in a given time at very high humidity conditions (similar to 80%). Overall, the experimental findings revealed that the addition of the salt drastically enhanced the electrospinnability of PIM-1 solutions owing to the enhanced conductivity and could lead to the formation of very thin PIM-1 fibers with 160 nm in diameter while no significant effect of relative humidity on the electrospinnability of PIM-1 solutions was observed

Selective dye adsorption by chemically-modified and thermally-treated polymers of intrinsic microporosity

WOS: 000395228500010PubMed ID: 28068548Nitrile groups in the polymer of intrinsic microporosity PIM-1 were modified by base-catalysed hydrolysis, by reaction with ethanolamine and diethanolamine, and by reduction to amine, and the products investigated for their ability to take up a range of dyes from aqueous or ethanolic solution. Hydrolysed products exhibited selectivity for cationic over anionic species, while other products showed the reverse selectivity. At low pH, amine-PIM-1 adsorbed more than its own weight of the anionic dyes Orange II and Acid Red I from aqueous solution. It was demonstrated that adsorbed Orange II can be removed with basic ethanol. Mixtures of oppositely charged dyes undergo precipitation, but selective adsorption of one dye leads to dissolution of the other from the precipitate. Thermal treatment of the chemically modified polymers at 300 degrees C for 48 h in an inert atmosphere led to structural changes that reduced the dye adsorption capacity. On the basis of a combination of thermogravimetric and elemental analysis with ATR-IR and NMR spectroscopy, feasible structures are suggested for the thermally-treated polymers. (C) 2017 The Authors. Published by Elsevier Inc.Republic of Turkey Ministry of National EducationMinistry of National Education - Turkey; United Kingdom EPSRCEngineering & Physical Sciences Research Council (EPSRC) [EP/M001342/1, EP/M01486X/1]; Engineering and Physical Sciences Research CouncilEngineering & Physical Sciences Research Council (EPSRC) [EP/M01486X/1]Bekir Satilmis is funded by the Republic of Turkey Ministry of National Education. Our research is supported by United Kingdom EPSRC grants EP/M001342/1 and EP/M01486X/1

Base-catalysed hydrolysis of PIM-1: amide versus carboxylate formation

Controlled hydrolysis of PIM-1 yields polymers tailored for the selective adsorption of ionic dyes.</p

Hydroxyalkylaminoalkylamide PIMs: Selective adsorption by ethanolamine- and diethanolamine-modified PIM-1

The polymer of intrinsic microporosity PIM-1 was modified by reaction with ethanolamine and with diethanolamine, and the modified polymers characterized by infrared spectroscopy, solid-state NMR spectroscopy, elemental analysis, thermogravimetric analysis and nitrogen adsorption. Various possible reaction products were considered, and the results indicated that hydroxyalkylaminoalkylamide structures were obtained. Gas adsorption measurements showed that ethanolamine modification increased the ideal CO₂/N₂ selectivity. Studies of dye adsorption from aqueous solution demonstrated that the reaction products showed strong selectivity for the anionic dye Orange II, compared to the cationic dye Safranin O. Mass uptakes of the anionic dye by ethanolamine-modified PIM-1 samples were up to 2 orders of magnitude higher than for the parent polymer