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Polymers
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Polymeric Membranes
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Polymeric Membranes

A special issue of Polymers (ISSN 2073-4360).

Deadline for manuscript submissions: closed (15 November 2017) | Viewed by 121441

Special Issue Editor

Prof. Dr. Ying-Ling Liu

E-Mail Website
Guest Editor
Department of Chemical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
Interests: polymer chemistry; thermosets; functional polymers; membranes; pervaporation; proton exchange membranes; nanocomposites; self-healing polymers; surface functionalization

Special Issue Information

Dear Colleagues,

Polymeric membranes exhibit the functions of selective material transportation/permeation. Their structures can be both dense and porous, thin-film composites and self-standing, single component and mixed-matrixes. In addition to their functions, the properties of membrane are also of concern in practical processes and long-term operations. Studies on the structural design, membrane preparation, modulus assembly, and process design, as well as integration of topics are of high interest. Polymeric membranes are an attractive and potential topic for researchers in the fields of polymer chemistry, physics, engineering, and applications.

This Special Issue aims to collect research on polymeric membranes on various topics and scopes, to demonstrate the recent progress in polymeric membranes, and to provide a communication platform for the researchers in the related fields.

Prof. Dr. Ying-Ling Liu
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • polymeric membrane
  • membrane formation
  • filtration
  • pervaporation
  • gas separation
  • oil-water separation
  • proton exchange membrane
  • fouling

Published Papers (17 papers)

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Research

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13 pages, 2927 KiB  
Article
Synthesis and Crosslinking of Polyether-Based Main Chain Benzoxazine Polymers and Their Gas Separation Performance
by Muntazim Munir Khan, Karabi Halder, Sergey Shishatskiy and Volkan Filiz
Polymers 2018, 10(2), 221; https://doi.org/10.3390/polym10020221 - 23 Feb 2018
Cited by 33 | Viewed by 10329
Abstract
The poly(ethylene glycol)-based benzoxazine polymers were synthesized via a polycondensation reaction between Bisphenol-A, paraformaldehyde, and poly(ether diamine)/(Jeffamine®). The structures of the polymers were confirmed by proton nuclear magnetic resonance spectroscopy (1H-NMR), indicating the presence of a cyclic benzoxazine ring. [...] Read more.
The poly(ethylene glycol)-based benzoxazine polymers were synthesized via a polycondensation reaction between Bisphenol-A, paraformaldehyde, and poly(ether diamine)/(Jeffamine®). The structures of the polymers were confirmed by proton nuclear magnetic resonance spectroscopy (1H-NMR), indicating the presence of a cyclic benzoxazine ring. The polymer solutions were casted on the glass plate and cross-linked via thermal treatment to produce tough and flexible films without using any external additives. Thermal properties and the crosslinking behaviour of these polymers were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Single gas (H2, O2, N2, CO2, and CH4) transport properties of the crosslinked polymeric membranes were measured by the time-lag method. The crosslinked PEG-based polybenzoxazine membranes show improved selectivities for CO2/N2 and CO2/CH4 gas pairs. The good separation selectivities of these PEG-based polybenzoxazine materials suggest their utility as efficient thin film composite membranes for gas and liquid membrane separation technology. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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16 pages, 3848 KiB  
Article
Thermal Stability and Water Content Study of Void-Free Electrospun SPEEK/Cloisite Membrane for Direct Methanol Fuel Cell Application
by Nuha Awang, Juhana Jaafar and Ahmad Fauzi Ismail
Polymers 2018, 10(2), 194; https://doi.org/10.3390/polym10020194 - 15 Feb 2018
Cited by 30 | Viewed by 4194
Abstract
Void-free electrospun SPEEK/Cloisite15A® densed (SP/e-spunCL) membranes are prepared. Different loadings of Cloisite15A® (0.10, 0.15, 0.20, 0.25 and 0.30 wt %) are incorporated into electrospun fibers. The physico-chemical characteristics (methanol permeability, water uptake and proton conductivity) of the membranes are observed. Thermal [...] Read more.
Void-free electrospun SPEEK/Cloisite15A® densed (SP/e-spunCL) membranes are prepared. Different loadings of Cloisite15A® (0.10, 0.15, 0.20, 0.25 and 0.30 wt %) are incorporated into electrospun fibers. The physico-chemical characteristics (methanol permeability, water uptake and proton conductivity) of the membranes are observed. Thermal stability of all membranes is observed using Thermal Gravimetry Analysis (TGA). The thrree stages of degradation range between 163.1 and 613.1 °C. Differential Scanning Calorimetry (DSC) is used to study the wettability of the membranes. SP/e-spunCL15 shows the lowest freezing bound water of 15.27%, which contributed to the lowest methanol permeability. The non-freezing bound water that proportionally increased with proton conductivity of SP/e-spunCL15 membrane is the highest, 10.60%. It is suggested that the electrospinning as the fabricating method has successfully exfoliated the Cloisite in the membrane surface structure, contributing to the decrease of methanol permeability, while the retained water has led to the enhancement of proton conductivity. This new fabrication method of SP/e-spunCL membrane is said to be a desirable polymer electrolyte membrane for future application in direct methanol fuel cell field. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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14 pages, 2260 KiB  
Article
The Influence of the Morphology and Mechanical Properties of Polymer Inclusion Membranes (PIMs) on Zinc Ion Separation from Aqueous Solutions
by Katarzyna Witt, Elzbieta Radzyminska-Lenarcik, Artur Kosciuszko, Magdalena Gierszewska and Kamil Ziuziakowski
Polymers 2018, 10(2), 134; https://doi.org/10.3390/polym10020134 - 30 Jan 2018
Cited by 26 | Viewed by 4264
Abstract
The transport of Zn(II) ions across polymer inclusion membranes (PIMs) with acetylacetone (ACAC) or di(2-ethylhexyl)phosphoric acid (D2EHPA) as carriers was studied. Polymeric membranes consisting of polyvinylchloride (PVC) as the support, bis(2-ethylhexyl)adipate (DAO) as plasticizer, and ACAC or D2EHPA [...] Read more.
The transport of Zn(II) ions across polymer inclusion membranes (PIMs) with acetylacetone (ACAC) or di(2-ethylhexyl)phosphoric acid (D2EHPA) as carriers was studied. Polymeric membranes consisting of polyvinylchloride (PVC) as the support, bis(2-ethylhexyl)adipate (DAO) as plasticizer, and ACAC or D2EHPA as ion carriers were investigated. The highest recovery factors for Zn(II) ions were observed in the case of a membrane containing 20% acac (99.6%) and 60% D2EHPA (56.3%). The prepared PIMs were examined using atomic force microscopy (AFM) techniques. Their mechanical properties were also determined. The influence of membrane morphology and mechanical properties on the zinc transport process was discussed. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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11 pages, 1940 KiB  
Article
Preparation, Characterization, and Performance Evaluation of Polysulfone Hollow Fiber Membrane with PEBAX or PDMS Coating for Oxygen Enhancement Process
by Kok Chung Chong, Soon Onn Lai, Woei Jye Lau, Hui San Thiam, Ahmad Fauzi Ismail and Rosyiela Azwa Roslan
Polymers 2018, 10(2), 126; https://doi.org/10.3390/polym10020126 - 28 Jan 2018
Cited by 34 | Viewed by 5807
Abstract
Air pollution is a widely discussed topic amongst the academic and industrial spheres as it can bring adverse effects to human health and economic loss. As humans spend most of their time at the office and at home, good indoor air quality with [...] Read more.
Air pollution is a widely discussed topic amongst the academic and industrial spheres as it can bring adverse effects to human health and economic loss. As humans spend most of their time at the office and at home, good indoor air quality with enriched oxygen concentration is particularly important. In this study, polysulfone (PSF) hollow fiber membranes fabricated by dry-jet wet phase inversion method were coated by a layer of polydimethylsiloxane (PDMS) or poly(ether block amide) (PEBAX) at different concentrations and used to evaluate their performance in gas separation for oxygen enrichment. The surface-coated membranes were characterized using SEM and EDX to determine the coating layer thickness and surface chemical properties, respectively. Results from the gas permeation study revealed that the PSF membrane coated with PDMS offered higher permeance and selectivity compared to the membrane coated with PEBAX. The best performing PDMS-coated membrane demonstrated oxygen and nitrogen gas permeance of 18.31 and 4.01 GPU, respectively with oxygen/nitrogen selectivity of 4.56. Meanwhile, the PEBAX-coated membrane only showed 12.23 and 3.11 GPU for oxygen and nitrogen gas, respectively with a selectivity of 3.94. It can be concluded the PDMS coating is more promising for PSF hollow fiber membrane compared to the PEBAX coating for the oxygen enrichment process. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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17 pages, 3663 KiB  
Article
Highly Zeolite-Loaded Polyvinyl Alcohol Composite Membranes for Alkaline Fuel-Cell Electrolytes
by Po-Ya Hsu, Ting-Yu Hu, Selvaraj Rajesh Kumar, Chia-Hao Chang, Kevin C.-W. Wu, Kuo-Lun Tung and Shingjiang Jessie Lue
Polymers 2018, 10(1), 102; https://doi.org/10.3390/polym10010102 - 22 Jan 2018
Cited by 34 | Viewed by 8141
Abstract
Having a secure and stable energy supply is a top priority for the global community. Fuel-cell technology is recognized as a promising electrical energy generation system for the twenty-first century. Polyvinyl alcohol/zeolitic imidazolate framework-8 (PVA/ZIF-8) composite membranes were successfully prepared in this work [...] Read more.
Having a secure and stable energy supply is a top priority for the global community. Fuel-cell technology is recognized as a promising electrical energy generation system for the twenty-first century. Polyvinyl alcohol/zeolitic imidazolate framework-8 (PVA/ZIF-8) composite membranes were successfully prepared in this work from direct ZIF-8 suspension solution (0–45.4 wt %) and PVA mixing to prevent filler aggregation for direct methanol alkaline fuel cells (DMAFCs). The ZIF-8 fillers were chosen for the appropriate cavity size as a screening aid to allow water and suppress methanol transport. Increased ionic conductivities and suppressed methanol permeabilities were achieved for the PVA/40.5% ZIF-8 composites, compared to other samples. A high power density of 173.2 mW cm−2 was achieved using a KOH-doped PVA/40.5% ZIF-8 membrane in a DMAFC at 60 °C with 1–2 mg cm−2 catalyst loads. As the filler content was raised beyond 45.4 wt %, adverse effects resulted and the DMAFC performance (144.9 mW cm−2) was not improved further. Therefore, the optimal ZIF-8 content was approximately 40.5 wt % in the polymeric matrix. The specific power output was higher (58 mW mg−1) than most membranes reported in the literature (3–18 mW mg−1). Full article
(This article belongs to the Special Issue Polymeric Membranes)
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21 pages, 4803 KiB  
Article
Development and Characterization of Defect-Free Matrimid® Mixed-Matrix Membranes Containing Activated Carbon Particles for Gas Separation
by Fynn Weigelt, Prokopios Georgopanos, Sergey Shishatskiy, Volkan Filiz, Torsten Brinkmann and Volker Abetz
Polymers 2018, 10(1), 51; https://doi.org/10.3390/polym10010051 - 08 Jan 2018
Cited by 49 | Viewed by 8212
Abstract
In this work, mixed-matrix membranes (MMMs) for gas separation in the form of thick films were prepared via the combination of the polymer Matrimid® 5218 and activated carbons (AC). The AC particles had a mean particle size of 1.5 μm and a [...] Read more.
In this work, mixed-matrix membranes (MMMs) for gas separation in the form of thick films were prepared via the combination of the polymer Matrimid® 5218 and activated carbons (AC). The AC particles had a mean particle size of 1.5 μm and a mean pore diameter of 1.9 nm. The films were prepared by slow solvent evaporation from casting solutions in chloroform, which had a varying polymer–AC ratio. It was possible to produce stable films with up to a content of 50 vol % of AC. Thorough characterization experiments were accomplished via differential scanning calorimetry and thermogravimetric analysis, while the morphology of the MMMs was also investigated via scanning electron microscopy. The gas transport properties were revealed by employing time-lag measurements for different pure gases as well as sorption balance experiments for the filler particles. It was found that defect free Matrimid® MMMs with AC were prepared and the increase of the filler content led to a higher effective permeability for different gases. The single gas selectivity αij of different gas pairs maintained stable values with the increase of AC content, regardless of the steep increase in the effective permeability of the pure gases. Estimation of the solubilities and the diffusivities of the Matrimid®, AC, and MMMs allowed for the explanation of the increasing permeabilities of the MMMs, with the increase of AC content by modelling. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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10953 KiB  
Article
Polypropylene-Based Porous Membranes: Influence of Polymer Composition, Extrusion Draw Ratio and Uniaxial Strain
by Pilar Castejón, Kian Habibi, Amir Saffar, Abdellah Ajji, Antonio B. Martínez and David Arencón
Polymers 2018, 10(1), 33; https://doi.org/10.3390/polym10010033 - 29 Dec 2017
Cited by 22 | Viewed by 7610
Abstract
Several commercial grades of homo-polymer and its blends were selected to prepare microporous membranes through melt extrusion-annealing-uniaxial stretching technique (MEAUS). Branched or very fluid polypropylene was employed to modify the polymeric composition. In some blends, micro-sized calcium carbonate was added. We analysed the [...] Read more.
Several commercial grades of homo-polymer and its blends were selected to prepare microporous membranes through melt extrusion-annealing-uniaxial stretching technique (MEAUS). Branched or very fluid polypropylene was employed to modify the polymeric composition. In some blends, micro-sized calcium carbonate was added. We analysed the influence of sample composition, extrusion draw ratio, and we performed a deep study concerning the uniaxial strain rate, using in some cases extreme strain rates and strain extents. The crystalline features were studied by Differential Scanning Calorimetry (DSC), and the morphology of porous structure was analyzed through Scanning Electron Microscopy (SEM). Thermal stability and thermomechanical performance was measured by thermogravimetric analysis (TGA) and dynamic-mechanical-thermal (DTMA) study. A close relationship was found between crystalline characteristics, porous morphology and the trends registered for permeability. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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5446 KiB  
Article
Preparation and Characterization of Novel Polyvinylidene Fluoride/2-Aminobenzothiazole Modified Ultrafiltration Membrane for the Removal of Cr(VI) in Wastewater
by Xiuju Wang, Kaili Zhou, Zhun Ma, Xingjie Lu, Liguo Wang, Zhongpeng Wang and Xueli Gao
Polymers 2018, 10(1), 19; https://doi.org/10.3390/polym10010019 - 25 Dec 2017
Cited by 20 | Viewed by 4408
Abstract
Hexavalent chromium is one of the main heavy metal pollutants. As the environmental legislation becomes increasingly strict, seeking new technology to treat wastewater containing hexavalent chromium is becoming more and more important. In this research, a novel modified ultrafiltration membrane that could be [...] Read more.
Hexavalent chromium is one of the main heavy metal pollutants. As the environmental legislation becomes increasingly strict, seeking new technology to treat wastewater containing hexavalent chromium is becoming more and more important. In this research, a novel modified ultrafiltration membrane that could be applied to adsorb and purify water containing hexavalent chromium, was prepared by polyvinylidene fluoride (PVDF) blending with 2-aminobenzothiazole via phase inversion. The membrane performance was characterized by evaluation of the instrument of membrane performance, infrared spectroscopy (FTIR), scanning electron microscope (SEM), and water contact angle measurements. The results showed that the pure water flux of the PVDF/2-aminobenzothiazole modified ultrafiltration membrane was 231.27 L/m2·h, the contact angle was 76.1°, and the adsorption capacity of chromium ion was 157.75 µg/cm2. The PVDF/2-aminobenzothiazole modified ultrafiltration membrane presented better adsorption abilities for chromium ion than that of the traditional PVDF membrane. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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3627 KiB  
Article
New Development of Membrane Base Optoelectronic Devices
by Leon Hamui, María Elena Sánchez-Vergara, Rocío Sánchez-Ruiz, Diego Ruanova-Ferreiro, Ricardo Ballinas Indili and Cecilio Álvarez-Toledano
Polymers 2018, 10(1), 16; https://doi.org/10.3390/polym10010016 - 23 Dec 2017
Cited by 9 | Viewed by 4821
Abstract
It is known that one factor that affects the operation of optoelectronic devices is the effective protection of the semiconductor materials against environmental conditions. The permeation of atmospheric oxygen and water molecules into the device structure induces degradation of the electrodes and the [...] Read more.
It is known that one factor that affects the operation of optoelectronic devices is the effective protection of the semiconductor materials against environmental conditions. The permeation of atmospheric oxygen and water molecules into the device structure induces degradation of the electrodes and the semiconductor. As a result, in this communication we report the fabrication of semiconductor membranes consisting of Magnesium Phthalocyanine-allene (MgPc-allene) particles dispersed in Nylon 11 films. These membranes combine polymer properties with organic semiconductors properties and also provide a barrier effect for the atmospheric gas molecules. They were prepared by high vacuum evaporation and followed by thermal relaxation technique. For the characterization of the obtained membranes, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) were used to determine the chemical and microstructural properties. UV-ViS, null ellipsometry, and visible photoluminescence (PL) at room temperature were used to characterize the optoelectronic properties. These results were compared with those obtained for the organic semiconductors: MgPc-allene thin films. Additionally, semiconductor membranes devices have been prepared, and a study of the device electronic transport properties was conducted by measuring electrical current density-voltage (J-V) characteristics by four point probes with different wavelengths. The resistance properties against different environmental molecules are enhanced, maintaining their semiconductor functionality that makes them candidates for optoelectronic applications. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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5298 KiB  
Article
PVDF Membrane Morphology—Influence of Polymer Molecular Weight and Preparation Temperature
by Monika Haponska, Anna Trojanowska, Adrianna Nogalska, Renata Jastrzab, Tania Gumi and Bartosz Tylkowski
Polymers 2017, 9(12), 718; https://doi.org/10.3390/polym9120718 - 15 Dec 2017
Cited by 51 | Viewed by 13159
Abstract
In this study, we successfully prepared nine non-woven, supported polyvinylidene fluoride (PVDF) membranes, using a phase inversion precipitation method, starting from a 15 wt % PVDF solution in N-methyl-2-pyrrolidone. Various membrane morphologies were obtained by using (1) PVDF polymers, with diverse molecular [...] Read more.
In this study, we successfully prepared nine non-woven, supported polyvinylidene fluoride (PVDF) membranes, using a phase inversion precipitation method, starting from a 15 wt % PVDF solution in N-methyl-2-pyrrolidone. Various membrane morphologies were obtained by using (1) PVDF polymers, with diverse molecular weights ranging from 300 to 700 kDa, and (2) different temperature coagulation baths (20, 40, and 60 ± 2 °C) used for the film precipitation. An environmental scanning electron microscope (ESEM) was used for surface and cross-section morphology characterization. An atomic force microscope (AFM) was employed to investigate surface roughness, while a contact angle (CA) instrument was used for membrane hydrophobicity studies. Fourier transform infrared spectroscopy (FTIR) results show that the fabricated membranes are formed by a mixture of TGTG’ chains, in α phase crystalline domains, and all-TTTT trans planar zigzag chains characteristic to β phase. Moreover, generated results indicate that the phases’ content and membrane morphologies depend on the polymer molecular weight and conditions used for the membranes’ preparation. The diversity of fabricated membranes could be applied by the End User Industries for different applications. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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3391 KiB  
Article
Proton Conductive Channel Optimization in Methanol Resistive Hybrid Hyperbranched Polyamide Proton Exchange Membrane
by Liying Ma, Jing Li, Jie Xiong, Guoxiao Xu, Zhao Liu and Weiwei Cai
Polymers 2017, 9(12), 703; https://doi.org/10.3390/polym9120703 - 14 Dec 2017
Cited by 7 | Viewed by 5019
Abstract
Based on a previously developed polyamide proton conductive macromolecule, the nano-scale structure of the self-assembled proton conductive channels (PCCs) is adjusted via enlarging the nano-scale pore size within the macromolecules. Hyperbranched polyamide macromolecules with different size are synthesized from different monomers to tune [...] Read more.
Based on a previously developed polyamide proton conductive macromolecule, the nano-scale structure of the self-assembled proton conductive channels (PCCs) is adjusted via enlarging the nano-scale pore size within the macromolecules. Hyperbranched polyamide macromolecules with different size are synthesized from different monomers to tune the nano-scale pore size within the macromolecules, and a series of hybrid membranes are prepared from these two micromoles to optimize the PCC structure in the proton exchange membrane. The optimized membrane exhibits methanol permeability low to 2.2 × 10−7 cm2/s, while the proton conductivity of the hybrid membrane can reach 0.25 S/cm at 80 °C, which was much higher than the value of the Nafion 117 membrane (0.192 S/cm). By considering the mechanical, dimensional, and the thermal properties, the hybrid hyperbranched polyamide proton exchange membrane (PEM) exhibits promising application potential in direct methanol fuel cells (DMFC). Full article
(This article belongs to the Special Issue Polymeric Membranes)
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3675 KiB  
Article
Poly(piperazine-amide)/PES Composite Multi-Channel Capillary Membranes for Low-Pressure Nanofiltration
by Jan O. Back, Martin Spruck, Marc Koch, Lukas Mayr, Simon Penner and Marco Rupprich
Polymers 2017, 9(12), 654; https://doi.org/10.3390/polym9120654 - 28 Nov 2017
Cited by 7 | Viewed by 6380
Abstract
The mechanical stability of conventional single-channel capillary fibres can be improved in a multi-channel geometry, which has previously found application in ultrafiltration. In this work, multi-channel polyethersulfone (PES) capillary membranes comprising seven feed channels were successfully fabricated in an enhanced steam–dry–wet spinning process [...] Read more.
The mechanical stability of conventional single-channel capillary fibres can be improved in a multi-channel geometry, which has previously found application in ultrafiltration. In this work, multi-channel polyethersulfone (PES) capillary membranes comprising seven feed channels were successfully fabricated in an enhanced steam–dry–wet spinning process and coated on the inner surface with a thin polyamide (PA) layer via interfacial polymerization (IP). The coating procedure consisted of impregnating the support multi-channel capillary membranes (MCM) with an aqueous piperazine solution, flushing with nitrogen gas to remove excess droplets, and pumping an organic trimesoylchloride solution through the channels. Insights into the interfacial polymerization process were gained through the investigation of various parameters, including monomer ratio, contact time, and drying time. Membranes were characterised via scanning electron microscopy (SEM), atomic force microscopy (AFM), and filtration experiments. The optimisation of both the PES support membrane and IP process parameters allowed for the fabrication of composite MCM with an MgSO4 rejection of 91.4% and a solute flux of 68.8 L m−2 h−1 at an applied pressure of 3 bar. The fabricated composite MCM demonstrates that a favourable multi-channel arrangement can be upgraded with a PA layer for application in low-pressure nanofiltration. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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3136 KiB  
Article
Silane Cross-Linked Sulfonted Poly(Ether Ketone/Ether Benzimidazole)s for Fuel Cell Applications
by Zilu Yao, Mengbing Cui, Zhenghui Zhang, Liang Wu and Tongwen Xu
Polymers 2017, 9(12), 631; https://doi.org/10.3390/polym9120631 - 23 Nov 2017
Cited by 16 | Viewed by 6386
Abstract
γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH-560) was incorporated in various proportions into side-chain-type sulfonated poly(ether ketone/ether benzimidazole) (SPEKEBI) as a crosslinker, to make membranes with high ion exchange capacities and excellent performance for direct methanol fuel cells (DMFCs). Systematical measurements including Fourier transform infrared (FT-IR), scanning [...] Read more.
γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH-560) was incorporated in various proportions into side-chain-type sulfonated poly(ether ketone/ether benzimidazole) (SPEKEBI) as a crosslinker, to make membranes with high ion exchange capacities and excellent performance for direct methanol fuel cells (DMFCs). Systematical measurements including Fourier transform infrared (FT-IR), scanning electron microscopy-energy-dispersive and X-ray photoelectron spectroscopy (XPS) proved the complete disappearance of epoxy groups in KH-560 and the existence of Si in the membranes. The resulting membranes showed increased mechanical strength and thermal stability compared to the unmodified sulfonated poly(ether ketone/ether benzimidazole) membrane in appropriate doping amount. Meanwhile, the methanol permeability has decreased, leading to the increase of relative selectivities of SPEKEBI-x-SiO2 membranes. Furthermore, the H2/O2 cell performance of SPEKEBI-2.5-SiO2 membrane showed a much higher peak power density compared with the pure SPEKEBI memrbrane. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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5078 KiB  
Article
Effect of PVA Blending on Structural and Ion Transport Properties of CS:AgNt-Based Polymer Electrolyte Membrane
by Shujahadeen B. Aziz, Omed Gh. Abdullah, Sarkawt A. Hussein and Hameed M. Ahmed
Polymers 2017, 9(11), 622; https://doi.org/10.3390/polym9110622 - 15 Nov 2017
Cited by 72 | Viewed by 8086
Abstract
In this work, the role of poly(vinyl alcohol) (PVA) blending on structural and electrical properties of chitosan:silver nitrate systems is studied. The X-ray diffraction (XRD) results show that the crystalline phase of chitosan (CS) is greatly scarified by silver nitrate (AgNt) salt. The [...] Read more.
In this work, the role of poly(vinyl alcohol) (PVA) blending on structural and electrical properties of chitosan:silver nitrate systems is studied. The X-ray diffraction (XRD) results show that the crystalline phase of chitosan (CS) is greatly scarified by silver nitrate (AgNt) salt. The crystalline domain of CS:AgNt is more broadened at 10 wt % of PVA. The spike and semicircular arcs can be separated in impedance plots. At high temperatures, the spike regions remained. The direct current (DC) conductivity was calculated from the bulk resistance obtained from the impedance plots. The dielectric constant and DC conductivity versus PVA content exhibited similar behavior. The maximum DC conductivity at ambient temperature was 1.1 × 10−6 S/cm for 10 wt % of PVA. The DC ionic conductivity increased to 9.95 × 10−5 S/cm at 80 °C. Above 10 wt % of PVA, the drop in DC conductivity and dielectric constant were observed due to the increase in viscosity. Shifting of relaxation peaks towards the lower frequency revealed the increase of resistivity of the samples. The linear increase of DC conductivity versus 1000/T indicated that ion transport followed the Arrhenius model. The incomplete semicircular arc in Argand plots indicated the non-Debye type of relaxation process. The Argand plots were used to distinguish between conductivity relaxation and viscoelastic relaxation. Three regions were distinguished in the alternating current (AC) spectra of the blend electrolyte samples. The plateau region in AC spectra was used to estimate the DC conductivity. The estimated DC conductivity from the AC spectra was close to those calculated from the impedance plots. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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10276 KiB  
Article
Correlating PSf Support Physicochemical Properties with the Formation of Piperazine-Based Polyamide and Evaluating the Resultant Nanofiltration Membrane Performance
by Micah Belle Marie Yap Ang, Victor Jr. Lau, Yan-Li Ji, Shu-Hsien Huang, Quan-Fu An, Alvin R. Caparanga, Hui-An Tsai, Wei-Song Hung, Chien-Chieh Hu, Kueir-Rarn Lee and Juin-Yih Lai
Polymers 2017, 9(10), 505; https://doi.org/10.3390/polym9100505 - 13 Oct 2017
Cited by 40 | Viewed by 6939
Abstract
Membrane support properties influence the performance of thin-film composite nanofiltration membranes. We fabricated several polysulfone (PSf) supports. The physicochemical properties of PSf were altered by adding polyethylene glycol (PEG) of varying molecular weights (200–35,000 g/mol). This alteration facilitated the formation of a thin [...] Read more.
Membrane support properties influence the performance of thin-film composite nanofiltration membranes. We fabricated several polysulfone (PSf) supports. The physicochemical properties of PSf were altered by adding polyethylene glycol (PEG) of varying molecular weights (200–35,000 g/mol). This alteration facilitated the formation of a thin polyamide layer on the PSf surface during the interfacial polymerization reaction involving an aqueous solution of piperazine containing 4-aminobenzoic acid and an organic solution of trimesoyl chloride. Attenuated total reflectance-Fourier transform infrared validated the presence of PEG in the membrane support. Scanning electron microscopy and atomic force microscopy illustrated that the thin-film polyamide layer morphology transformed from a rough to a smooth surface. A cross-flow filtration test indicated that a thin-film composite polyamide membrane comprising a PSf support (TFC-PEG20k) with a low surface porosity, small pore size, and suitable hydrophilicity delivered the highest water flux and separation efficiency (J = 81.1 ± 6.4 L·m−2·h−1, RNa2SO4 = 91.1% ± 1.8%, and RNaCl = 35.7% ± 3.1% at 0.60 MPa). This membrane had a molecular weight cutoff of 292 g/mol and also a high rejection for negatively charged dyes. Therefore, a PSf support exhibiting suitable physicochemical properties endowed a thin-film composite polyamide membrane with high performance. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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Article
A New Polymer-Based Fluorescent Chemosensor Incorporating Propane-1,3-Dione and 2,5-Diethynylbenzene Moieties for Detection of Copper(II) and Iron(III)
by Dongliang Yang, Chunhui Dai, Yanling Hu, Shuli Liu, Lixing Weng, Zhimin Luo, Yixiang Cheng and Lianhui Wang
Polymers 2017, 9(7), 267; https://doi.org/10.3390/polym9070267 - 06 Jul 2017
Cited by 25 | Viewed by 5889
Abstract
A novel conjugated polymer (PDBDBM) was developed by the polymerization of 1,4-dioctyloxy-2,5-diethynylbenzene with 1,3-bis(4-bromophenyl)propane-1,3-dione based on Pd-catalyzed Sonogashira-coupling reaction. The obtained polymer PDBDBM exhibited bright green photoluminescence under UV irradiation. According to the metal ion titration experiments, PDBDBM showed high sensitivity and selectivity [...] Read more.
A novel conjugated polymer (PDBDBM) was developed by the polymerization of 1,4-dioctyloxy-2,5-diethynylbenzene with 1,3-bis(4-bromophenyl)propane-1,3-dione based on Pd-catalyzed Sonogashira-coupling reaction. The obtained polymer PDBDBM exhibited bright green photoluminescence under UV irradiation. According to the metal ion titration experiments, PDBDBM showed high sensitivity and selectivity for detection of Cu2+ and Fe3+ over other metal ions. The fluorescent detection limits of PDBDBM were calculated to be 5 nM for Cu2+ and 0.4 μM for Fe3+ and the Stern–Volmer quenching constant for Cu2+ and Fe3+ were found to be 1.28 × 108 M−1 and 2.40 × 104 M−1, respectively. These results indicated that the polymer can be used as a potential probe for Cu2+ and Fe3+ detection. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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Review

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Review
Recent Advances in the Fabrication of Membranes Containing “Ion Pairs” for Nanofiltration Processes
by Yan-Li Ji, Bing-Xin Gu, Quan-Fu An and Cong-Jie Gao
Polymers 2017, 9(12), 715; https://doi.org/10.3390/polym9120715 - 14 Dec 2017
Cited by 40 | Viewed by 9583
Abstract
In the face of serious environmental pollution and water scarcity problems, the membrane separation technique, especially high efficiency, low energy consumption, and environmental friendly nanofiltration, has been quickly developed. Separation membranes with high permeability, good selectivity, and strong antifouling properties are critical for [...] Read more.
In the face of serious environmental pollution and water scarcity problems, the membrane separation technique, especially high efficiency, low energy consumption, and environmental friendly nanofiltration, has been quickly developed. Separation membranes with high permeability, good selectivity, and strong antifouling properties are critical for water treatment and green chemical processing. In recent years, researchers have paid more and more attention to the development of high performance nanofiltration membranes containing “ion pairs”. In this review, the effects of “ion pairs” characteristics, such as the super-hydrophilicity, controllable charge character, and antifouling property, on nanofiltration performances are discussed. A systematic survey was carried out on the various approaches and multiple regulation factors in the fabrication of polyelectrolyte complex membranes, zwitterionic membranes, and charged mosaic membranes, respectively. The mass transport behavior and antifouling mechanism of the membranes with “ion pairs” are also discussed. Finally, we present a brief perspective on the future development of advanced nanofiltration membranes with “ion pairs”. Full article
(This article belongs to the Special Issue Polymeric Membranes)
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