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16 pages, 2770 KiB

Open AccessArticle

Development and Characterization of Membranes with PVA Containing Silver Particles: A Study of the Addition and Stability

by Audie K. Thompson, Cannon Hackett, Tony L. Grady, Silver Enyinnia, Quincy C. Moore III and Felecia M. Nave

Polymers 2020, 12(9), 1937; https://doi.org/10.3390/polym12091937 - 27 Aug 2020

Cited by 23 | Viewed by 3614

Abstract

Developing technologies for the reduction of biofouling and enhancement of membrane functionality and durability are challenging but critical for the advancement of water purification processes. Silver (Ag) is often used in the process of purification due to its anti-fouling properties; however, the leaching [...] Read more.

Developing technologies for the reduction of biofouling and enhancement of membrane functionality and durability are challenging but critical for the advancement of water purification processes. Silver (Ag) is often used in the process of purification due to its anti-fouling properties; however, the leaching of this metal from a filtration membrane significantly reduces its effectiveness. Our study was designed to integrate the positive characteristics of poly vinyl alcohol (PVA) with the controlled incorporation of nano-scale silver ions across the membrane. This approach was designed with three goals in mind: (1) to improve antifouling activity; (2) to prevent leaching of the metal; and (3) to extend the durability of the functionalized membrane. The fabrication method we used was a modified version of manual coating in combination with sufficient pressure to ensure impregnation and proper blending of PVA with cellulose acetate. We then used the spin coater to enhance the cross-linking reaction, which improved membrane durability. Our results indicate that PVA acts as a reducing agent of Ag⁺ to Ag⁰ using X-ray photoelectron spectroscopy analysis and demonstrate that the metal retention was increased by more than 90% using PVA in combination with ultraviolet-photo-irradiated Ag+ reduced to Ag⁰. The Ag⁺ ions have sp hybrid orbitals, which accept lone pairs of electrons from a hydroxyl oxygen atom, and the covalent binding of silver to the hydroxyl groups of PVA enhanced retention. In fact, membranes with reduced Ag displayed a more effective attachment of Ag and a more efficient eradication of E. coli growth. Compared to pristine membranes, bovine serum albumin (BSA) flux increased by 8% after the initial addition of Ag and by 17% following ultraviolet irradiation and reduction of Ag, whereas BSA rejection increased by 10% and 11%, respectively. The implementation of this hybrid method for modifying commercial membranes could lead to significant savings due to increased metal retention and membrane effectiveness. These enhancements would ultimately increase the membrane’s longevity and reduce the cost/benefit ratio. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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23 pages, 8193 KiB

Open AccessArticle

Nanohybrid Membrane Synthesis with Phosphorene Nanoparticles: A Study of the Addition, Stability and Toxicity

by Joyner Eke, Philip Alexander Mills, Jacob Ryan Page, Garrison P. Wright, Olga V. Tsyusko and Isabel C. Escobar

Polymers 2020, 12(7), 1555; https://doi.org/10.3390/polym12071555 - 14 Jul 2020

Cited by 9 | Viewed by 3160

Abstract

Phosphorene is a promising candidate as a membrane material additive because of its inherent photocatalytic properties and electrical conductance which can help reduce fouling and improve membrane properties. The main objective of this study was to characterize structural and morphologic changes arising from [...] Read more.

Phosphorene is a promising candidate as a membrane material additive because of its inherent photocatalytic properties and electrical conductance which can help reduce fouling and improve membrane properties. The main objective of this study was to characterize structural and morphologic changes arising from the addition of phosphorene to polymeric membranes. Here, phosphorene was physically incorporated into a blend of polysulfone (PSf) and sulfonated poly ether ether ketone (SPEEK) doping solution. Protein and dye rejection studies were carried out to determine the permeability and selectivity of the membranes. Since loss of material additives during filtration processes is a challenge, the stability of phosphorene nanoparticles in different environments was also examined. Furthermore, given that phosphorene is a new material, toxicity studies with a model nematode, Caenorhabditis elegans, were carried out to provide insight into the biocompatibility and safety of phosphorene. Results showed that membranes modified with phosphorene displayed a higher protein rejection, but lower flux values. Phosphorene also led to a 70% reduction in dye fouling after filtration. Additionally, data showed that phosphorene loss was negligible within the membrane matrix irrespective of the pH environment. Phosphorene caused toxicity to nematodes in a free form, while no toxicity was observed for membrane permeates. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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13 pages, 2167 KiB

Open AccessArticle

Oxone^®-Mediated TEMPO-Oxidized Cellulose Nanomaterial Ultrafiltration and Dialysis Mixed-Matrix Hollow Fiber Membranes

by John P. Moore II, Kristyn Robling, Cristian Romero, Keturah Kiper, Soma Shekar Dachavaram, Peter A. Crooks and Jamie A. Hestekin

Polymers 2020, 12(6), 1348; https://doi.org/10.3390/polym12061348 - 15 Jun 2020

Cited by 3 | Viewed by 3126

Abstract

Recent exploration of cellulose nanomaterials has resulted in the creation of Oxone^®-Mediated TEMPO-Oxidized Cellulose Nanomaterials (OTO-CNMs). These materials, when incorporated into a polymer matrix, have properties showing increased flux, decreased membrane resistance, and improved clearance, making them an ideal material for [...] Read more.

Recent exploration of cellulose nanomaterials has resulted in the creation of Oxone^®-Mediated TEMPO-Oxidized Cellulose Nanomaterials (OTO-CNMs). These materials, when incorporated into a polymer matrix, have properties showing increased flux, decreased membrane resistance, and improved clearance, making them an ideal material for dialysis. This study is the first to focus on the implementation of OTO-CNMs into hollow fiber membranes and a comparison of these membranes for ultrafiltration and dialysis. Ultrafiltration and dialysis were performed using bovine serum albumin (BSA), lysozyme, and urea to analyze various properties of each hollow fiber membrane type. The results presented in this study provide the first quantitative evaluation of the clearance and sieving characteristics of Oxone^®-Mediated TEMPO-Oxidized Cellulose-Nanomaterial-doped cellulose triacetate mixed-matrix hemodialyzers. While the cellulose nanomaterials increased flux (10–30%) in ultrafiltration mode, this was offset by increased removal of albumin. However, in dialysis mode, these materials drastically increased the mass transfer of components (50–100%), which could lead to significantly lower dialysis times for patients. This change in the performance between the two different modes is most likely due to the increased porosity of the cellulose nanomaterials. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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26 pages, 6064 KiB

Open AccessEditor’s ChoiceArticle

One-Step Preparation of Antifouling Polysulfone Ultrafiltration Membranes via Modification by a Cationic Polyelectrolyte Based on Polyacrylamide

by Tatiana V. Plisko, Alexandr V. Bildyukevich, Katsiaryna S. Burts, Sergey S. Ermakov, Anastasia V. Penkova, Anna I. Kuzminova, Maria E. Dmitrenko, Tatiana A. Hliavitskaya and Mathias Ulbricht

Polymers 2020, 12(5), 1017; https://doi.org/10.3390/polym12051017 - 30 Apr 2020

Cited by 20 | Viewed by 3947

Abstract

A novel method for one-step preparation of antifouling ultrafiltration membranes via a non-solvent induced phase separation (NIPS) technique is proposed. It involves using aqueous 0.05–0.3 wt.% solutions of cationic polyelectrolyte based on a copolymer of acrylamide and 2-acryloxyethyltrimethylammonium chloride (Praestol 859) as a [...] Read more.

A novel method for one-step preparation of antifouling ultrafiltration membranes via a non-solvent induced phase separation (NIPS) technique is proposed. It involves using aqueous 0.05–0.3 wt.% solutions of cationic polyelectrolyte based on a copolymer of acrylamide and 2-acryloxyethyltrimethylammonium chloride (Praestol 859) as a coagulant in NIPS. A systematic study of the effect of the cationic polyelectrolyte addition to the coagulant on the structure, performance and antifouling stability of polysulfone membranes was carried out. The methods for membrane characterization involved scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), contact angle and zeta-potential measurements and evaluation of the permeability, rejection and antifouling performance in human serum albumin solution and surface water ultrafiltration. It was revealed that in the presence of cationic polyelectrolyte in the coagulation bath, its concentration has a major influence on the rate of “solvent–non-solvent” exchange and thus also on the rate of phase separation which significantly affects membrane structure. The immobilization of cationic polyelectrolyte macromolecules into the selective layer was confirmed by FTIR spectroscopy. It was revealed that polyelectrolyte macromolecules predominately immobilize on the surface of the selective layer and not on the bottom layer. Membrane modification was found to improve the hydrophilicity of the selective layer, to increase surface roughness and to change zeta-potential which yields the substantial improvement of membrane antifouling stability toward natural organic matter and human serum albumin. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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13 pages, 2950 KiB

Open AccessArticle

Tailoring the Thermal and Mechanical Properties of PolyActive^TM Poly(Ether-Ester) Multiblock Copolymers Via Blending with CO₂-Phylic Ionic Liquid

by Martina Klepić, Alessio Fuoco, Marcello Monteleone, Elisa Esposito, Karel Friess, Zuzana Petrusová, Pavel Izák and Johannes Carolus Jansen

Polymers 2020, 12(4), 890; https://doi.org/10.3390/polym12040890 - 12 Apr 2020

Cited by 10 | Viewed by 3436

Abstract

The last decade has seen an exponential increase in the number of studies focused on novel applications for ionic liquids (ILs). Blends of polymers with ILs have been proposed for use in fuel cells, batteries, gas separation membranes, packaging, etc., each requiring a [...] Read more.

The last decade has seen an exponential increase in the number of studies focused on novel applications for ionic liquids (ILs). Blends of polymers with ILs have been proposed for use in fuel cells, batteries, gas separation membranes, packaging, etc., each requiring a set of specific physico-chemical properties. In this work, blends of four grades of the poly(ether-ester) multiblock copolymer PolyActive™ with different concentrations of the CO₂-philic 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][Tf₂N] were prepared in the form of dense films by a solution casting and solvent evaporation method, in view of their potential use as gas separation membranes for CO₂ capture. Depending on the polymer structure, the material properties could be tailored over a wide range by means of the IL content. All samples were dry-feeling, highly elastic self-standing dense films. The microstructure of the blends was studied by scanning electron microscopy with a backscattering detector, able to observe anisotropy in the sample, while a special topographic analysis mode allowed the visualization of surface roughness. Samples with the longest poly(ethylene oxide terephthalate) (PEOT) blocks were significantly more anisotropic than those with shorter blocks, and this heterogeneity increased with increasing IL content. DSC analysis revealed a significant decrease in the melting enthalpy and melting temperature of the crystalline PEOT domains with increasing IL content, forming an amorphous phase with T_g ≈ −50 °C, whereas the polybutylene terephthalate (PBT) phase was hardly affected. This indicates better compatibility of the IL with the polyether phase than the polyester phase. Young’s modulus was highest and most IL-dependent for the sample with the highest PEOT content and PEOT block length, due to its high crystallinity. Similarly, the sample with short PEOT blocks and high PBT content also showed a high modulus and tensile strength, but much lower maximum elongation. This study provides a detailed discussion on the correlation between the morphological, thermal, and mechanical properties of these PolyActive™/[BMIM][Tf₂N] blends. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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15 pages, 3140 KiB

Open AccessArticle

Structure and Properties of PSf Hollow Fiber Membranes with Different Molecular Weight Hyperbranched Polyester Using Pentaerythritol as Core

by Min Liu, Long-Bao Zhao, Li-Yun Yu, Yong-Ming Wei and Zhen-Liang Xu

Polymers 2020, 12(2), 383; https://doi.org/10.3390/polym12020383 - 8 Feb 2020

Cited by 8 | Viewed by 3121

Abstract

A homologous series of hyperbranched polyesters (HBPEs) was successfully synthesized via an esterification reaction of 2,2-bis(methylol)propionic acid (bis-MPA) with pentaerythritol. The molecular weights of the HBPEs were 2160, 2660, 4150 and 5840 g/mol, respectively. These HBPEs were used as additives to prepare polysulfone [...] Read more.

A homologous series of hyperbranched polyesters (HBPEs) was successfully synthesized via an esterification reaction of 2,2-bis(methylol)propionic acid (bis-MPA) with pentaerythritol. The molecular weights of the HBPEs were 2160, 2660, 4150 and 5840 g/mol, respectively. These HBPEs were used as additives to prepare polysulfone (PSf) hollow fiber membranes via non-solvent induced phase separation. The characteristic behaviors of the casting solution were investigated, as well as the morphologies, hydrophilicity and mechanical properties of the PSf membranes. The results showed that the initial viscosities of the casting solutions were increased, and the shear-thinning phenomenon became increasingly obvious. The demixing rate first increased and then decreased when increasing the HBPE molecular weight, and the turning point was 2660 g/mol. The PSf hollow fiber membranes with different molecular weights of HBPEs had a co-existing morphology of double finger-like and sponge-like structures. The starting pure water contact angle decreased obviously, and the mechanical properties improved. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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16 pages, 2707 KiB

Open AccessArticle

Fabrication of Hybrid Membranes Containing Nylon-11 and Organic Semiconductor Particles with Potential Applications in Molecular Electronics

by María Elena Sánchez-Vergara, Elizabeth Guevara-Martínez, Alejandra Arreola-Castillo and Alejandra Mendoza-Sevilla

Polymers 2020, 12(1), 9; https://doi.org/10.3390/polym12010009 - 19 Dec 2019

Cited by 5 | Viewed by 4007

Abstract

Chemical degradation is a major disadvantage in the development of organic semiconductors. This work proposes the manufacture and characterization of organic semiconductor membranes in order to prevent semiconductor properties decreasing. Semiconductor membranes consisting of Nylon-11 and particles of π-conjugated molecular semiconductors were manufactured [...] Read more.

Chemical degradation is a major disadvantage in the development of organic semiconductors. This work proposes the manufacture and characterization of organic semiconductor membranes in order to prevent semiconductor properties decreasing. Semiconductor membranes consisting of Nylon-11 and particles of π-conjugated molecular semiconductors were manufactured by high-vacuum evaporation followed by thermal relaxation. Initially, and with the aim of obtaining semiconductor particles, bulk heterojunction (BHJ) was carried out using green chemistry techniques between the zinc phthalocyanine (ZnPc) and the zinc hexadecafluoro-phthalocyanine (F₁₆ZnPc) as n-type molecular semiconductors with the p-type molecular semiconductor dibenzotetrathiafulvalene (DBTTF). Consequently, the π-conjugated semiconductors particles were embedded in a Nylon-11 matrix and characterized, both structurally and considering their optical and electrical properties. Thin films of these materials were manufactured in order to comparatively study the membranes and precursor semiconductor particles. The membranes presented bandgap (E_g) values that were lower than those obtained in the films, which is an indicator of an improvement in their semiconductor capacity. Finally, the membranes were subjected to accelerated lighting conditions, to determine the stability of the polymer and the operating capacity of the membrane. After fatigue conditions, the electrical behavior of the proposed semiconductor membranes remained practically unaltered; therefore, they could have potential applications in molecular electronics. The chemical stability of membranes, which did not degrade in their polymer compound, nor in the semiconductor, was monitored by IR spectroscopy. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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20 pages, 4481 KiB

Open AccessArticle

Thiol-Affinity Immobilization of Casein-Coated Silver Nanoparticles on Polymeric Membranes for Biofouling Control

by Xiaobo Dong, Halle D. Shannon, Atena Amirsoleimani, Gail M. Brion and Isabel C. Escobar

Polymers 2019, 11(12), 2057; https://doi.org/10.3390/polym11122057 - 11 Dec 2019

Cited by 19 | Viewed by 3864

Abstract

Silver nanoparticles (AgNPs) have been widely studied for the control of biofouling on polymeric membranes due to their antimicrobial properties. However, nanoparticle leaching has posed a significant impediment against their widespread use. In this study, a one-step method of chemically embedding AgNPs on [...] Read more.

Silver nanoparticles (AgNPs) have been widely studied for the control of biofouling on polymeric membranes due to their antimicrobial properties. However, nanoparticle leaching has posed a significant impediment against their widespread use. In this study, a one-step method of chemically embedding AgNPs on cellulose acetate (CA) membranes via their affinity to thiol group chemistry was investigated. The operational efficiency of the membranes was then determined via filtration and biofouling experiments. During filtration study, the average flux values of pure CA membranes was determined to be 11 ± 2 L/(m2·hr) (LMH), while membranes embedded with AgNPs showed significant increases in flux to 18 ± 2 LMH and 25 ± 9 LMH, with increasing amounts of AgNPs added, which is likely due to the NPs acting as pore formers. Leaching studies, performed both in dead-end and crossflow filtration, showed approximately 0.16 mg/L leaching of AgNPs after the first day of filtration, but afterwards the remaining chemically-attached AgNPs did not leach. Over 97% of AgNPs remained on the membranes after seven days of crossflow leaching filtration studies. Serratia marcescens were then used as target microorganisms in biofouling studies. It was observed that membranes embedded with AgNPs effectively suppressed the growth of Serratia marcescens, and specifically, membranes with AgNPs displayed a decrease in microbial growth by 59% and 99% as the amount of AgNP increased. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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13 pages, 3984 KiB

Open AccessArticle

A Stable Anti-Fouling Coating on PVDF Membrane Constructed of Polyphenol Tannic Acid, Polyethyleneimine and Metal Ion

by Lili Wu, Qiuhu Lin, Cong Liu and Wanyu Chen

Polymers 2019, 11(12), 1975; https://doi.org/10.3390/polym11121975 - 1 Dec 2019

Cited by 21 | Viewed by 6319

Abstract

A hydrophilic and anti-fouling coating layer was constructed on a polyvinylidene fluoride (PVDF) microfiltration membrane by a novel surface modification method. The pristine membrane was firstly coated by (3-chloropropyl) trimethoxysilane/polyethyleneimine and tannic acid. Then, the metal ion was induced on the coating layer [...] Read more.

A hydrophilic and anti-fouling coating layer was constructed on a polyvinylidene fluoride (PVDF) microfiltration membrane by a novel surface modification method. The pristine membrane was firstly coated by (3-chloropropyl) trimethoxysilane/polyethyleneimine and tannic acid. Then, the metal ion was induced on the coating layer to coordinate with tannic acid and polyethyleneimine, forming a more stable and hydrophilic coating on the surface. The membrane’s surface morphology and chemical element analysis showed that the Tannic acid/ polyethyleneimine (TA/PEI) coating layer was denser and had more stability after the addition of metal ions, and this may be due to the coordination bond formed between the TA/PEI coating and metal ions. The results of the water contact angle and pure water flux measurements showed that the hydrophilicity and wettability of the modified membranes were improved obviously after introducing the metal ion layers. The anti-fouling performance and stability of the modified membrane were also characterized by the underwater oil contact angle (OCA), the separation efficiency, and the contact angle variation value for before and after the rinsing experiment. The modified membrane showed obvious stability and antifouling. Moreover, the retention rate of some composite membranes could reach 99.6%. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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20 pages, 4972 KiB

Open AccessArticle

Morphological, Electrical, and Chemical Characteristics of Poly(sodium 4-styrenesulfonate) Coated PVDF Ultrafiltration Membranes after Plasma Treatment

by Ivette G. Sandoval-Olvera, Pilar González-Muñoz, Darío R. Díaz, Ángel Maroto-Valiente, Nelio A. Ochoa, Francisco J. Carmona, Laura Palacio, José I. Calvo, Antonio Hernández, Mario Ávila-Rodríguez and Pedro Prádanos

Polymers 2019, 11(10), 1689; https://doi.org/10.3390/polym11101689 - 15 Oct 2019

Cited by 11 | Viewed by 3526

Abstract

A commercial ultrafiltration (UF) membrane (HFM-183 de Koch Membrane Systems) made of poly(vinylidene fluoride) (PVDF), was recovered with a negatively-charged polyelectrolyte (poly(sodium 4-styrenesulfonate)) (PSS), and the effects on its electric, chemical, and morphological properties were analyzed. Atomic force microscopy (AFM), liquid–liquid displacement porometry, [...] Read more.

A commercial ultrafiltration (UF) membrane (HFM-183 de Koch Membrane Systems) made of poly(vinylidene fluoride) (PVDF), was recovered with a negatively-charged polyelectrolyte (poly(sodium 4-styrenesulfonate)) (PSS), and the effects on its electric, chemical, and morphological properties were analyzed. Atomic force microscopy (AFM), liquid–liquid displacement porometry, Electrical Impedance Spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy were used to investigate the modifications induced by the deposition of PSS on the PVDF positively-charged membrane and after its treatment by a radio frequency Ar-plasma. These techniques confirmed a real deposition and posterior compaction of PSS with increasing roughness and decreasing pore sizes. The evolution of the electric resistances of the membranes confirmed crosslinking and compaction with shielding of the sulfonated groups from PSS. In this way, a membrane with a negatively-charged active layer and a pore size which was 60% lower than the original membrane was obtained. The composition of the additive used by manufacturers to modify PVDF to make it positively charged was obtained by different procedures, all of which depended upon the results of X-ray photoelectron spectroscopy, leading to fairly consistent results. This polymer, carrying positive charges, contains quaternary nitrogen, as confirmed by XPS. Moreover, Raman spectroscopy confirmed that PVDF changes from mostly the β to the α phase, which is more stable as a substrate for the deposited PSS. The aim of the tested modifications was to increase the retention of divalent anions without reducing permeability. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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15 pages, 3994 KiB

Open AccessArticle

Polymer Blends for Improved CO₂ Capture Membranes

by Alireza Zare, Lorenza Perna, Adrianna Nogalska, Veronica Ambrogi, Pierfrancesco Cerruti, Bartosz Tylkowski, Ricard García-Valls and Marta Giamberini

Polymers 2019, 11(10), 1662; https://doi.org/10.3390/polym11101662 - 12 Oct 2019

Cited by 7 | Viewed by 3441

Abstract

We investigated the possibility of improving the performance of polysulfone (PSf) membranes to be used in carbon dioxide capture devices by blending PSf with a commercial polyethylene imine, Lupasol G20, previously modified with benzoyl chloride (mG20). Additive amount ranged between 2 and 20 [...] Read more.

We investigated the possibility of improving the performance of polysulfone (PSf) membranes to be used in carbon dioxide capture devices by blending PSf with a commercial polyethylene imine, Lupasol G20, previously modified with benzoyl chloride (mG20). Additive amount ranged between 2 and 20 wt %. Membranes based on these blends were prepared by phase inversion precipitation and exhibited different morphologies with respect to neat PSf. Surface roughness, water contact angles, and water uptake increased with mG20 content. Mass transfer coefficient was also increased for both N₂ and CO₂; however, this effect was more evident for carbon dioxide. Carbon dioxide absorption performance of composite membranes was evaluated for potassium hydroxide solution in a flat sheet membrane contactor (FSMC) in cross flow module at different liquid flow rates. We found that, at the lowest flow rate, membranes exhibit a very similar behaviour to neat PSf; nevertheless, significant differences can be found at higher flow rates. In particular, the membranes with 2 and 5 wt % additive behave more efficiently than neat PSf. In contrast, 10 and 20 wt % additive content has an adverse effect on CO₂ capture when compared with neat PSf. In the former case, a combination of additive chemical affinity to CO₂ and membrane porosity can be claimed; in the latter case, the remarkably higher wettability and water uptake could determine membrane clogging and consequent loss of efficiency in the capture device. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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12 pages, 4426 KiB

Open AccessArticle

Pore Structure and Properties of PEEK Hollow Fiber Membranes: Influence of the Phase Structure Evolution of PEEK/PEI Composite

by Gong Chen, Yuan Chen, Tingjian Huang, Zhongchen He, Jianjun Xu and Pengqing Liu

Polymers 2019, 11(9), 1398; https://doi.org/10.3390/polym11091398 - 26 Aug 2019

Cited by 22 | Viewed by 5100

Abstract

Poly(ether ether ketone) (PEEK) hollow fiber membranes were successfully prepared from miscible blends of PEEK and polyetherimide (PEI) via thermally-induced phase separation (TIPS) with subsequent extraction of the PEI diluent. The phase structure evolution, extraction kinetics, membrane morphology, pore size distribution and permeability [...] Read more.

Poly(ether ether ketone) (PEEK) hollow fiber membranes were successfully prepared from miscible blends of PEEK and polyetherimide (PEI) via thermally-induced phase separation (TIPS) with subsequent extraction of the PEI diluent. The phase structure evolution, extraction kinetics, membrane morphology, pore size distribution and permeability for the hollow fiber membrane were studied in detail. Extraction experiments, differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMA) studies showed that the heat treatment had a significant influence on the two-phase structure of PEEK/PEI, and that it was controlled by the crystallization kinetic of PEEK and the diffusion kinetic of PEI. As the annealing temperature increased, the controlling factor of the phase separation changed from PEEK crystallization to PEI diffusion, and the main distribution of the amorphous PEI chains were changed from the interlamellar region to the interfibrillar or interspherulitic regions of PEEK crystallization. When the annealing temperature increased from 240 °C to 280 °C, the extracted amount of PEI increased from 85.19 to 96.24 wt %, and the pore diameter of PEEK membrane increased from 10.59 to 37.85 nm, while the surface area of the PEEK membrane decreased from 111.9 to 83.69 m²/g. Moreover, the water flux of the PEEK hollow fiber membranes increased from 1.91 × 10⁻² to 1.65 × 10⁻¹ L h⁻¹ m⁻² bar⁻¹ as the annealing temperature increased from 240 °C to 270 °C. The structure and properties of the PEEK hollow fiber membrane can be effectively controlled by regulating heat treatment conditions. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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15 pages, 3516 KiB

Open AccessArticle

Floating-on-water Fabrication Method for Thin Polydimethylsiloxane Membranes

by Daehan Kim, Sung-Hwan Kim and Joong Yull Park

Polymers 2019, 11(8), 1264; https://doi.org/10.3390/polym11081264 - 31 Jul 2019

Cited by 22 | Viewed by 6821

Abstract

Polydimethylsiloxane (PDMS) membranes are used in various applications, such as microvalves, micropumps, microlenses, and cell culture substrates, with various thicknesses from microscale to nanoscale. In this study, we propose a simple fabrication method for PDMS membranes on a water surface, referred to as [...] Read more.

Polydimethylsiloxane (PDMS) membranes are used in various applications, such as microvalves, micropumps, microlenses, and cell culture substrates, with various thicknesses from microscale to nanoscale. In this study, we propose a simple fabrication method for PDMS membranes on a water surface, referred to as the floating-on-water (FoW) method. FoW can be used to easily fabricate PDMS membranes with thicknesses of a few micrometers (minimum 3 μm) without special equipment. In addition, as the membrane is fabricated on the water surface, it can be easily handled without damage. In addition, alternative membrane structures were demonstrated, such as membrane-on-pins and droplet-shaped membranes. FoW can be widely used in various applications that require PDMS membranes with microscale thicknesses. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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18 pages, 6388 KiB

Open AccessArticle

Investigations on the Properties and Performance of Mixed-Matrix Polyethersulfone Membranes Modified with Halloysite Nanotubes

by Sylwia Mozia, Amanda Grylewicz, Michał Zgrzebnicki, Dominika Darowna and Adam Czyżewski

Polymers 2019, 11(4), 671; https://doi.org/10.3390/polym11040671 - 11 Apr 2019

Cited by 27 | Viewed by 4177

Abstract

Ultrafiltration (UF) polyethersulfone (PES) membranes were prepared by wet phase inversion method. Commercial halloysite nanotubes (HNTs) in the amount of 0.5–4 wt % vs PES (15 wt %) were introduced into the casting solution containing the polymer and N,N-dimethylformamide as [...] Read more.

Ultrafiltration (UF) polyethersulfone (PES) membranes were prepared by wet phase inversion method. Commercial halloysite nanotubes (HNTs) in the amount of 0.5–4 wt % vs PES (15 wt %) were introduced into the casting solution containing the polymer and N,N-dimethylformamide as a solvent. The morphology, physicochemical properties and performance of the membranes were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM), zeta potential, porosity and contact angle analyses, as well as permeability measurements. Moreover, the antifouling properties of the membranes were evaluated during UF of a model solution of bovine serum albumin (BSA). The research revealed a positive influence of modification with HNTs on hydrophilicity, water permeability and antifouling properties of the PES membranes. The most significant improvement of permeability was obtained in case of the membrane containing 2 wt % of HNTs, whereas the highest fouling resistance was observed for 0.5 wt % HNTs content. It was found that a good dispersion of HNTs can be obtained only at loadings below 2 wt %. Based on the results a relation between severity of membrane fouling and surface roughness was proved. Moreover, an increase of the roughness of the modified membranes was found to be accompanied by an increase of isoelectric point values. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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Review

Jump to: Research

35 pages, 6505 KiB

Open AccessReview

Review on Blueprint of Designing Anti-Wetting Polymeric Membrane Surfaces for Enhanced Membrane Distillation Performance

by Saikat Sinha Ray, Hyung-Kae Lee and Young-Nam Kwon

Polymers 2020, 12(1), 23; https://doi.org/10.3390/polym12010023 - 20 Dec 2019

Cited by 44 | Viewed by 5847

Abstract

Recently, membrane distillation (MD) has emerged as a versatile technology for treating saline water and industrial wastewater. However, the long-term use of MD wets the polymeric membrane and prevents the membrane from working as a semi-permeable barrier. Currently, the concept of antiwetting interfaces [...] Read more.

Recently, membrane distillation (MD) has emerged as a versatile technology for treating saline water and industrial wastewater. However, the long-term use of MD wets the polymeric membrane and prevents the membrane from working as a semi-permeable barrier. Currently, the concept of antiwetting interfaces has been utilized for reducing the wetting issue of MD. This review paper discusses the fundamentals and roles of surface energy and hierarchical structures on both the hydrophobic characteristics and wetting tolerance of MD membranes. Designing stable antiwetting interfaces with their basic working principle is illustrated with high scientific discussions. The capability of antiwetting surfaces in terms of their self-cleaning properties has also been demonstrated. This comprehensive review paper can be utilized as the fundamental basis for developing antiwetting surfaces to minimize fouling, as well as the wetting issue in the MD process. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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26 pages, 3559 KiB

Open AccessReview

Advances on Non-Genetic Cell Membrane Engineering for Biomedical Applications

by Lisha Liu, Hongliang He and Jianping Liu

Polymers 2019, 11(12), 2017; https://doi.org/10.3390/polym11122017 - 5 Dec 2019

Cited by 12 | Viewed by 6644

Abstract

Cell-based therapeutics are very promising modalities to address many unmet medical needs, including genetic engineering, drug delivery, and regenerative medicine as well as bioimaging. To enhance the function and improve the efficacy of cell-based therapeutics, a variety of cell surface engineering strategies (genetic [...] Read more.

Cell-based therapeutics are very promising modalities to address many unmet medical needs, including genetic engineering, drug delivery, and regenerative medicine as well as bioimaging. To enhance the function and improve the efficacy of cell-based therapeutics, a variety of cell surface engineering strategies (genetic engineering and non-genetic engineering) are developed to modify the surface of cells or cell-based therapeutics with some therapeutic molecules, artificial receptors, and multifunctional nanomaterials. In comparison to complicated procedures and potential toxicities associated with genetic engineering, non-genetic engineering strategies have emerged as a powerful and compatible complement to traditional genetic engineering strategies for enhancing the function of cells or cell-based therapeutics. In this review, we will first briefly summarize key non-genetic methodologies including covalent chemical conjugation (surface reactive groups–direct conjugation, and enzymatically mediated and metabolically mediated indirect conjugation) and noncovalent physical bioconjugation (biotinylation, electrostatic interaction, and lipid membrane fusion as well as hydrophobic insertion), which have been developed to engineer the surface of cell-based therapeutics with various materials. Next, we will comprehensively highlight the latest advances in non-genetic cell membrane engineering surrounding different cells or cell-based therapeutics, including whole-cell-based therapeutics, cell membrane-derived therapeutics, and extracellular vesicles. Advances will be focused specifically on cells that are the most popular types in this field, including erythrocytes, platelets, cancer cells, leukocytes, stem cells, and bacteria. Finally, we will end with the challenges, future trends, and our perspectives of this relatively new and fast-developing research field. Full article

(This article belongs to the Special Issue Advances in Polymeric Membranes)

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