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19 pages, 4633 KiB

Open AccessArticle

Nanocomposite Membranes for PEM-FCs: Effect of LDH Introduction on the Physic-Chemical Performance of Various Polymer Matrices

by Muhammad Habib Ur Rehman, Ernestino Lufrano and Cataldo Simari

Polymers 2023, 15(3), 502; https://doi.org/10.3390/polym15030502 - 18 Jan 2023

Cited by 4 | Viewed by 1367

Abstract

This is a comparative study to clarify the effect of the introduction of layered double hydroxide (LDH) into various polymer matrices. One perfluorosulfonic acid polymer, i.e., Nafion, and two polyaromatic polymers such as sulfonated polyether ether ketone (sPEEK) and sulfonated polysulfone (sPSU), were [...] Read more.

This is a comparative study to clarify the effect of the introduction of layered double hydroxide (LDH) into various polymer matrices. One perfluorosulfonic acid polymer, i.e., Nafion, and two polyaromatic polymers such as sulfonated polyether ether ketone (sPEEK) and sulfonated polysulfone (sPSU), were used for the preparation of nanocomposite membranes at 3 wt.% of LDH loading. Thereafter, the PEMs were characterized by X-ray diffraction (XRD) and dynamic mechanical analysis (DMA) for their microstructural and thermomechanical features, whereas water dynamics and proton conductivity were investigated by nuclear magnetic resonance (PFG and T₁) and EIS spectroscopies, respectively. Depending on the hosting matrix, the LDHs can simply provide additional hydrophilic sites or act as physical crosslinkers. In the latter case, an impressive enhancement of both dimensional stability and electrochemical performance was observed. While pristine sPSU exhibited the lowest proton conductivity, the sPSU/LDH nanocomposite was able to compete with Nafion, yielding a conductivity of 122 mS cm⁻¹ at 120 °C and 90% RH with an activation energy of only 8.7 kJ mol⁻¹. The outcome must be ascribed to the mutual and beneficial interaction of the LDH nanoplatelets with the functional groups of sPSU, therefore the choice of the appropriate filler is pivotal for the preparation of highly-performing composites. Full article

(This article belongs to the Special Issue Progress in Polymer Membranes and Films)

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14 pages, 4132 KiB

Open AccessArticle

Effects of Co-Solvent-Induced Self-Assembled Graphene-PVDF Composite Film on Piezoelectric Application

by Januar Widakdo, Wen-Ching Lei, Anawati Anawati, Subrahmanya Thagare Manjunatha, Hannah Faye M. Austria, Owen Setiawan, Tsung-Han Huang, Yu-Hsuan Chiao, Wei-Song Hung and Ming-Hua Ho

Polymers 2023, 15(1), 137; https://doi.org/10.3390/polym15010137 - 28 Dec 2022

Cited by 4 | Viewed by 2067

Abstract

A persistent purpose for self-powered and wearable electronic devices is the fabrication of graphene-PVDF piezoelectric nanogenerators with various co-solvents that could provide enhanced levels of durability and stability while generating a higher output. This study resulted in a piezoelectric nanogenerator based on a [...] Read more.

A persistent purpose for self-powered and wearable electronic devices is the fabrication of graphene-PVDF piezoelectric nanogenerators with various co-solvents that could provide enhanced levels of durability and stability while generating a higher output. This study resulted in a piezoelectric nanogenerator based on a composite film composed of graphene, and poly (vinylidene fluoride) (PVDF) as a flexible polymer matrix that delivers high performance, flexibility, and cost-effectiveness. By adjusting the co-solvent in the solution, a graphene-PVDF piezoelectric nanogenerator can be created (acetone, THF, water, and EtOH). The solution becomes less viscous and is more diluted the more significant the concentration of co-solvents, such as acetone, THF, and EtOH. Additionally, when the density is low, the thickness will be thinner. The final film thickness for all is ~25 µm. Furthermore, the- crystal phase becomes more apparent when graphene is added and combined with the four co-solvents. Based on the XRD results, the peak changes to the right, which can be inferred to be more dominant with the β-phase. THF is the co-solvent with the highest piezoelectric output among other co-solvents. Most of the output voltages produced are 0.071 V and are more significant than the rest. Full article

(This article belongs to the Special Issue Progress in Polymer Membranes and Films)

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11 pages, 3337 KiB

Open AccessArticle

Preparation and Characterization of Polyvinylalcohol/Polysulfone Composite Membranes for Enhanced CO₂/N₂ Separation

by Ying Li, Danlin Chen and Xuezhong He

Polymers 2023, 15(1), 124; https://doi.org/10.3390/polym15010124 - 28 Dec 2022

Cited by 6 | Viewed by 6042

Abstract

The unique properties of polyvinyl alcohol (PVA) and polysulfone (PSf), such as good membrane-forming ability and adjustable structure, provide a great opportunity for CO₂-separation membrane development. This work focuses on the fabrication of PVA/PSf composite membranes for CO₂/N₂ [...] Read more.

The unique properties of polyvinyl alcohol (PVA) and polysulfone (PSf), such as good membrane-forming ability and adjustable structure, provide a great opportunity for CO₂-separation membrane development. This work focuses on the fabrication of PVA/PSf composite membranes for CO₂/N₂ separations. The membranes prepared by coating a 7.5 wt% PVA on top of PSf substrate showed a relatively thin selective layer of 1.7 µm with an enhanced CO₂/N₂ selectivity of 78, which is a ca. 200% increase compared to the pure PSf membranes. The CO₂/N₂ selectivity decreases at a rapid rate with the increase of feed pressure from 1.8 to 5 bar, while the CO₂ permeance shows a slight reduction, which is caused by the weakening of coupling transportation between water and CO₂ molecules, as well as membrane compaction at higher pressures. Increasing operating temperature from 22 °C to 50 °C leads to a slight decrease in CO₂ permeance, but a significant reduction in the CO₂/N₂ selectivity from 78 to 27.1. Moreover, the mass transfer coefficient of gas molecules is expected to increase at a higher velocity, which leads to the increase of CO₂ permeance at higher feed flow rates. It was concluded that the CO₂ separation performance of the prepared membranes was significantly dependent on the membrane operating parameters, and process design and optimization are crucial to bringing CO₂-separation membranes for industrial applications in post-combustion carbon capture. Full article

(This article belongs to the Special Issue Progress in Polymer Membranes and Films)

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12 pages, 3889 KiB

Open AccessArticle

Electrospun Polycaprolactone/ZnO Nanocomposite Membranes with High Antipathogen Activity

by Elizaveta S. Permyakova, Anton M. Manakhov, Philipp V. Kiryukhantsev-Korneev, Denis V. Leybo, Anton S. Konopatsky, Yulia A. Makarets, Svetlana Yu. Filippovich, Sergey G. Ignatov and Dmitry V. Shtansky

Polymers 2022, 14(24), 5364; https://doi.org/10.3390/polym14245364 - 08 Dec 2022

Cited by 8 | Viewed by 1667

Abstract

The spread of bacterial, fungal, and viral diseases by airborne aerosol flows poses a serious threat to human health, so the development of highly effective antibacterial, antifungal and antiviral filters to protect the respiratory system is in great demand. In this study, we [...] Read more.

The spread of bacterial, fungal, and viral diseases by airborne aerosol flows poses a serious threat to human health, so the development of highly effective antibacterial, antifungal and antiviral filters to protect the respiratory system is in great demand. In this study, we developed ZnO-modified polycaprolactone nanofibers (PCL-ZnO) by treating the nanofiber surface with plasma in a gaseous mixture of Ar/CO₂/C₂H₄ followed by the deposition of ZnO nanoparticles (NPs). The structure and chemical composition of the composite fibers were characterized by SEM, TEM, EDX, FTIR, and XPS methods. We demonstrated high material stability. The mats were tested against Gram-positive and Gram-negative pathogenic bacteria and pathogenic fungi and demonstrated high antibacterial and antifungal activity. Full article

(This article belongs to the Special Issue Progress in Polymer Membranes and Films)

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9 pages, 2409 KiB

Open AccessArticle

Electrospinning Technique for Fabrication of Coaxial Nanofibers of Semiconductive Polymers

by William Serrano-Garcia, Seeram Ramakrishna and Sylvia W. Thomas

Polymers 2022, 14(23), 5073; https://doi.org/10.3390/polym14235073 - 22 Nov 2022

Cited by 7 | Viewed by 1649

Abstract

In this work, the electrospinning technique is used to fabricate a polymer-polymer coaxial structure nanofiber from the p-type regioregular polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) and the n-type conjugated ladder polymer poly(benzimidazobenzophenanthroline) (BBL) of orthogonal solvents. Generally, the fabrication of polymeric coaxial nanostructures tends to be [...] Read more.

In this work, the electrospinning technique is used to fabricate a polymer-polymer coaxial structure nanofiber from the p-type regioregular polymer poly(3-hexylthiophene-2,5-diyl) (P3HT) and the n-type conjugated ladder polymer poly(benzimidazobenzophenanthroline) (BBL) of orthogonal solvents. Generally, the fabrication of polymeric coaxial nanostructures tends to be troublesome. Using the electrospinning technique, P3HT was successfully used as the core, and the BBL as the shell, thus conceptually forming a p-n junction that is cylindrical in form with diameters in a range from 280 nm to 2.8 µm. The UV–VIS of P3HT/PS blend solution showed no evidence of separation or precipitation, while the combined solutions of P3HT/PS and BBL were heterogeneous. TEM images show a well-formed coaxial structure that is normally not expected due to rapid reaction and solidification when mixed in vials in response to orthogonal solubility. For this reason, extruding it by using electrostatic forces promoted a quick elongation of the polymers while forming a concise interface. Single nanofiber electrical characterization demonstrated the conductivity of the coaxial surface of ~1.4 × 10⁻⁴ S/m. Furthermore, electrospinning has proven to be a viable method for the fabrication of pure semiconducting coaxial nanofibers that can lead to the desired fabrication of fiber-based electronic devices. Full article

(This article belongs to the Special Issue Progress in Polymer Membranes and Films)

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11 pages, 3165 KiB

Open AccessArticle

Hollow TiO₂/Poly (Vinyl Pyrrolidone) Fibers Obtained via Coaxial Electrospinning as Easy-to-Handle Photocatalysts for Effective Nitrogen Oxide Removal

by Juran Kim

Polymers 2022, 14(22), 4942; https://doi.org/10.3390/polym14224942 - 15 Nov 2022

Cited by 2 | Viewed by 992

Abstract

Herein, we present a method for fabricating hollow TiO₂ microfibers from Ti (OBu)₄/poly (vinyl pyrrolidone) sol-gel precursors and their effects on denitrification as a photocatalyst for air purification. Various sizes of hollow TiO₂ fibers were developed using coaxial electrospinning [...] Read more.

Herein, we present a method for fabricating hollow TiO₂ microfibers from Ti (OBu)₄/poly (vinyl pyrrolidone) sol-gel precursors and their effects on denitrification as a photocatalyst for air purification. Various sizes of hollow TiO₂ fibers were developed using coaxial electrospinning by controlling the core flow rate from 0 to 3 mL h⁻¹. At higher flow rates, the wall layer was thinner, and outer and core diameters were larger. These features are correlated with physical properties, including specific surface area, average pore diameter, and crystalline structure. The increase in the core flow rate from 0 to 3 mL h⁻¹ leads to a corresponding increase in the specific surface area from 1.81 to 3.95 µm and a decrease in the average pore diameter from 28.9 to 11.1 nm. Furthermore, the increased core flow rate results in a high anatase and rutile phase content in the structure. Herein, hollow TiO₂ was produced with an approximately equal content of anatase/rutile phases with few impurities. A flow rate of 3 mL h⁻¹ resulted in the highest specific surface area of 51.28 m² g⁻¹ and smallest pore diameter size of ~11 nm, offering more active sites at the fiber surface for nitrogen oxide removal of up to 66.2% from the atmosphere. Full article

(This article belongs to the Special Issue Progress in Polymer Membranes and Films)

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14 pages, 2476 KiB

Open AccessArticle

A Comparative Study of PMETAC-Modified Mesoporous Silica and Titania Thin Films for Molecular Transport Manipulation

by Sebastian Alberti, Juan Giussi, Omar Azzaroni and Galo J. A. A. Soler-Illia

Polymers 2022, 14(22), 4823; https://doi.org/10.3390/polym14224823 - 09 Nov 2022

Cited by 3 | Viewed by 1512

Abstract

The manipulation and understanding of molecular transport across functionalized nanopores will take us closer to mimicking biological membranes and thus to design high-performance permselective separation systems. In this work, Surface-initiated atom transfer radical polymerization (SI-ATRP) of (2-methacryloyloxy)-ethyltrimethylammonium chloride (METAC) was performed on both [...] Read more.

The manipulation and understanding of molecular transport across functionalized nanopores will take us closer to mimicking biological membranes and thus to design high-performance permselective separation systems. In this work, Surface-initiated atom transfer radical polymerization (SI-ATRP) of (2-methacryloyloxy)-ethyltrimethylammonium chloride (METAC) was performed on both mesoporous silica and mesoporous titania thin films. Pores were proven to be filled using ellipsometry and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Furthermore, the employed method leads to a polymer overlayer, whose thickness could be discriminated using a double-layer ellipsometry model. Cyclic voltammetry experiments reveal that the transport of electrochemically active probes is affected by the PMETAC presence, both due to the polymer overlayer and the confined charge of the pore-tethered PMETAC. A more detailed study demonstrates that ion permeability depends on the combined role of the inorganic scaffolds’ (titania and silica) surface chemistry and the steric and charge exclusion properties of the polyelectrolyte. Interestingly, highly charged negative walls with positively charged polymers may resemble zwitterionic polymer behavior in confined environments. Full article

(This article belongs to the Special Issue Progress in Polymer Membranes and Films)

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12 pages, 12476 KiB

Open AccessArticle

Preparing Hydrophobic Cellulose Nanofibers-SiO₂ Films and Coating by One-Step Mechanochemical Method

by Xi Chen, Lijiaqi Zhang, Min Wu and Yong Huang

Polymers 2022, 14(20), 4413; https://doi.org/10.3390/polym14204413 - 19 Oct 2022

Cited by 2 | Viewed by 2531

Abstract

Green and sustainable cellulose-based hydrophobic coatings are increasingly the subject of scientific and industrial research. However, few researchers pay attention to preparing it by a one-step method. Therefore, a superhydrophobic coating composed of hydrophobic SiO₂ and cellulose nanofiber modified by 3,4-dichlorophenyl isocyanate [...] Read more.

Green and sustainable cellulose-based hydrophobic coatings are increasingly the subject of scientific and industrial research. However, few researchers pay attention to preparing it by a one-step method. Therefore, a superhydrophobic coating composed of hydrophobic SiO₂ and cellulose nanofiber modified by 3,4-dichlorophenyl isocyanate was manufactured through one-step ball milling. It was found that the ball milling can promote SiO₂ dispersion and achieve the preparation of modified nanocellulose, which further disperse SiO₂ nanoparticles to form film or coating. Compared with the ultrasonic dispersion method, the composite coating prepared by ball milling method can obtain higher water contact angle and more stable hydrophobic properties. The hydrophobic cellulose nanofiber can load 1.5 equivalents of SiO₂ nanoparticles to form a uniform film with the water contact angle of 158.0° and low moisture absorption. When this nanocomposite is used as a coating material, it can impart super-hydrophobicity to paper surface with water contact angle of 155.8°. This work provides a facile way to prepare superhydrophobic nanocellulose/nanoparticles composite coatings and films, thereby broadening the ways of dispersing nanoparticles and constructing superhydrophobic coatings. Full article

(This article belongs to the Special Issue Progress in Polymer Membranes and Films)

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11 pages, 1643 KiB

Open AccessArticle

Influence of Ulluco Starch Modified by Annealing on the Physicochemical Properties of Biodegradable Films

by Luis Daniel Daza, Daniela O. Parra, Carmen Rosselló, Walter Murillo Arango, Valeria Soledad Eim and Henry Alexander Váquiro

Polymers 2022, 14(20), 4251; https://doi.org/10.3390/polym14204251 - 11 Oct 2022

Cited by 3 | Viewed by 1516

Abstract

This work aimed to evaluate the use of annealing (ANN) ulluco starch in the preparation of biodegradable films and its impact on the physicochemical properties of the materials. Three film samples (FS1, FS2, and FS3) were prepared at a fixed starch concentration (2.6% [...] Read more.

This work aimed to evaluate the use of annealing (ANN) ulluco starch in the preparation of biodegradable films and its impact on the physicochemical properties of the materials. Three film samples (FS1, FS2, and FS3) were prepared at a fixed starch concentration (2.6% w/v) using glycerol as a plasticizer and then compared to a control sample (FSC) prepared with native ulluco starch. The physical, mechanical, and thermal properties of the films were evaluated. The use of ANN starch decreased the solubility (from 21.8% to 19.5%) and the swelling power (from 299% to 153%) of the film samples. In addition, an increase in opacity and relative crystallinity (from 7.54% to 10.5%) were observed. Regarding the thermal properties, all the samples presented high stability to degradation, with degradation temperatures above 200 °C. However, the samples showed deficiencies in their morphology, which affected the barrier properties. The use of ANN starch has some advantages over native starch in preparing films. However, more analysis is needed to improve the barrier properties of the materials. This work reveals the potential of the ANN ulluco starch for biodegradable film preparation. In addition, the use of modified ulluco starch is an alternative to add value to the crop, as well as to replace non-biodegradable materials used in the preparation of packaging. Full article

(This article belongs to the Special Issue Progress in Polymer Membranes and Films)

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15 pages, 4569 KiB

Open AccessArticle

On the Thermochemical Transition Depression of Cellulose Acetate Composite Membranes

by Costas Tsioptsias, George-Romanos P. Foukas, Savvina-Maria Papaioannou, Evangelos Tzimpilis and Ioannis Tsivintzelis

Polymers 2022, 14(16), 3434; https://doi.org/10.3390/polym14163434 - 22 Aug 2022

Cited by 9 | Viewed by 1792

Abstract

Gallic acid (GA) and quercetin (QU) are two important bioactive molecules with increased biomedical interest. Cellulose acetate (CA) is a polymer derived from cellulose and is used in various applications. In this work, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform [...] Read more.

Gallic acid (GA) and quercetin (QU) are two important bioactive molecules with increased biomedical interest. Cellulose acetate (CA) is a polymer derived from cellulose and is used in various applications. In this work, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) were used to study the thermal behavior of electrospun CA membranes loaded with quercetin or gallic acid. It was found that gallic acid and quercetin depress the thermochemical transition (simultaneous softening and decomposition) of CA, in a mechanism similar to that of the glass transition depression of amorphous polymers by plasticizers. The extensive hydrogen bonding, besides the well-known effect of constraining polymer’s softening by keeping macromolecules close to each other, has a secondary effect on the thermochemical transition, i.e., it weakens chemical bonds and, inevitably, facilitates decomposition. This second effect of hydrogen bonding can provide an explanation for an unexpected observation of this study: CA membranes loaded with quercetin or gallic acid soften at lower temperatures; however, at the same time, they decompose to a higher extent than pure CA. Besides optimization of CA processing, the fundamental understanding of the thermochemical transition depression could lead to the design of more sustainable processes for biomass recycling and conversion. Full article

(This article belongs to the Special Issue Progress in Polymer Membranes and Films)

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8 pages, 1993 KiB

Open AccessCommunication

Gradient Porous Structured MnO₂-Nonwoven Composite: A Binder-Free Polymeric Air Filter for Effective Room-Temperature Formaldehyde Removal

by Zijian Dai, Jianyong Yu and Yang Si

Polymers 2022, 14(12), 2504; https://doi.org/10.3390/polym14122504 - 20 Jun 2022

Cited by 4 | Viewed by 2049

Abstract

Recently, MnO₂-coated polymeric filters have shown promising performance in room-temperature formaldehyde abatement. However, a commonly known concern of MnO₂/polymer composites is either MnO₂ crystal encapsulation or weak adhesion. This work reports a low-cost high-throughput and green strategy to [...] Read more.

Recently, MnO₂-coated polymeric filters have shown promising performance in room-temperature formaldehyde abatement. However, a commonly known concern of MnO₂/polymer composites is either MnO₂ crystal encapsulation or weak adhesion. This work reports a low-cost high-throughput and green strategy to produce binder-free MnO₂-nonwoven composite air filters. The production approach is energy saving and environmentally friendly, which combines MnO₂ crystal coating on bicomponent polyolefin spunbond nonwovens and subsequent heat immobilizing of crystals, followed by the removal of weakly bonded MnO₂. The binder-free MnO₂-nonwoven composites show firm catalyst-fiber adhesion, a gradient porous structure, and excellent formaldehyde removal capability (94.5% ± 0.4%) at room temperature, and the reaction rate constant is 0.040 min⁻¹. In contrast to the MnO₂-nonwoven composites containing organic binders, the HCHO removal of binder-free filters increased by over 4%. This study proposes an alternative solution in producing catalyst/fabric composite filters for formaldehyde removal. Full article

(This article belongs to the Special Issue Progress in Polymer Membranes and Films)

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Review

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26 pages, 7475 KiB

Open AccessReview

Construction and Ion Transport-Related Applications of the Hydrogel-Based Membrane with 3D Nanochannels

by Yushuang Hou, Shuhui Ma, Jinlin Hao, Cuncai Lin, Jiawei Zhao and Xin Sui

Polymers 2022, 14(19), 4037; https://doi.org/10.3390/polym14194037 - 27 Sep 2022

Cited by 7 | Viewed by 2202

Abstract

Hydrogel is a type of crosslinked three-dimensional polymer network structure gel. It can swell and hold a large amount of water but does not dissolve. It is an excellent membrane material for ion transportation. As transport channels, the chemical structure of hydrogel can [...] Read more.

Hydrogel is a type of crosslinked three-dimensional polymer network structure gel. It can swell and hold a large amount of water but does not dissolve. It is an excellent membrane material for ion transportation. As transport channels, the chemical structure of hydrogel can be regulated by molecular design, and its three-dimensional structure can be controlled according to the degree of crosslinking. In this review, our prime focus has been on ion transport-related applications based on hydrogel materials. We have briefly elaborated the origin and source of hydrogel materials and summarized the crosslinking mechanisms involved in matrix network construction and the different spatial network structures. Hydrogel structure and the remarkable performance features such as microporosity, ion carrying capability, water holding capacity, and responsiveness to stimuli such as pH, light, temperature, electricity, and magnetic field are discussed. Moreover, emphasis has been made on the application of hydrogels in water purification, energy storage, sensing, and salinity gradient energy conversion. Finally, the prospects and challenges related to hydrogel fabrication and applications are summarized. Full article

(This article belongs to the Special Issue Progress in Polymer Membranes and Films)

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