Quaternized Poly Vinyl Alcohol Research Articles

Semi-interpenetrating network anion exchange membranes based on quaternized polyvinyl alcohol/poly(diallyldimethylammonium chloride)

The semi-interpenetrating network anion exchange membranes (AEMs) based on quaternized polyvinyl alcohol (QPVA) and poly(diallyldimethylammonium chloride) (PDDA) are synthesized. The chemical cross-linking structure is formed between hydroxyl groups of QPVA and aldehyde groups of glutaraldehyde (GA), which makes PDDA more stable embed in the QPVA matrix and also improves the mechanical properties and dimensional stability of AEMs. Due to the phase separation phenomenon of AEMs swelling in water, a microporous structure may be formed in the membrane, which reduces the transmission resistance of hydroxide ions and provides a larger space for the transfer of hydroxide ions, thus improving the conductivity. The ring structure of PDDA is introduced as a cationic group to transfer hydroxide ions, and shields the nucleophilic attack of the hydroxide ions through the steric hindrance effect, which improves alkaline stability. The hydroxide conductivity of semi-interpenetrating network membrane (QPVA/PDDA0.5-GA) is 36.5 mS cm−1 at 60 °C. And the membrane of QPVA/PDDA0.5-GA exhibits excellent mechanical property with maximum tensile strength of 19.6 MPa. After immersing into hot 3 mol L−1 NaOH solutions at 60 °C for 300 h, the OH− conductivity remains 78% of its initial value. The semi-interpenetrating network AEMs with microporous structure exhibit good ionic conductivity, mechanical strength and alkaline durability.

Evaluation of Quaternized polyvinyl alcohol/graphene oxide‐based membrane towards improving the performance of air‐breathing passive direct methanol fuel cells

Graphene oxide (GO) nanosheets are introduced to a Quaternized polyvinyl alcohol (QPVA) polymer matrix to obtain an anion exchange membranes (AEMs) for application of fuel cells. QPVA/GO nanocomposite membranes provide desirable properties such as low fuel uptake and permeability, excellent ionic conductivity, and cell performance, all of which are favorable for AEMs based on our previous works. Passive direct methanol fuel cells (DMFCs) are recognized as suitable technologies for use in portable devices. Nevertheless, the commercialization of DMFCs remains restricted due to a number of issues related to the conventional membrane; one of these issues is high fuel crossover problems due to high fuel uptake and permeability of Nafion membrane. This study aimed to expand the potential applications of QPVA/GO nanocomposite membranes in air-breathing passive DMFCs. The ionic conductivity, methanol uptakes (MUs), and permeabilities of self-synthesis QPVA/GO nanocomposites are examined to evaluate the ability to operate in methanol atmosphere. At 30°C, the ionic conductivity of the membranes reached 1.74 × 10−2 S cm−1. The MUs and permeabilities were as low as 35% and 7.6 × 10−7 cm2 s−1, respectively. The performance of air-breathing passive DMFCs bearing QPVA/GO nanocomposite membrane is much higher compared to conventional membranes. The maximum power density of air-breathing passive DMFCs was achieved 27.2 mW cm−2 under the optimum condition of 2 M methanol + 4 M KOH at 70°C. Single-cells could be sustained for 1000 hours. This article is the first to optimize and highlight the performance air-breathing passive DMFCs by using a QPVA-based membrane.

A review of quaternized polyvinyl alcohol as an alternative polymeric membrane in DMFCs and DEFCs

Direct methanol fuel cells (DMFCs) and direct ethanol fuel cells (DEFCs) have emerged as alternative power generators for portable devices and household appliances because of their easy and fast production of electricity, as well as high energy conversion to provide high-power density. However, several critical factors limit the commercialization of DMFCs and DEFCs, particularly issues related to polymer electrolyte membranes, including the high-cost production of Nafion membranes and cell degradation caused by high fuel crossover and dehydration. This review paper provides an overview of the current status and challenges in quaternized polyvinyl alcohol (QPVA)-based membranes as an alternative polymer electrolyte membrane for DMFCs and DEFCs. The main advantages of using QPVA-based membranes in fuel cells are reduced cost production of membrane, fuel-crossover minimization, and competitive conductivity with Nafion membrane. The effects of modifying the QPVA-based membrane, especially on conductivity properties, fuel crossover, uptake condition, mechanical, thermal, and chemical properties, and single-cell performance are comprehensively discussed. The best performances of DMFCs and DEFCs with utilizing QPVA-based membrane are reported as 272 and 144 mW cm−2, respectively. This paper is the first to highlight the current status and challenges of QPVA-based membranes for DMFCs and DEFCs applications.

Preparation of water-based anion-exchange membrane from PVA for anti-fouling in the electrodialysis process

Anion exchange membrane (AEMs) fouling is a serious problem influencing membrane performance during electrodialysis process(ED), which would increase power consumption and reduce water recovery. In this paper, an aliphatic anion-exchange membrane was prepared from quaternized polyvinyl alcohol (QPVA) via dual cross-linking through annealing treatment and condensation reaction to restrain the membrane water swelling. The Wu% of QPVA membrane could be reduced to 22.87 ± 0.81%. Due to the hydrophilia (59.86 ± 0.21°), negative ζ-potential surface and aliphatic matrix of QPVA, no transition time appeared under our experiment condition, indicating the QPVA membrane was scarcely fouled by SDBS. And the existence of SDBS in dilute solution generated slightly effect on the QPVA membrane resistance and only 7.47 ± 0.21% reduction of the desalination rate in ED process. Furthermore, only distilled water was used as solution or reaction media, without any harmful organic solvents, presenting an environmentally friendly route for the preparation of water-based anion-exchange membrane. So, the excellent anti-fouling performance along with green preparation of QPVA showed its remarkable prospect for desalination purpose in ED process.

Magnetic field-assisted alignment of graphene oxide nanosheets in a polymer matrix to enhance ionic conduction

This study aims to elucidate the effect of magnetic graphene oxide (GO) alignment in a polymer matrix on the ionic conduction and methanol barrier properties of the resulting composites. Magnetic iron oxide (Fe3O4) nanoparticles were fabricated and anchored on GO nanosheets. The magnetic GO-Fe3O4 nanofillers were incorporated into a quaternized polyvinyl alcohol (QPVA) matrix to form a polymeric composite. By applying a magnetic field (MF) along the in-plane direction during the drying and film formation steps, the GO-Fe3O4 nanosheets were aligned in an orientation parallel to the direction of the MF and connected to each other in elongated domains, as confirmed using transmission electron microscopy, field emission scanning electron microscopy/energy dispersive X-ray spectroscopy mapping, and laser scanning microscopy. The MF-aligned QPVA/GO-Fe3O4 electrolyte possessed higher conductivity and lower permeability than the un-aligned QPVA/GO-Fe3O4 membrane and pristine QPVA film. The aligned QPVA/GO-Fe3O4 composite exhibited a peak power density of 172.4 mW cm−2 at 60 °C, which is higher than those of the composite without the MF treatment (67.7 mW cm−2) and the pristine QPVA (50.3 mW cm−2). This research demonstrates the extraordinary benefits of MF assisted GO-Fe3O4 nanofillers in facilitating the ion conduction and barrier property of a polymeric composite at 0.1% filler loading.

Optimal loading of quaternized chitosan nanofillers in functionalized polyvinyl alcohol polymer membrane for effective hydroxide ion conduction and suppressed alcohol transport

A polymer composite was prepared by incorporating 5-20 wt% quaternized chitosan (Q-chitosan) nanoparticles into quaternized polyvinyl alcohol (Q-PVA) to enhance the dimensional stability and conductive properties. Compared with the pristine Q-PVA membrane, the ionic conductivity of the Q-PVA composites with 5–10 wt% Q-chitosan was improved due to increased polymeric free volume hole density. The methanol permeability is suppressed in these Q-PVA/Q-chitosan composites because of the confined swelling in the presence of the fillers, shrinking the free volume size. The Q-PVA/5%Q-chitosan composite exhibits higher peak power density (Pmax) than other Q-PVA membranes in direct methanol fuel cells. A Pmax of 92 mW cm−2 is attained using the Q-PVA/5%Q-chitosan composite at 90 °C with 5–6 mg cm−2 catalyst loads on micro-porous layer-containing carbon cloth. The high load of 20 wt% Q-chitosan does not benefit ionic conduction and power generation, probably due to interfacial resistance at rough surfaces. Using the Q-PVA/5%Q-chitosan composite and reduced catalyst loads of 1–2 mg cm−2 on pristine carbon cloth, Pmax of 90 mW cm−2 can be achieved at 60 °C for both methanol and ethanol fuel cells, but declined at 90 °C due to insufficient catalysts. Overall the Q-PVA/Q-chitosan composite offers a potential electrolyte for energy devices operating in an alkaline environment.

Gradiently distributed iron oxide@graphene oxide nanofillers in quaternized polyvinyl alcohol composite to enhance alkaline fuel cell power density

The magnetite nanoparticles on graphene oxide (Fe3O4@GO) nanofiller are synthesized, and incorporated in a polymeric matrix to produce effective electrolyte membrane for direct alkaline methanol/ethanol fuel cells. Fe3O4@GO nanofillers (0.1%) are gradiently distributed along the through-plane direction in a quaternized poly(vinyl alcohol) (QPVA) membrane by applying an external magnetic field (MF) during the film drying step. The present study is the first work to illustrate a facile method to form gradient distribution of nanofillers in a QPVA matrix via applying MF, resulting in a polymer-rich region in the center and a nanofiller-rich region near the membrane surface. This MF assisted QPVA/0.1%Fe3O4@GO nanocomposite membrane exhibits decreased dimensional changes without sacrificing the potassium hydroxide (KOH) doping level compared to QPVA. This nanocomposite membrane design not only reduces the permeability but also improves the ionic conductivity. Maximum power densities of 200 and 144.3mWcm−2 are achieved when the fuel cell is fed with 2M methanol or 3M ethanol at 60°C using the magnetic-field assisted nanocomposite electrolyte. The fabrication of high-performance nanocomposite membrane electrolytes using a MF implies promising potential and an innovative future trend for fuel cells.

Reorientation of Magnetic Graphene Oxide Nanosheets in Crosslinked Quaternized Polyvinyl Alcohol as Effective Solid Electrolyte

This work aims to clarify the effect of magnetic graphene oxide (GO) reorientation in a polymer matrix on the ionic conduction and methanol barrier properties of nanocomposite membrane electrolytes. Magnetic iron oxide (Fe3O4) nanoparticles were prepared and dispersed on GO nanosheets (GO-Fe3O4). The magnetic GO-Fe3O4 was imbedded into a quaternized polyvinyl alcohol (QPVA) matrix and crosslinked (CL-) with glutaraldehyde (GA) to obtain a polymeric nanocomposite. A magnetic field was applied in the through-plane direction during the drying and film formation steps. The CL-QPVA/GO-Fe3O4 nanocomposite membranes were doped with an alkali to obtain hydroxide-conducting electrolytes for direct methanol alkaline fuel cell (DMAFC) applications. The magnetic field-reoriented CL-QPVA/GO-Fe3O4 electrolyte demonstrated higher conductivity and lower methanol permeability than the unoriented CL-QPVA/GO-Fe3O4 membrane or the CL-QPVA film. The reoriented CL-QPVA/GO-Fe3O4 nanocomposite was used as the electrolyte in a DMAFC and resulted in a maximum power density of 55.4 mW·cm−2 at 60 °C, which is 73.7% higher than that of the composite without the magnetic field treatment (31.9 mW·cm−2). In contrast, the DMAFC using the CL-QPVA electrolyte generated only 22.4 mW·cm−2. This research proved the surprising benefits of magnetic-field-assisted orientation of GO-Fe3O4 in facilitating the ion conduction of a polymeric electrolyte.

Mechanical Properties and Thermal Resistance of Natural Rubber Nanocomposite Reinforced with Quaternized Polyvinyl Alcohol/Silica Nanoclusters

Quaternized polyvinyl alcohol (QPVA) was synthesized and used as an intermedium to improve dispersion of silica (SiO2) in natural rubber (NR). QPVA/SiO2 nanoclusters reinforced NR nanocomposite was prepared by latex compounding via electrostatic interaction. TEM micrographs demonstrated QPVA/SiO2 nanoclusters were distributed around NR particles, forming shell-core structure. The mechanical properties and thermal ageing resistance of NR-QPVA/SiO2 were significantly improved compared with that of neat NR. The tensile strength of NR-QPVA/SiO2 film was improved by 60%, when the SiO2 content is 3%. SEM pictures indicated SiO2 was homogenous dispersed throughout NR matrix in the presence of QPVA. It also demonstrated that SiO2 could enhance thermal stability of NR, as NR-QPVA/SiO2 had best surface morphology after 72 hours thermal ageing at 100 °C. The thermal decomposition temperature and glass transition temperature of NR-QPVA/SiO2 film increased to a higher temperature due to strong polymer–filler interaction, which also indicated that all the ingredients were compatible and homogenous.

Highly conductive quasi-coaxial electrospun quaternized polyvinyl alcohol nanofibers and composite as high-performance solid electrolytes

Electrospun quaternized polyvinyl alcohol (Q-PVA) nanofibers are prepared, and a potassium hydroxide (KOH)-doped nanofiber mat demonstrates enhanced ionic conductivity compared with a dense Q-PVA film with KOH doping. The Q-PVA composite containing 5.98% electrospun Q-PVA nanofibers exhibits suppressed methanol permeability. Both the high conductivity and suppressed methanol permeability are attributed to the quasi-coaxial structure of the electrospun nanofibers. The core of the fibers exhibits a more amorphous region that forms highly conductive paths, while the outer shell of the nanofibers contains more polymer crystals that serve as a hard sheath surrounding the soft core. This shell induces mass transfer resistance and creates a tortuous fuel pathway that suppresses methanol permeation. Such a Q-PVA composite is an effective solid electrolyte that makes the use of alkaline fuel cells viable. In a direct methanol alkaline fuel cell operated at 60 °C, a peak power density of 54 mW cm−2 is obtained using the electrospun Q-PVA composite, a 36.4% increase compared with a cell employing a pristine Q-PVA film. These results demonstrate that highly conductive coaxial electrospun nanofibers can be prepared through a single-opening spinneret and provide a possible approach for high-performance electrolyte fabrication.

Development and characterization of quaternized poly (vinyl alcohol) composite nanofiltration membranes

A novel positively charged composite nanofiltration (NF) membrane was developed and fabricated with cross-linked quaternized polyvinyl alcohol (q-PVA) as the active layer and polysulfone (PS) as the base support. The crosslinking was achieved by reacting q-PVA with 1,6-hexamethylene diisocyanate (HDI) at ambient temperature. Rejection performance of q-PVA composite NF membrane was measured as functions of quaternization degree (QD), q-PVA concentration, and the addition of low-molecular-weight inorganic electrolyte. It was found that the rejection of q-PVA/PS composite NF membrane for both inorganic electrolytes of MgCl2 and Na2SO4 increased with increasing QD. The q-PVA membrane showed 89.2 % of rejection and 10.3 kg m−2 h−1 of permeate flux to 5 mM MgCl2 solution at q-PVA concentration of 2.0 wt%. The rejections of q-PVA membrane for inorganic electrolytes followed the order: CaCl2 > MgCl2 > MgSO4 > NaCl > Na2SO4, agreeing well with Donnan exclusion theory.

Novel quaternized polyvinyl alcohol/quaternized chitosan nano-composite as an effective hydroxide-conducting electrolyte

A novel polymer composite electrolyte consisting of quaternized polyvinyl alcohol (Q-PVA) and quaternized chitosan nano-particles (Q-chitosan) is synthesized for use in a direct alcohol alkaline fuel cell (DAAFC). The quaternization efficiencies of PVA and chitosan particles are 2.6% and 39%, respectively. Incorporation of 5% Q-chitosan nano-particles into the Q-PVA matrix results not only in an increased ion-exchange capacity but also a decreased polymer crystallinity and higher free volume hole density, which significantly enhance ion conduction. The shrunk polymer free volume size suppresses methanol permeability in the Q-PVA/Q-chitosan composite. In addition, the resulting nano-composite exhibited an inhibited in-plane swelling ratio without sacrificing the alkali uptake level. The KOH-doped Q-PVA/Q-chitosan was resistant to the Fenton reagent. In DAAFCs, a maximum power density of 73mWcm–2 is achieved using the Q-PVA/5%Q-chitosan electrolyte when fed with 2M methanol at 60°C or 59mWcm–2 with 3M ethanol at 60°C. The resulting maximum power densities are higher than most literature data. The alkaline fuel cell demonstrated stable long-term power output for at least 230h. This result confirms that the Q-PVA/Q-chitosan electrolyte exhibits great potential for future commercialization.

On-site crosslinked quaternized poly(vinyl alcohol) as ionomer binder for solid alkaline fuel cells

Water-soluble polyvinyl alcohol functionalized with quaternary ammonium groups and crosslinked quaternized polyvinyl alcohol were synthesized and used to prepare an ionomer binder solution having a low boiling point and high dielectric constant solvent to be used in electrodes for solid alkaline fuel cells. The polyvinyl alcohol was quaternized to have anion-conducting ability using glycidyltrimethylammonium chloride. To prevent washing-out of the water-soluble anion-conducting ionomer during fuel cell operations, the quaternized poly(vinyl alcohol) was successfully crosslinked by using an on-site crosslinking method. The highest ionic conductivity of the ionomer was 2.3 × 10−2 S cm−1, and its ion exchange capacity was 1.2 meq g−1 at room temperature. The electrodes were fabricated by a spray method on anion-exchangeable membranes, and membrane-electrode assemblies were operated at 50 °C in ambient pressure and were characterized by voltage–current relationship and cyclic voltammetry. The highest performance of the membrane-electrode assemblies having the electrode with the ionomer of 25 wt.% in dry weight basis was 172.8 mW cm−2 at 0.485 V. As a result, the anionic binder electrodes introduced by the on-site crosslinking were successfully functioned both to conduct OH− ions between electrodes and an electrolyte and to move electron to an external circuit by forming three phase boundary at the electrode of the membrane-electrode assemblies.