Showing papers in "Reactive & Functional Polymers in 2020"
TL;DR: This review describes the choices of support materials and cross-linkers together with several mechanisms that influence the performance, stabilization and hyperactivation of immobilized enzymes.
Abstract: The primary means of immobilizing enzymes are to boost the enzyme productivity and operational stability, alongside facilitating the reuse of enzymes. Notwithstanding the aforementioned benefits, enzyme immobilization promotes high catalytic activity and stability, convenient handling of enzymes, in addition to their facile separation from reaction mixtures without contaminating the products. This review describes the choices of support materials and cross-linkers together with several mechanisms that influence the performance, stabilization and hyperactivation of immobilized enzymes. Altering enzyme properties often changes the enzyme structure due to random modifications in the behavior, which in some cases can be positive or negative. Future strategy to develop new generations of immobilized enzymes should capitalize on the rapid advances of genetic manipulation, organic chemistry, computational chemistry and bioinformatics, reactor and reaction design. Upcoming efforts to improve enzymes as industrial biocatalysts must consider their development for increased selective promiscuity suitable for multiple biotransformations, either independently or as catalytic cascade processes thereby enhance the cost-effectiveness of the processes.
137 citations
TL;DR: The drug delivery systems constructed by representative natural polymers, polysaccharides and proteins, including chitosan and hyaluronic acid, and proteins (silk fibroin and collagen), are generally summarized.
Abstract: Natural polymers have been extensively explored as the vehicles for encapsulation and delivery of drugs and other bioactive molecules, which have attracted tremendous attention. Their inherent advantages in marvelous biocompatibility, controlled enzyme degradation, specific interactions with some biomolecules, and easy modification endow them with versatility in drug delivery. In this perspective, the drug delivery systems (DDS) constructed by representative natural polymers, polysaccharides (chitosan and hyaluronic acid) and proteins (silk fibroin and collagen), are generally summarized. Payloads mainly involve small molecular weight drug, proteins, and DNA for the applications of tissue engineering, wound healing or anticancer therapy. Moreover, the DDS constructed by their derivatives and with other materials also have been presented focusing on the chemical and morphological modifications, the addtions of smart stimuli-triggered or targeted motifs and so on, which evidently promoted the delivery and therapy efficiency. Obviously, more intelligent and specific delivery strategies will be developed and more multifunctional natural polymers based carriers will be expended in the future. We try to seek more insights into the evolution of delivery system so as to figure out what we will truly gain in the next few decades to come.
135 citations
TL;DR: A comprehensive and updated overview of the state of the art related to the biomedical applications of nanoparticles coated with chitosan can be found in this article, where the methodological aspects of the coating process, which is performed by the addition of a chitoshan solution into previously prepared nanoparticles or during nanoparticle formation, was reviewed, as well as the techniques employed to confirm an efficient coating process.
Abstract: This review provides a comprehensive and updated overview of the state of the art related to the biomedical applications of nanoparticles coated with chitosan. Discussions were based on selected literature in the field. Here, we discussed nanoparticles constituted by polymer, lipid and metal materials, which have been coated with chitosan. In addition, the methodological aspects of the coating process, which is performed by the addition of a chitosan solution into previously prepared nanoparticles or during nanoparticle formation, was reviewed, as well as the techniques employed to confirm an efficient coating process, such as determinations of particle size and zeta potential. Special attention is given to physicochemical and biological advantages brought by the chitosan-coating, such as increase in physicochemical stability, controlled release, improvement of tissue/cells interaction, and increase in the bioavailability of drugs (or active substances) and drug efficacy. We also pointed out safety concerns regarding chitosan-coated nanoparticles based on the results presented so far in the literature.
118 citations
TL;DR: In this paper, the authors present a comprehensive collection of published reports on anticorrosive effects of pure and cured epoxy resins for different metals and alloys in different electrolytes.
Abstract: Epoxy resins (ERs) represent a special class of organic macromolecules that are comprehensively used for different industrial applications. Because of their macromolecular nature, ERs provide better surface coverage and anticorrosive activities than simple organic corrosion inhibitors. The peripheral polar functional groups of ERs act as adsorption centers during metal-inhibitor interactions. Several ERs in pure and cured forms had been used as anti-corrosive coating materials, especially for carbon steel in acidic and sodium chloride (3% and 3.5%) solutions. Most ERs act as interface and mixed-type corrosion inhibitors. Numerous computational simulations had been used to demonstrate the anticorrosive effects and adsorption behavior of ERs on metallic surfaces. However, most ERs have limited solubility; therefore they are better applied as coating materials for anticorrosive purposes. Literature survey showed that numerous ER-based coatings are developed and successfully employed for carbon steel and aluminum in brine solution. The anticorrosive effect of ER coatings can be further enhanced by adding organic and inorganic additives. The additives block the surface micropores present in ER coatings through which corrosive species can penetrate or diffuse and rapture the coating structures. This review article serves as a comprehensive collection of published reports on anticorrosive effects of pure and cured ERs for different metals and alloys in different electrolytes.
113 citations
TL;DR: In this paper, the authors present an overview on the most recently published information on the preparation of porous chitosan (CS) based composite hydrogels, such as: porous polygonal beads and monoliths, porous CS/inorganic particles, porous semi-and full-IPN hydrogel, and their applications either as very efficient composite sorbents for heavy metals and dyes, or as hemostats, smart drug delivery systems, wound dressings.
Abstract: Chitosan (CS) as the only polycation coming from renewable resources is endowed with intrinsic valuable properties, such as: biocompatibility, biodegradability, low cost, easy availability, and high reactivity due to plenty of the reactive functional groups (-NH2 and –OH). Therefore, CS and its derivatives have been involved in numerous applications, either alone or as components in composite materials. This review aims to present an overview on the most recently published information on the preparation of porous CS based composite hydrogels such as: porous chitosan/synthetic polymer as beads and monoliths, CS/inorganic particles, porous semi- and full-IPN hydrogels, and on their applications either as very efficient composite sorbents for heavy metals and dyes, or as hemostats, smart drug delivery systems, wound dressings. The techniques currently applied to prepare porous CS-based composites, including ice-templating (cryogelation), freeze-thawing, freeze-drying (lyophilization), and imprinting/leaching will be especially highlighted. Using cryogelation in tandem with IPN strategy led to composite cryogels with high mechanical properties and high performances in separation processes of ionic species. Main factors which control the separations of dyes and heavy metal ions by porous CS-based composite sorbents are discussed based on the recently published articles and own results.
107 citations
TL;DR: In this paper, a Cr(VI)-imprinted-poly(4-VP-co-EGDMA) (IIP) was proposed to be used in the process of selective extraction of low concentration of Cr (VI) ion from aqueous solution.
Abstract: A Cr(VI)-imprinted-poly(4-VP-co-EGDMA) (IIP) was proposed to be used in the process of selective extraction of low concentration of Cr(VI) ion from aqueous solution. The polymer was synthesized by using Cr(VI) ion as a template, 4-vinylphiridine (4-VP) as complexion agent and monomer, ethylene glycol dimethyl acrylate (EGDMA) as cross-linker, benzoyl peroxide (BPO) as initiator and ethanol/acetone as a porogen. Non ion-imprinted-poly(4-VP-co-EGDMA) (NIP) as a control polymer was prepared too. The synthesis was conducted by using precipitation polymerization method. The prepared of IIP unleached, IIP leached and NIP were characterized by XRD, FTIR, SEM-EDX and BET-BJH instrument. Based on the characterization data, it can be found that all of this imprinting material have a micro and mesopore structures. The effect of sorbent dosage, pH, contact time and temperature on Cr(VI) adsorption from aqueous solution were investigated. The result shows that the adsorption of Cr(VI) ion was highest at pH 2 with 30 min contact time at 313 K with an initial concentration of Cr(VI) 14 mg/L. The selective studies shows that the IIP material was a very selective to adsorp Cr(VI) even in water was found interfering ion such as Ni(II) and Cr(III) respectively. Kinetic and isotherm modeling were also studied by using 5 models in each. The result of modeling kinetic shows that Cr(VI) adsorption fit with the Pseudo-second-order model while modeling isotherm followed the Freundlich model. The application of this material to adsorb Cr(VI) from electroplating industrial waste which reaches 96% and the reusability testing also shows that this adsorbent has good stability even though it was used 10 times repeatedly.
93 citations
TL;DR: In this article, an overview of current understanding in the areas of issues caused by migration of plasticizers from flexible PVC products and the current bans in dealing with these issues are comprehensibly reviewed.
Abstract: Poly (vinyl chloride)(PVC), as the second general plastic just following the product of polyethylene (PE), has been widely applied in building, electrical parts, automobile, package and other fields of our common life. PVC products have accounted for about 80% of all plasticizers consumed. Phthalates, as the mostly used plasticizers, have gradually been restricted because of their migration and reproductive toxicity. This paper is an overview of current understanding in the areas of issues caused by migration of plasticizers from flexible PVC products and the current bans in dealing with these issues. The countermeasures and the recent scientific strategies to prevent plasticizer migration from PVC materials are comprehensibly reviewed. The advantages and disadvantages of various strategies are compared to conduct more in-depth research and find more scientific and effective solutions.
70 citations
TL;DR: In this paper, the use of functional polymers for the sorption of metallic species in water was widely practiced in treatment processes and the main parameters that had to be considered when choosing functional organic sorbents for the removal of metallic pollution were highlighted.
Abstract: The use of functional polymers for the sorption of metallic species in water was widely practiced in treatment processes. Such sorbents offered the possibility to remove a large range of metals because of the variety of possible functional groups on polymeric backbones. In particular, acidic groups (carboxylic, phosphonic or sulfonic groups) proved to be of great interest for the sorption of different cations. Sorption efficiency and selectivity through complexation or ion exchange interactions were directly linked to the nature of both the functional groups and the cationic metallic ions. In addition, the physical nature of materials was another important parameter that had to be considered. Depending on the polymer solubility, the cross-linking density, and the polymeric architecture, significant differences regarding sorption properties were observed in the sorption kinetics. Thus, it was challenging to select the appropriate polymeric sorbent with the most relevant physical nature and functionality in the area of wastewater treatment. This review aims at reporting organic polymeric materials bearing acidic groups able to interact (selectively or not) with metallic cations. Both synthetic and bio-based materials were reviewed and main parameters that had to be considered when choosing functional organic sorbents for the removal of metallic pollution were highlighted. Finally, recyclability of the polymeric sorbents was also considered.
62 citations
TL;DR: In this paper, a novel thin-film nanocomposite forward osmosis (TFN-FO) membrane and its structural properties and performance was further assessed in synthetic and industrial wastewater samples.
Abstract: This study presents the synthesis of a novel thin-film nanocomposite forward osmosis (TFN-FO) membrane and its structural properties and performance; heavy metals removal behavior was further assessed in synthetic and industrial wastewater samples. The novel lab-fabricated TFN-FO membranes included a support layer (SL) constructed by the incorporation of different concentrations (0–8 wt%) of polyethylene glycol 400, polysulfone, and 1-methyl, 2-pyrrolidone via the phase inversion process and an active layer (AL) formed through incorporating different weight ratios (0–0.012 wt%) of graphene oxide (GO), 1, 3-Phenylenediamine and 1, 3, 5-benzene trichloride into the polyamide layer via the interfacial polymerization reaction. Compared with traditional TFC membranes, the TFN-FO membranes exhibited higher hydrophilicity, porosity, water permeability, water flux and salt rejection and lower reverse salt flux, specific reverse salt flux and internal concentration polarization (ICP). The water flux in the TFN membrane (34.3 LMH) increased by 174% and 129%, compared to the TFC membrane (12.5 LMH) and commercial FO membrane (15 LMH), respectively. The rejection rates of TFN FO membranes regarding Pb, Cd, and Cr were 99.9, 99.7 and 98.3%, respectively. The breakthrough time of heavy metals exceeded 14.5 h and 96% concerning flux recovery ratio. The modified FO membranes revealed excellent improvement in membrane structure, FO performances and separation properties.
57 citations
TL;DR: Chitosan/MCM-48 composites were synthesized as promising and eco-friendly bio-adsorbents for Cd2+ ions from water as mentioned in this paper, which showed novel porous structures and complex functional groups making them of high adsorption capacities.
Abstract: Chitosan/MCM-48 (CH/MCM) and β-cyclodextrin/MCM-48 (CD/MCM) composites were synthesized as promising and eco-friendly bio-adsorbents for Cd2+ ions from water. The composites showed novel porous structures and complex functional groups making them of high adsorption capacities. The adsorption behaviors of CH/MCM and CD/MCM are highly controlled by the tested pH values realizing their best capacities at pH 7. The kinetic evaluation indicated the excellent agreement between the uptake of Cd2+ by CH/MCM and CD/MCM with the pseudo-first-order model achieving equilibrium intervals of 480 min and 600 min, respectively. Based on the values of Chi-squared (X2) and the correlation coefficient, the composites displayed adsorption properties related to the Freundlich hypothesis with a multilayer form. Additionally, the Gaussian energies of them are 2.23 KJ/mol (CH/MCM) and 2.46 KJ/mol (CD/MCM) reflecting physical uptake of Cd2+ by the studied composites. The thermodynamic investigation implied spontaneous uptake of Cd2+ by the composites with endothermic reactions. The prepared CH/MCM and CD/MCM are of 122.4 mg/g and 152.2 mg/g theoretical qmax, respectively which are higher values than the reported results for several studied adsorbents. Moreover, the synthetic CH/MCM and CD/MCM showed high reusability as adsorbents for Cd2+ to be applied effectively six times.
56 citations
TL;DR: Aminobenzothiazole-substituted cyclotriphosphazene derivative (ABCP) was successfully synthesized and used as reactive flame retardant to improve the fire safety of epoxy resin (EP) as discussed by the authors.
Abstract: Aminobenzothiazole-substituted cyclotriphosphazene derivative (ABCP) was successfully synthesized and used as reactive flame retardant to improve the fire safety of epoxy resin (EP). The chemical structure of ABCP was confirmed by Fourier transform infrared spectroscopy (FTIR), 1H and 31P nuclear magnetic resonance (NMR), high-resolution mass spectroscopy (HR-MS) and elemental analysis (EA). The curing behavior, thermal stability, thermo-mechanical property and flame retardancy of the prepared EP systems were studied. The differential scanning calorimeter (DSC) results indicated that ABCP induced the anionic polymerization of EP and facilitated the addition reaction between EP and 4,4′-diamino-diphenyl sulfone (DDS). The thermogravimetric analysis (TGA) results indicated that ABCP accelerated the thermal degradation of EP matrix and contributed to the formation of more residual chars with better thermo-oxidative stability. The dynamic mechanical analysis (DMA) results indicated that EP/DDS/ABCP thermosets exhibited higher storage modulus at 50 °C and their glass transition temperature (Tg) values were slightly reduced by 6–10 °C, in comparison with EP/DDS thermoset. The combustion test results revealed the fire hazards of EP/DDS/ABCP thermosets were effectively reduced. Compared with EP/DDS thermoset, the limiting oxygen index (LOI) value of EP/DDS/ABCP-1.2 thermoset was increased to 31.2% and the sample passed UL94 V-0 rating; the average of heat release rate (av-HRR), peak of heat release rate (pk-HRR) and total heat release (THR) values of EP/DDS/ABCP-1.2 thermoset were reduced by 36.5%, 53.7% and 34.5%, respectively; particularly, the fire growth rate (FIGRA) of EP/DDS/ABCP-0.6 thermoset was reduced by half. The research on flame retardant mechanism disclosed that ABCP played dominated flame retardant effect in condensed phase.
TL;DR: In this article, the authors discuss the recent advances in chitosan-based hydrogels while highlighting its evolution from covalently crosslinked systems to ionotropically cross-linked super-absorbents.
Abstract: Among the various physical forms of chitosan, viz. films, fibres, nanoparticles, gels, sponges, solution, etc., gels hold the most commercial importance. They are widely used in many areas, ranging from biomedicine to agriculture. This review discusses the recent advances in the chitosan-based hydrogels while highlighting its evolution from covalently crosslinked systems to ionotropically crosslinked super-absorbents. Distinctions into first, second and third generations of chitosan-based hydrogels are drawn based on the nature of crosslinks, environmental stability, mechanical strength and toxicity. While the first generation comprises chemically and metal-coordination crosslinked hydrogels, which were among the earliest to be identified, the second generation comprises of those physically crosslinked. Although the latter lack strength and stability, they are biocompatible in nature. The third generation, on the other hand, comprises of dense physical crosslinks that contribute to the strength and stability, without compromising on the biocompatibility.
TL;DR: In this article, the hydrophilic organic films were successfully coated on g-C3N4 nanosheets through facile co-modification of dopamine (DA) and silane coupling agent (KH560).
Abstract: In this work, the hydrophilic organic films were successfully coated on g-C3N4 nanosheets through facile co-modification of dopamine (DA) and silane coupling agent (KH560). The co-modification of polydopamine (PDA) and KH560 on lamellar g-C3N4 greatly enhanced dispersion of g-C3N4 in aqueous solution and dramatically improved the compatibility and interfacial interaction with waterborne epoxy. The effect of incorporating modified g-C3N4 nanosheets into waterborne epoxy on anticorrosion performance for P110 steel substrates were demonstrated through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and salt spray test. The results revealed that the |Z|0.01Hz value and percentage coating resistance (Rc) gain (ηc%) of nanocomposite coating increased by 977% and 90.72% with the addition of modified g-C3N4 nanosheets in comparison with pure waterborne epoxy coating, exhibiting outstanding anticorrosion abilities. The reinforced anticorrosion performances of nanocomposite coating could be attributed to the notable shielding effect and well dispersibility of modified g-C3N4 nanosheets.
TL;DR: In this article, sulfonated chitosan (S-CS) was prepared by hydrothermal grafting reaction using 4-formyl-1,3-benzene disulfonate and glutaraldehyde as a cross-linker reagent.
Abstract: In this research, sulfonated chitosan (S-CS) was prepared by hydrothermal grafting reaction using 4-formyl-1,3-benzene disulfonate and glutaraldehyde as a cross-linker reagent. Batch adsorption experiments were performed to demonstrate the adsorptive properties of S-CS with a cationic dye (methylene blue; MB) as a model organic pollutant. The effect of the solution pH (3−12), initial dye concentration (50–200 mg L−1), contact time (0–24 h) and temperature (30–50 °C) on the relative removal of MB were studied. The kinetics of adsorption for MB showed a good correlation with the pseudo-second order kinetic model, while the adsorption isotherm at equilibrium was conformed to the Temkin model (R2 > 0.99). The maximum adsorption capacity, qm was 351.7, 326.1 and 302.4 mg g−1 at 303, 313 and 323 K, respectively. Owing to the simpler preparation method, relatively high adsorption capacity and regeneration ability, S-CS represents a promising adsorbent for the controlled MB removal and for other related organic dye pollutants from aqueous solution.
TL;DR: In this article, two functionalized chitosan nanocomposities, (CTS-Cin) and (Fe3O4@CTS)-Cin, were synthesized and explored for the removal of toxic chromium from aqueous solution.
Abstract: Starting from the biopolymer chitosan, two new functionalized chitosan nanocomposities, (CTS-Cin) and (Fe3O4@CTS-Cin) were synthesised and explored for the removal of toxic chromium from aqueous solution. The two chitosan based adsorbents were prepared by co-precipitation method under N2 conditions and fully characterized by means of different analytical techniques, FT-IR, EDS, XRD, SEM, HR-TEM and VSM. Adsorption mechanism of toxic Cr (VI) was performed by batch experiments as a function of pH, adsorbent dosage, contact time and initial hexavalent chromium concentration. The adsorption isotherm and kinetics were fitted well by Langmuir and pseudo-second–order model indicating that the adsorption process is monolayer adsorption. The maximum adsorption capacity for CTS-Cin adsorbent at 298 K is 61.35 mg/g at pH = 2 and it achieved adsorption equilibrium within 35 min. However, Fe3O4@CTS-Cin adsorbent achieved adsorption equilibrium within 80 min and its maximum adsorption capacity is 58.14 mg/g at pH = 3. These results indicate that the two modified adsorbents represent promising adsorbents that would have a practical impact on wastewater treatment applications.
TL;DR: In this paper, an ion-imprinted sorbent (Ni-CDMO) derived from diacetylmonoxime (DMO)-chitosan Schiff base has been prepared by incorporating Ni(II) ion matching sites, which can selectively coordinate and recover Ni (II) ions from aquatic media.
Abstract: An ion-imprinted sorbent (Ni-CDMO) derived from diacetylmonoxime (DMO)-chitosan Schiff base has been prepared by incorporating Ni(II) ion matching sites, which can selectively coordinate and recover Ni(II) ions from aquatic media. The chitosan was first modified by DMO to improve the targeted Ni(II) ion coordination and then the polymeric Ni-complex was treated with glyoxal to cross-link the polysaccharide chains and maintain the coordination sites rigid and inflexible after eluting the Ni(II) ions from the sorbent matrix. The maximum Ni(II) ion capacities of the Ni-CDMO and the control adsorbent C-CDMO were determined by performing the isotherm studies under different Ni(II) initial concentrations and treating the obtained experimental results using Langmuir and Freundlich models. The maximum capacity was around 135 mg/g, which is considered a high competing value. Furthermore, the competitive extraction of Ni(II) ions among various similar ions including Pb(II), Cu(II), Co(II), and Cd(II) was carried out using Ni-CDMO and C-CDMO and the results confirmed the distinct role of the utilized imprinting procedure in creating a considerable Ni(II) ion selectivity within the structure of the Ni-CDMO. Also, the regeneration and reusability experiments indicated the preservation of approximately 98% of the initial efficiency after the performance of five consecutive cycles.
TL;DR: In this article, a highly porous functional hydrogel from the egg white (EW) integrated with polyethyleneimine (PEI) was prepared and examined for the adsorptive removal of the Cu2+, Pb2+ and Cd2+ ions in aqueous solutions.
Abstract: The water pollution caused by the heavy metal ions have raised potent damages to the water ecosystem and human health. It is thus important to develop materials that can capture the heavy metal ions effectively and efficiently in the wastewater to resolve this issue. Herein, a highly porous functional hydrogel from the egg white (EW) integrated with polyethyleneimine (PEI) was prepared and examined for the adsorptive removal of the Cu2+, Pb2+ and Cd2+ ions in aqueous solutions. A systematic study was performed to illustrate the EW/PEI hydrogel's excellent affinity to the metallic ions in both the mono- and competitive adsorption systems. The maximum adsorption capacities for the Cu2+, Pb2+ and Cd2+ ions in the mono-adsorption system were determined to be 7.494, 2.194 and 3.705 mmol g−1, respectively with the adsorption rates and isotherms complying with the pseudo-second order kinetics and Langmuir isotherm model, respectively. Furthermore, in situ reduction turned the adsorbed Cu2+ ions into uniformly distributed Cu nanoparticles (NPs) in the EW/PEI hydrogel. This material can serve as an excellent catalyst as confirmed by a ~98% conversion of 4-nitrophenol (20 mmol) to 4-aminophenol in 10 min at the ambient temperature. The EW/PEI hydrogel and the Cu NPs-decorated EW/PEI hydrogel catalyst can be regenerated easily as proved by the consecutive adsorption/desorption and catalysis experiments for several repetitions, respectively. Therefore, the current study highlights the application of the EW/PEI hydrogel as an effective and practical approach for capturing and recycling/utilizing the toxic metal ions in the wastewater.
TL;DR: In this article, the authors developed electrically conductive nanocomposites based on cellulose nanowhiskers via in situ emulsion polymerization reaction of pyrrole and in presence of silver nitrate (AgNO3) as an oxidative agent and surfactant.
Abstract: We developed novel electrically conductive nanocomposites based on cellulose nanowhiskers (CNW) via in situ emulsion polymerization reaction of pyrrole and in presence of silver nitrate (AgNO3) as an oxidative agent and surfactant. CNW were employed as carriers comprising high surface area-to-volume ratio and high porosity. Nickel(III) oxide (Ni2O3) nanoparticles were loaded onto the prepared composites using the sol-gel technique to provide nanocomposites of potentially excellent properties. Different nanocomposites were prepared including polypyrrole/silver NPs (PPy/AgNPs), cellulose nanowhiskers/polypyrrole/silver nanoparticles (CNW/PPy/AgNPs), and cellulose nanowhiskers/polypyrrole/silver nanoparticles/Ni(III) oxide nanoparticles (CNW/PPy/AgNPs-Ni2O3). The structural, morphological, thermal and dielectric properties of the prepared nanocomposites were studied by Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDX) and X-ray diffraction (XRD). The dielectric properties of the prepared nanocomposites, including dielectric constant e΄(ω), AC conductivity, tan δ, dielectric loss e˝(ω) and σac were explored. The incorporation of PPy onto CNW composites was found to increase the electrical conductivity from 2.5 × 10−11 to 1.1 × 10−7 S/cm. The AC conductivity was also found to increase upon increasing temperature demonstrating semiconducting activity.
TL;DR: In this article, the methylated β-cyclodextrin (M-β-CD), which was able to enhance the mechanical properties of WBPU and realize the synergistic effect between M − β-CD and UPy to raise the performance of self-healing, was introduced onto the main chain of the WBPU.
Abstract: Polymers which contain 2-Amino-4-hydroxy-6-methylpyrimidine (UPy) usually show good self-healing capabilities under certain conditions. In this study, the UPy was grafted into the side chain of waterborne polyurethane (WBPU), which was synthesized from 4,4-diisocyanate dicyclohexylmethane (H12MDI) and polycarbonate diol (PCDL), for giving the function of self-healing to the polymer. Meanwhile, the methylated β-cyclodextrin (M-β-CD), which was able to enhance the mechanical properties of WBPU and realize the synergistic effect between M-β-CD and UPy to raise the performance of self-healing, was introduced onto the main chain of WBPU. The Tg (glass transition temperature) of the polymer can be observed from dynamic mechanical property analysis (DMA) below room temperature, which facilitated the movement of the chain in self-healing process. From the tensile test, it showed that the cut polymer spline displayed a self-healing efficiency of 92.29% at 100 °C within 36 h. Furthermore, the disappearance of surface scratch of polymer film was observed by heating under a polarized microscope (POM) with a heating table. The results manifested that SWBPU exhibited great application as an intelligent response-type material.
TL;DR: In this article, the authors provide an overall investigation about the fabrication process of PPS ultrafine fiber including sea-island melt spinning, melt electrospinning and melt-blown spinning as well as the application of poly(phenylene sulfide) ultrafine fibers based materials like high temperature filter, lithium ion battery separator, high strength and high modulus composites, catalytic, adsorption, degradation membrane and so on.
Abstract: Poly (phenylene sulfide) ultrafine fiber is one kind of high-performance fiber with high specific surface area, corrosion resistance, chemical and thermal stability, which can be widely applied in various domains. However, there are few reports about the review of PPS ultrafine fiber. To meet this demand, the paper provides an overall investigation about the fabrication process of PPS ultrafine fiber including sea-island melt spinning, melt electrospinning and melt-blown spinning as well as the application of PPS ultrafine fiber based materials like high temperature filter, lithium ion battery separator, high strength and high modulus composites, oil/water separation membrane, catalytic, adsorption, degradation membrane and so on.
TL;DR: In this article, a poly(2-hydroxyethyl methacrylate-co-acrylamide)/polyvinyl alcohol/chitosan interpenetrating polymer network (IPN-CS) hydrogel films were fabricated by two-step free radical polymerization, aiming to enhance the tensile strength, water swelling and antibacterial activity.
Abstract: The novel poly(2-hydroxyethyl methacrylate-co-acrylamide)/polyvinyl alcohol/chitosan (P(HEMA-co-AM)/PVA/CS) interpenetrating polymer network (IPN-CS) hydrogel films were fabricated by two-step free radical polymerization, aiming to enhance the tensile strength, water swelling and antibacterial activity compared to P(HEMA-co-AM)/PVA hydrogel (IPN-0%CS). The different weight ratios of PVA and CS components were firstly crosslinked by glutaraldehyde. Then P(HEMA-co-AM) copolymers were interpenetrated into the primary networks of PVA/CS and crosslinked by ethylene glycol dimethacrylate to form the IPN-CS hydrogels. The functional group analysis confirmed that the IPN-CS hydrogels were successfully synthesized. The crystallinity, Tg and Tm, microporous and surface area of IPN-CS hydrogels tended to increase significantly with increasing CS content. The swelling equilibrium and surface area of IPN-CS hydrogel exhibited a linearly relationship with CS content. The swelling behavior of IPN-CS hydrogels was best described by the pseudo-first order kinetics and followed a non-Fickian diffusion mechanism. The IPN-5%CS hydrogel film exhibited the highest tensile strength (22.4 MPa) which was increased 2.7 folds of IPN-0%CS. All IPN-CS hydrogels demonstrated an excellent antibacterial activity against E. coli. These results suggest that the IPN-CS hydrogel films have promising potential used as wound dressings.
TL;DR: In this article, CMD-MNPs were synthesized with co-precipitation of ferrous and ferric ions, and different concentrations of CMD were applied into synthesis process.
Abstract: MNPs were synthesized with co-precipitation of ferrous and ferric ions. Carboxymethyl dextran (CMD) was covalently bound to MNPs and the influence of different concentrations on characteristics of CMD coated magnetic nanoparticles (CMD-MNPs) was studied. Different concentrations of CMD were applied into synthesis process. The surface morphology of CMD-MNPs was monitored by scanning and transmission electron microscopy, where their spherical shape was confirmed. Fourier transform infrared spectroscopy displayed characteristic bonds that confirmed the presence of CMD hydroxyl and carboxyl groups. Thermogravimetric analysis displayed a weight loss, which confirmed the coating weight of CMD. ζ-potential measurements revealed negatively charged hydroxyl groups of CMD, and polydispersity index (PdI) showed the most consistent sizes of CMD3-MNPs. Electron paramagnetic resonance and magnetization measurements confirmed a ferromagnetic system for all CMD-MNPs. Prepared CMD3-MNPs were used as carriers for immobilization of enzyme alcohol dehydrogenase (ADH). Immobilization was carried out at two different temperatures (20 °C and 4 °C) and thermal stability at 20 °C and 40 °C after 24 h was studied. Prepared CMD-MNPs exhibit a layer of CMD coating that provides proper magnetic and structural properties and can therefore be functionalized and used in bioactive compound immobilization, such as ADH.
TL;DR: In this article, a polyacrylamide grafted onto chitosan, cross-linked with N,N′-methylenebisacrylide, was synthesized by conventional (CM) and microwave assisted methods (MWM).
Abstract: Effective dye removal is of crucial importance for the well-being of the environment and human health, and hydrogels are top-players for this goal. In this work, hydrogels of polyacrylamide grafted onto chitosan, cross-linked with N,N′-methylenebisacrylamide, were synthesized by conventional (CM) and microwave-assisted methods (MWM). The products were characterized by Fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy and swelling capacity. The developed hydrogels were evaluated as an adsorbent for the azo dye Acid Blue 113. MWM provided higher yield of the product with reduced reaction time when compared to the CM. The dye removal efficiency by MWM was slightly lower than that observed by CM, but MWM showed a much higher maximum adsorption capacity than the conventional one. The adsorption behavior of conventional and MW hydrogels followed the Langmuir and Freundlich models, respectively. The MW hydrogel presented the best characteristics to be used as an adsorbent of the AB 113 dye.
TL;DR: In this article, cross-linked oxalic acid/chitosan hydrogels (ChOxb) were synthesized, characterized and tested for the adsorption of azo-dyes (Reactive Red 195 RR195) in contaminated wastewater; this novel biodegradable material was highly efficient.
Abstract: Cross-linked oxalic acid/chitosan hydrogels (ChOxb) were synthesized, characterized and tested for the adsorption of azo-dyes (Reactive Red 195 RR195) in contaminated wastewater; this novel biodegradable material was highly efficient. SEM-EDS and N2 adsorption/desorption were used to analyze specific area; FTIR-ATR spectra evidenced electrostatic interactions between protonated amino groups of chitosan and oxalate ions (intensity decrease and shift of amide-II band). Adsorption performance in batch assays showed a maximum percentage of removal of 90.6%, at pH = 4 (initial dye concentration of 300 mg.L−1). The maximum adsorption capacity (Qm) at pH = 4 was 110.7 mg.g−1, positioning ChOxb as one of the most efficient adsorption materials. Oxalic acid (natural organic acid) is an eco-friendly cross-linking agent that reduced swelling and improved chemical stability of ChOxb at low pH = 2.5. Redlich-Peterson adsorption isotherm presented the best fit; adsorption thermodynamic parameters were evaluated. Mixed surface reaction and diffusion-controlled kinetic model was the equation that best fitted kinetic data. FTIR-ATR, SEM-EDS and Z-potential showed electrostatic interactions between dye and amino groups of ChOxb; ChOxd can be reused without losing adsorption capacity and competitive electrostatic interactions between ChOxb-nitrate were observed. This new bio-material is an excellent alternative for the removal of RR195, improving Qm with better structural and functional properties.
TL;DR: Chitin and chitosan have great potential to be applied in industrial scale separation processes because they are natural, renewal biopolymers that have the added benefits of being nontoxic and mechanically and chemically stable as discussed by the authors.
Abstract: Chitin and chitosan have great potential to be applied in industrial scale separation processes because they are natural, renewal biopolymers that have the added benefits of being nontoxic and mechanically and chemically stable. They have been readily used in liquid chromatography as a stationary phase due to a variety of functional groups present in the unit of the polymer chain: an amine group at the C2 position, –CH3 moieties in the acetamido group at the C2 position, and –OH groups at the C3 and C6 positions. The biopolymers have been tested as a stationary phase for chromatographic separation of several compounds: metal cations, proteins, food compounds, drugs, or chiral mixtures. They have been used as a coating on silica or cellulose particles without any modification, or after modification with different substituents. The presented review outlines the state-of-the-art research pertaining to chitin and chitosan application in liquid chromatography.
TL;DR: In this paper, high-antibacterial electrospun cellulose acetate (CA) nanofiber mats with encapsulated lemon myrtle essential oil (LMEO) as a natural antibacterial agent were produced.
Abstract: Highly antibacterial electrospun cellulose acetate (CA) nanofiber mats with encapsulated lemon myrtle essential oil (LMEO) as a natural antibacterial agent were produced. The high antibacterial activity of LMEO was confirmed by minimum inhibitory concentration and the minimum bactericidal concentration analysis. Morphological, thermal, optical, chemical and antimicrobial properties of LMEO-loaded CA electrospun nanofibers were investigated. The morphology of the fiber mat was examined by SEM to study the effect of solvent type, solution viscosity, electrospinning voltage and incorporation of LMEO into the CA electrospun nanofibers. The average diameters of both CA and LMEO-loaded CA nanofibers were in the range of 440–515 nm. The electrospun nanofibers were of a white colour and low water activity. Thermogravimetric analysis indicated no change in degradation profile of CA, while differential scanning calorimetry indicated a lower degree of CA crystallinity upon incorporation of LMEO. The LMEO-loaded CA electrospun nanofibers eliminated Escherichia coli and Staphylococcus aureus by 100% even at the lowest loading concentration of LMEO of 2 wt%. The electrospun fiber mats, with moderate loading of LMEO, showed sustained release of LMEO over prolonged time and nanofibers retained their high antibacterial properties even after two months of storage. Therefore, these nanofibers could be promising candidates for active packaging or wound dressing applications with prolonged antimicrobial activity.
TL;DR: In this article, a new nanocomposite based on crosslinked Glycerol Dimethacrylate (GDMA) and the mesoporous silica MCM-41 was prepared.
Abstract: In this work, a new nanocomposite based on crosslinked Glycerol Dimethacrylate (GDMA) and the mesoporous silica MCM-41 was prepared. The GDMA is first synthesized by the ring opening of glycidyl methacrylate (GMA) using methacrylic anhydride (MA) and promoted by a new solvent-free green catalysis process at room temperature. The nanocomposites are further obtained by in-situ polymerization of the GDMA in the channels of the mesoporous silica and then tested for the removal of methylene blue (MB) dye. Effect of polymer content, adsorbent mass, contact time and initial dye concentration were studied and discussed in terms of affinity and adsorption efficiency. The results showed that the poly(GDMA) was well immobilized in the internal and external surface of the mesoporous silica MCM-41. The adsorption efficiency of MB dye increased with increasing poly(GDMA) content in which the nanocomposite (NC-3) exhibited the best adsorption capacity of MB dye. The adsorption of MB dye by nanocomposite NC-3 followed Langmuir adsorption isotherm models and pseudo-second-order kinetics. The maximum adsorbed amount of MB dye on nanocomposite NC-3 is 111.11 mg/g.
TL;DR: In this paper, the water treatment potential of chitosan-glucan nanopapers derived from common white-button mushroom (A. bisporus) extract as an adsorptive filter was investigated.
Abstract: Contaminated water represents a significant threat to public health, with heavy metals present in industrial effluents constituting a particular hazard. Conventional heavy metal removal processes are often expensive and rely on synthetic materials. Renewable adsorbents or filters, such as chitosan, provide a low-cost, simple alternative for treatment of water. Fungal chitin and hence fungal chitosan is a cheap, renewable, easily isolated, and abundant alternative to crustacean chitin. This study investigated the water treatment potential of chitosan-glucan nanopapers derived from common white-button mushroom (A. bisporus) extract as adsorptive filter. These nanopapers completely rejected 10 nm gold nanoparticles, indicating potential for virus filtration. They had copper ion (2 mM) adsorption capacities (up to 120 mg g−1) increasing with degree of deacetylation of fungal chitin on par with or even outperforming current chitosan membranes with the advantage of simpler production, not requiring further crosslinking. In order to improve the performance of fungal chitosan-glucan filters, hybrid filters with cellulose microfibres from fibre sludge were prepared. Hybrid nanopapers exhibited significantly increased copper ion adsorption (162 mg g−1) in conjunction with high water permeances (63,000 to 121,000 L h−1 m−2 MPa−1). The simple manufacturing process and impressive filtration/adsorbent properties of these renewable filters make them a viable option for water treatment helping to reduce the ecological impact of traditional water treatment processes.
TL;DR: A molecularly imprinted polymer layer coated on TiO2/CNDs/MIP as a novel nanocomposite was successfully synthesized by means of the surface imprinted technique using pendimethalin (PM) herbicide as the template molecule as discussed by the authors.
Abstract: A molecularly imprinted polymer layer coated on TiO2/carbon nanodots (TiO2/CNDs/MIP) as a novel nanocomposite was successfully synthesized by means of the surface molecularly imprinted technique using pendimethalin (PM) herbicide as the template molecule. O-phenylenediamine was used both as the functional monomer for MIP and as the precursor of carbon nanodots. The structure and properties of the nanoparticles and nanocomposites were characterized by FE-SEM, EDX, TEM, DLS, XRD, XPS, PL, FT-IR, BET, and UV–vis DRS. The photocatalytic activity, adsorption capacity, and adsorption selectivity of TiO2/CNDs/MIP and TiO2/CNDs/NIP were investigated. The results indicated that TiO2/CNDs/MIP nanocomposite exhibited the high adsorption capacity of 86.1 mg/g in 30 min and an excellent selectivity toward PM compared to other structural analogues due to the imprinted cavities and specific recognition sites on the surface of MIP. In addition, the TiO2/CNDs/MIP nanocomposite revealed the enhanced photodegradation efficiency (about 95%) of PM compared with TiO2, TiO2/CNDs, and TiO2/CNDs/NIP, as a result of its large adsorption capacity to template molecules and its narrow band gap energy under visible light. Using charge carrier scavengers, it was revealed that the O2 − radicals were the main surface species for the photodegradation of PM. Moreover, TiO2/CNDs/MIP nanocomposite exhibited reusability and high stability.
TL;DR: In this article, polyurethane modified cellulose acetate membrane provided enhanced separation with good antifouling property, which can be potentially used for the cleaning of the toxic metal-organic pollutants in wastewaters.
Abstract: The presence of both copper ion (Cu (II)) from industry and humic acid (HA) in natural waters may generate Cu (II)–HA complex, which is a non-biodegradable and toxic organic pollutant in the water. Removal of such toxic substance is of great importance and environmental significance. Although membrane technology provides a solution for the removal via the filtration, fouling still presents a major challenge for the effective separation. In this study, polyurethanes endcapped with β-cyclodextrin and lactic acid were synthesized and used as additives to be blended with cellulose acetate membranes, which possessed enhanced hydrophilicity, permeability and antifouling property for the removal of Cu (II) and HA. As an example, the polyurethane endcapped with lactic acid (LPU-CA) membrane exhibited high pure water flux (PWF) of 648 L m−2 h−1, as well as high flux recovery ratios (FRRs) of 97.8% and 92% and low irreversible fouling rate (Fir) of 2.2% and 7.8% for the ultrafiltration (UF) of HA and Cu (II)–HA complex, respectively, showing excellent anti-fouling performance. In addition, the Cu (II) and HA rejection was greatly enhanced by the HA enhanced complexation process. These results indicated that the polyurethanes modified cellulose acetate membrane provided enhanced separation with good antifouling property, which can be potentially used for the cleaning of the toxic metal-organic pollutants in wastewaters.