Showing papers in "Polymer Bulletin in 2018"

Synthesis, swelling and adsorption studies of a pH-responsive sodium alginate–poly(acrylic acid) superabsorbent hydrogel

Abstract: Polyacrylic acid grafted sodium alginate (SA-cl-PAA)-based hydrogel was synthesized by an aqueous polymerisation method An acrylic acid (AA) monomer was grafted onto sodium alginate (SA) using N,N′-methylene-bisacrylamide (MBA) and potassium persulfate (KPS) as a crosslinker–initiator system The impact of various parameters such as reaction time, the amount of solvent, pH, crosslinker amount, initiator concentration and monomer concentration on the swelling behavior of the synthesized hydrogel was investigated We obtained a hydrogel with swelling percentage 41,298% which is quite high Swelling studies were carried out under acidic (pH 2 buffer) and basic (pH 10 buffer) conditions and evaluated kinetically The results revealed that the swelling process follows second order kinetics, and the water transport inside the hydrogel supports a Fickian mechanism The swelling results also indicate that the swelling properties of the synthesized hydrogel showed an on- and off-switchable behavior under basic and acidic conditions, respectively The synthesized hydrogel was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) The hydrogel was used in the victoria blue R (VB) and rhodamine 6G (RG6) dye adsorption from wastewater It was found that hydrogel adsorbed 958 and 99% of VB and RG6 (132 ppm), respectively, within 77 min Adsorption of victoria blue is due to electrostatic interaction only, and removal of rhodamine 6G is explained on the basis of electrostatic interaction and hydrogen bonding

Preparation and characterization of polysulfone/graphene oxide nanocomposite membranes for the separation of methylene blue from water

Abstract: Composite membranes are known to be promising platform for treatment of water and wastewaters. The aim of this work was to produce an effective and versatile hazardous material separation platform, polysulfone/graphene oxide (PSf/GO) nanocomposite membranes with different ratios of GO. The nanocomposite membranes were prepared through phase inversion technique and characterized by Fourier transform infrared, Raman spectroscopy, X-ray diffraction, and scanning electron microscope. The results from the GO and PSf/GO analyses confirmed the formation of exfoliated GO nanosheets and relatively the homogeneous dispersion of GO in the PSf nanocomposite membranes. Addition of GO to the membrane matrix led to about 10° decrease in the contact angle, which nearly remained constant for all the composite membranes. The prepared membranes (i.e., PSf/GO and blank PSf membranes) were used for the separation of methylene blue from aqueous solution. In comparison with PSf membrane, PSf/GO membrane exhibited a remarkable adsorption/separation behavior.

Microwave-shielding behavior of silanized Cu and Cu–Fe 3 O 4 compound particle-reinforced epoxy resin composite in E-, F-, I-, and J-band frequencies

Abstract: In this work, microwave-shielding behavior of epoxy thermosetting plastic reinforced with silanized Cu and Cu–Fe3O4 compound particles were studied in frequency bands E, F, I, and J. The principal aim of this work is to evaluate the significant advantage of surface-modified magnetic and conductive fillers over as-received fillers in microwave shielding. The conductive and magnetic properties of epoxy resin were improved by additions of Cu and Fe3O4 particles. Compound particles of Cu–Fe3O4 were produced by mechanical alloying process (ball milling). The compound particles were surface treated by 3-Aminopropyltrimethoxysilane (APTMS) for better dispersion in epoxy resin matrix. Functional groups on particle’s surface after silane surface treatment were confirmed by FT-IR spectra analysis. The TEM images revealed that effective Cu–Fe3O4 particle compounding was formed at 1 h milling time. The maximum dielectric constant of 6.8 and magnetization of 675E−6 were observed for surface-modified compound particle-reinforced epoxy composite designation RCF2. Similarly, maximum microwave attenuation of 35% (44 dB) was observed for surface-modified compound particle-reinforced composite designation RCF2 in ‘J’-band frequency.

Blending modification of PBS/PLA and its enzymatic degradation

Abstract: This study used benzoyl peroxide (BPO) as a cross-linking agent to modify the blends of poly(butylene succinate) (PBS) and poly(lactic acid) (PLA). The PBS/PLA blends with a ratio of 20/80 and added 1% BPO was chosen because of its favorable properties. The compatibility of PBS/PLA was improved after adding BPO. The addition of BPO also improved the crystallization and promoted the complete decomposition of PBS/PLA, respectively. The blends with BPO was degraded by proteinase K. The degradation rate of the blends reached 67% after 96 h degradation. The PLA was not degraded completely because of the crosslink between PBS and PLA.

Preparation and characterization of alginate-PVA-based semi-IPN: controlled release pH-responsive composites

Abstract: The objective was to develop naturally derived polymer-based hydrogels with high mechanical strength and a controlled delivery of drug for extended period of time. Here, we report the fabrication of chemically cross-linked polyvinyl alcohol-graft-poly(acrylic acid)/sodium alginate hydrogel as a semi-interpenetrating polymer network (SIPN). For the preparation of SIPN hydrogels, SA and PVA were cross-linked with AA monomer in the presence of co-monomer EGDMA through free-radical polymerization reaction, using APS as an initiator. Loxoprofen sodium was loaded as a model drug. FTIR, XRD, TGA, and DSC were performed for the characterization of copolymer. Surface morphology was studied by SEM. Swelling studies were carried out at low and higher pH to evaluate pH-dependent swelling of formed SIPN hydrogels. FTIR, XRD, TGA, and DSC studies confirmed the formation of a new copolymer. Developed SIPN hydrogels showed maximum swelling, drug loading, and drug release at pH 7.4 while low at pH 1.2. Moreover, formulations with higher AA contents showed maximum swelling at 7.4 pH. High drug loading and higher drug release have been observed at pH 7.4. In vitro release profile of loxoprofen sodium was found dependent on pH, concentration of monomers, and cross-linking agent. Gel% and yield% for the prepared SIPN hydrogels were determined and found that gel% or yield% is directly proportional to the concentration of polymers, i.e., SA and PVA, due to their behavior as macromolecule radicals for monomer. The results from FTIR analysis showed that both SA and PVA react with the acrylic acid monomer during the polymerization process and result into the formation of SIPN. The formation of semi-IPN structure significantly improved the surface morphology of SIPN hydrogels as evident by SEM, which corresponds to their improved swelling ability and mechanical strength. Drug release mechanism from the formed SIPN was explained by kinetic modeling and found that first-order, Higuchi model, and Korsmeyer–Peppas model are the best fit models to explain drug release from hydrogels. Conclusively, prepared hydrogels were highly pH-responsive and showed good mechanical strength and time-dependent drug release. SIPN hydrogels could be a potential carrier network for controlled delivery of loxoprofen sodium for extended period of time.

Thermal degradation of poly(caprolactone), poly(lactic acid), and poly(hydroxybutyrate) studied by TGA/FTIR and other analytical techniques

Abstract: Thermal degradation of three biodegradable polyesters: poly(caprolactone), poly(lactic acid), and poly(hydroxybutyrate), was studied by thermogravimetry coupled to Fourier Transform Infrared Spectroscopy TGA/FTIR before and after they were partially degraded. TGA curves and Gram–Schmidt plots showed only one decomposition stage for both poly(caprolactone), PCL, and poly(lactic acid), PLA. In contrast, poly(hydroxybutyrate), PHB, exhibited two degradation stages by TGA, but only one region of evolved gases was appreciated in the Gram–Schmidt plot. It was established that hexenoic acid, e-caprolactone, and small fragments of polymeric chains are the main degradation products of PCL, which were simultaneously released during thermal decomposition of this polymer. Meanwhile, carboxylic acid, aldehydes, and lactide monomer and/or oligomers were evolved from degradation of PLA. Finally, carboxylic acids and ester moiety were detected in the course of degradation of PHB; thus, random chain scission reaction took place during thermal decomposition of this polymer. Results from the spectroscopic characterization (FTIR and 1H NMR) of partially degraded samples supported the degradation mechanisms suggested by TGA/FTIR studies.

Polymer flooding and its combinations with other chemical injection methods in enhanced oil recovery

Abstract: In this paper, the current advances in chemical injection method of polymer flooding are reviewed. The ultimate goal of polymer flooding for EOR process is to improve tertiary oil recovery by increasing the overall oil driving efficiency as a result of the improvements in injected fluid’s viscosity and mobility ratio. However, it was found that there were some limitations of polymer flooding. Hence, this paper will be reviewing studies on combinations of polymer flooding with other chemical methods by various researchers. Polymer flooding and its combinations with other flooding methods discussed in this paper are: polymer, alkaline polymer (AP), micellar polymer (MP), nanoparticles injection with polymers (NP) and alkaline surfactant polymer (ASP). The working principle, resistance, effectiveness and field application of each flooding method are also reviewed and compared.

A novel and homogeneous scaffold material: preparation and evaluation of alginate/bacterial cellulose nanocrystals/collagen composite hydrogel for tissue engineering

Abstract: Alginate is a well-known biomaterial which has been widely used in tissue engineering due to its excellent property However, there are still several drawbacks, such as weak mechanical strength, the lack of cell recognition sites for cell adhesion, extensive swelling and uncontrolled degradation that limit its practical application Therefore, the internal gelation using CaCO3–GDL complex and the incorporation of bacterial cellulose nanocrystals (BCNs) and type I collagen (COL) as the reinforcing component into alginate matrix were proposed to prepare the novel and homogeneous alginate/bacterial cellulose nanocrystals/collagen composite scaffold (ALG/BCNs/COL) The morphology, porosity, mechanical property, swelling and degradation behavior, and cytotoxicity of the resultant scaffold were investigated The experimental results showed that ALG/BCNs/COL revealed good three-dimensional (3D) architecture as well as lamellar and porous morphologies The incorporation of BCNs into alginate matrix obviously decreased the pore size and maintained the porosity of ALG/BCNs/COL, which was in favour of mechanical integrity FT-IR spectra and XRD analysis revealed that the components of ALG/BCNs/COL, such as SA, BCNs and COL were combined together by intermolecular hydrogen bonds, which could effectively inhibit large swelling and retard the biodegradation of the composite scaffold Finally, cell studies results indicated that both MC3T3-E1 and h-AMS cells were viable and proliferate well on the composite scaffold

Modification of epoxy resin by silane-coupling agent to improve tensile properties of viscose fabric composites

Abstract: The modification of epoxy resin by 3-aminopropyltriethoxysilane (APTES) to improve the tensile properties of warp knitted viscose fabric composites is reported in this study. The study evaluates th ...

Immobilization of horseradish peroxidase on electrospun poly(vinyl alcohol)–polyacrylamide blend nanofiber membrane and its use in the conversion of phenol

Abstract: Electrospun nanofibers, with their porous structures, high surface-to-volume ratio, and good mechanical properties, are used as a support material for enzyme immobilization. In this study, the poly(vinyl alcohol) and polyacrylamide bicomponent (PVA–PAAm) nanofibers were fabricated via the electrospinning method. Synthesized PAAm was characterized with size exclusion chromatography (SEC). Nanofibers were characterized by fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscope (SEM). DSC and TGA analyses showed that the nanofibers were more durable than PVA and PAAm polymers. SEM images demonstrated that all nanofibers possessed uniform and smooth structures (average diameter about 300 nm). FTIR results have shown that PAAm successfully participates in nanofiber structure. The produced nanofibers were used as support material for covalent immobilization of horseradish peroxidase (HRP). The optimum temperature for free HRP was 45 °C, whereas it was 50 °C for the immobilized enzyme. The immobilized HRP showed better storage and thermal stability than free HRP. The kinetic parameters (K m and V max) were found to be 2.42 mM and 0.027 U for the immobilized HRP and 1.86 mM and 0.079 U for the free HRP, respectively. The immobilized enzyme could be used effectively for 25 cycles with 54% retention of the activity. The immobilized HRP was also used for the conversion of phenol. Phenol removal was found to be about 29.68% at 180 min in real wastewater. The novel PVA–PAAm nanofibrous material was successfully used as a support material for covalent immobilization of HRP. Immobilized enzymes such as oxido-reductases onto the PVA–PAAm bicomponent nanofiber could be recommended in the treatment of organic pollutants in industrial effluents.

Grafted cellulose: a bio-based polymer for durable applications

Abstract: Grafting is one of the best method for the modification of physicochemical properties of the cellulose. The –OH groups present at C2, C3, and C6 atoms of each β-d-glucopyranose units of cellulose chains are the most susceptible active sites for the grafting of many monomer units or polymers for the formation of a variety of cellulose-based graft copolymers with advanced properties and potential applications as compared to the bare cellulose. In this review article, a brief introduction to get an insight into the structural features of cellulose is given. After that, the potential applications and recent advancements of various cellulose graft copolymers made in fields of controlled drug delivery, adsorption of harmful, toxic and non-biodegradable dyes from industrial effluents, sorption of heavy metal ions from aqueous medium, modification of electrolyte, electrodes and separators of the modern age Lithium ion batteries, and fabrication of smart and innovative food packaging materials are reviewed.

Incorporation of CuO nanoparticles into thin-film composite reverse osmosis membranes (TFC-RO) for antibiofouling properties

Abstract: The effect of the incorporation during the interfacial polymerization process of copper-oxide (CuO) nanoparticles in thin-film composite (TFC) reverse osmosis (RO) membrane on their antibiofouling and desalinization performance have been studied. Membranes were characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), zeta potential and contact angle measurements. Bactericidal tests were performed using Escherichia coli and anti-adhesion properties were confirmed by fluorescence microscopy. Membrane performance using a cross flow cell was evaluated. XRD and SEM–EDX analyses confirmed the incorporation of these nanoparticles into the membrane. Similar contact angle, higher surface roughness and less negatively charged surface on modified membrane compared to that of the pristine membrane were observed. However, an excellent anti-adhesion and bactericidal effect were observed, mainly attributed to the copper toxicity. The desalination performance of the modified membrane showed an important salt rejection with stable water flux. In conclusion, the incorporation of CuO nanoparticles into TFC-RO membranes during the interfacial polymerization process is a potential alternative method to improve the antibiofouling capacities without impairing the performance of the membrane.

Fabrication of polyaniline–few-layer MoS2 nanocomposite for high energy density supercapacitors

Abstract: Polyaniline–few-layer molybdenum disulfide nanocomposite (PANI–MoS2) has been synthesized by in situ polymerization of aniline over MoS2 using HCl as the dopant. X-ray crystallographic studies show the characteristic peaks of few-layered MoS2 in the PANI matrix. The changes in Raman and UV–Vis spectra have proved that there are definite interactions between PANI and few-layer MoS2.PANI–MoS2 nanocomposite as an electrode material for supercapacitor exhibits a maximum specific capacitance of 687 Fg−1 at a scan rate of 5 mVs−1 using cyclic voltammetry (CV) and a Csp of 612 Fg−1 at a current density of 0.2 Ag−1 using chronopotentiometry (CP). Further, the material also exhibits a high energy density of 128 Wh kg−1with a maximum power density of 9.8 kW kg−1 and a tremendous cyclic stability with 93% capacitance retention after 2000 cycles. These superior electrochemical results over bare PANI and MoS2 showed the PANI–MoS2 nanocomposites to be a capable electrode material for energy storage systems.

Preparation and dielectric properties of PVP-based polymer electrolyte films for solid-state battery application

Abstract: Solid polymer electrolyte has been prepared with the combination of PVP (poly vinyl pyrrolidone) and magnesium sulfate heptahydrate (MgSO4·7H2O) by solution cast technique and subsequently characterized for possible polymer battery application. Structural studies were carried out by XRD technique. DSC analysis revealed that the micro-porous polymer membrane is thermally stable up to 300 °C. The surface morphology of the films was analyzed by SEM. Electrical conductivity was performed using AC impedance analyzing technique in the frequency range from 4 kHz to 5 MHz. Complex impedance spectroscopy revealed that the enhancement in electrical conductivity by salt doping and the conductivity maximum was obtained for 15 wt% of MgSO4·7H2O salt concentration. Optical absorption studies were carried out on to the prepared films in the wavelength range 200–600 nm. Solid-state polymer battery has been fabricated with the configuration of Mg+/(PVP + MgSO4·7H2O)/(I2 + C + electrolyte) and discharge characteristics were studied for a constant load of 100 kΩ. The cell parameters like open-circuit voltage, short circuit current, energy density and power density were calculated.

Polyurethanes in cardiovascular prosthetics

Abstract: Polyurethane has become a popular material in biomedical industry because of its good mechanical properties as well as biocompatibility and hemocompatibility. However, the material degrades during a long-term functioning of polyurethane grafts. To increase biostability, novel polyurethanes with a siloxane segment, polycarbonate polyurethanes, and nanocomposite polyurethanes are offered. Along with novel polyurethanes, modern tissue engineering technologies are well applicable for manufacture of the polyurethane products with unique properties. Different polyurethanes and modern technologies for producing cardiovascular grafts of polyurethane are discussed.

Dynamics of nucleation and growth mechanism in the presence of nanoparticles or block copolymers: polystyrene/poly(vinyl methyl ether)

Abstract: This study aimed at controlling the phase separation kinetics in the metastable region of polystyrene/poly(vinyl methyl ether) (PS/PVME) blend by adding a block copolymer or hydrophilic and hydrophobic nanoparticles as the compatibilizer. We studied the effects of compatibilizer localization and volume fraction on the dynamics of nucleation and growth (NG) mechanism. For this purpose, time sweep experiments were performed using rheological analysis and phase contrast optical microscopy. Based on the results, hydrophilic nanosilica with preferential affinity to the PVME-rich matrix phase slowed down efficiently the phase separation and beyond a critical volume fraction, pinned the domain growth. The block copolymer, self-assembling along the interface, caused a considerable decrease in phase separation kinetics as well. However, its efficiency was lower than the hydrophilic nanosilica and in the range of the applied volume fractions, no pinning behavior was observed. The hydrophobic nanosilica which preferentially wetted the PS-rich droplets had the minimal effect on phase separation. It was observed that adding nanoparticles or block copolymer could change the dynamical scaling of phase separation.

Concentration-dependent behaviors of ZnO-reinforced PVA–ZnO nanocomposites as electron transport materials for OLED application

Abstract: The laboratory synthesis of pure PVA and PVA–ZnO nanocomposites of varying concentrations was synthesized via co-precipitation and in situ techniques, respectively. The formation of PVA and PVA–ZnO nanocomposites and the corresponding changes in their structural properties were examined using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopic techniques. The FESEM images displayed regular distribution of ZnO nanowires in PVA matrix. The UV–Vis absorption spectra showed that the direct band gap (E g) decreased with the increase in ZnO concentration. The UV–Vis spectra also indicated the shifting towards blue–green region for higher ZnO concentrations. The optimized direct band gap was estimated around 2.985 eV duly associated with the p-type conductivity. The photoluminescence (PL) study revealed optimum intensity for 5:2 ratio of PVA:ZnO nanocomposites and blue emission (470 nm) varied with the increase in ZnO concentration. The atomic force microscopy (AFM) study showed that RMS roughness of the nanocomposites increased with the increase in ZnO concentration. The enhanced current density (~ 237.83%) in the visible region and reduced optical band gap with relatively higher electron–hole non-radiative recombination rate was in good agreement with the data for electron transport layer material for organic light emitting diode (OLED) application.

Development of room temperature ethanol sensor from polypyrrole (PPy) embedded in polyvinyl alcohol (PVA) matrix

Abstract: Polypyrrole (PPy) is embedded in polyvinyl alcohol (PVA) matrix to give a homogeneous composite solution by dispersing PPy in PVA solution. Scanning electron microscopic (SEM) study on the film prepared from the composite solution shows uniform distribution of nearly spherical shaped PPy grains of average diameter of 20 nm. The X-ray diffraction (XRD), UV–visible and Fourier transform infra-red (FTIR) spectroscopic characterizations of the composite film are carried out for structural and optical properties. The enhanced thermal stability of the PPy–PVA composite film is confirmed by thermogravimetric analysis (TGA). XRD shows signature of amorphous nature for PVA along with some crystallinity arising for PPy. UV–visible absorption spectrum shows two absorption peaks for π–π* and polaronic transition; FTIR spectrum suggests cross linking between PPy and PVA. Studies on sensing of the PPy–PVA composite film for ethanol, ammonia, toluene, chloroform and acetone vapors at room temperature (300 K) are done for comparison. The composite film shows best response among all these vapors towards ethanol requiring smallest response time.

Preparation and physical characteristics of epoxy resin/ bacterial cellulose biocomposites

Abstract: Using bacterial cellulose (BC) prepared from Vietnamese nata-de-coco via an alkaline pre-treatment followed by a solvent exchange process, epoxy resin (EP)/BC biocomposites were fabricated using three different dispersion techniques: mechanical stirring only, both mechanical stirring and grinding, and both mechanical stirring and ultrasonication. The surface of BC was modified with a silane coupling agent to improve the chemical affinity between BC and epoxy resin. The biocomposite materials comprising BC, epoxy resin, and methylhexahydrophthalic anhydride as a curing agent were obtained from hot curing processing. The morphology and mechanical properties such as fracture toughness, enhanced K IC values, and tensile and flexural properties of the bio-based composites were compared with those of the virgin epoxy resin. The silane coupling agent had a vital role in improving the mechanical characteristics of the bio-based composites. For instance, K IC values, tensile strength, Young’s modulus, and flexural strength of the 0.3 wt% BC/epoxy composites with the presence of 2.0 wt% silane coupling agent were 0.7740 MPa m1/2, 53.32 MPa, 1.68 GPa, and 83.05 MPa. These values represent improvements of 36.77, 17, 15.86, and 14.42%, respectively, compared to a neat epoxy resin. Scanning electron microscopy revealed the rough fracture surface of epoxy resin/BC-based biocomposites with a multipathway crack, requiring more energy before breakage.

Influence of expandable graphite particle size on the synergy flame retardant property between expandable graphite and ammonium polyphosphate in semi-rigid polyurethane foam

Abstract: Effect of the difference of expandable graphite (EG) particle size on the synergistic flame retardant effect between expandable graphite (EG) and ammonium polyphosphate (APP) in the semi-rigid polyurethane foam (SPUF) was studied for the first time. Three large-span particle sizes of EG were added into SPUF with different mass ratios of EG/APP. The synergistic effect between EG and APP on the flame retardant property of composites was investigated using the limiting oxygen index test, horizontal–vertical burning test, thermogravimetric analysis (TGA), scanning electron microscope (SEM), etc. Flammability performance tests indicated that the larger particle size the EG possessed, the more obvious will be the synergistic effect exhibited between EG and APP. SEM images and TGA results provided positive evidence for the combustion tests. Synergistic effect was strongly influenced by the compactness of united protective layer. The maximal rate of the degradation of the SPUF composite system further confirmed the relationship between the rate of the composites’ degradation and the compactness of united protective layer. Speculative reactions which were related to the changes of EG in the presence of APP under high temperature were discussed.

Band structure and optical properties of polyaniline polymer material

Abstract: The present contribution reports on the electronic structure and optical properties of the polyaniline polymer material. The calculations are performed using ab initio total energy calculations within the full-potential linearized augmented plane wave method in the framework of the density functional theory. The generalized gradient approximation is used to treat the effects of exchange and correlation. The fundamental band-gap energy and static and high-frequency dielectric constants of the polymer of interest are predicted. The optical spectra against the photon incident energy along both the x- and z-axis are presented and examined.

Castor oil as potential multifunctional additive in the formulation of eco-friendly lubricant

Abstract: The article investigates the performance of polymers prepared from castor oil and dodecyl acrylate as biodegradable multifunctional additive in the formulation of eco-friendly lubricant. Homopolymer of castor oil and its copolymers with dodecyl acrylate (DA) at different percentage ratios (w/w) were synthesized using azobisisobutyronitrile (AIBN) as initiator without any solvent. The polymers were characterized by spectral techniques (FT-IR and NMR spectroscopy). The molecular weight of all the prepared polymers was determined by gel permeation chromatography (GPC). The thermal stability of the polymers was determined by thermogravimetric analysis (TGA). Performance evaluation of all the prepared polymers in SN150 mineral oil as viscosity index improver (VII), pour point depressant (PPD) and antiwear were carried out according to standard ASTM methods. The action mechanism of the additives as PPD was studied by photo micrographic image. Biodegradability of all the samples was tested through soil burial test (SBT).

Electrospun polyurethane microporous membranes for waterproof and breathable application: the effects of solvent properties on membrane performance

Abstract: Electrospun polyurethane (PU) based nanofibrous mats were fabricated from the solutions prepared with different volume ratios of N,N-dimethylformamide (DMF), methanol (MeOH), and dichloromethane (DCM). The membrane structures such as the nanofiber diameter, the pore size distribution, and the porosity were investigated in detail. And the morphological, mechanical, waterproof, and breathable properties of the membranes were used to estimate the characteristics of the membranes. Various solutions were compared to obtain porous nanofibrous membranes without beads or curls, which revealed that morphologies of PU fibrous membranes could be finely regulated by tuning the solvent volume ratios and the solution concentrations. The results showed that the nanofibrous membranes with the DMF/DCM solvents exhibited the high fiber diameter (500–700 nm) and the wide pore size distribution (0.6–1.2 µm). Besides, the water contact angle (WCA) of the PU nanofibrous film using the 100% DMF was 133°, but it could not persist for a long time. And the resultant membranes presented high hydrostatic pressure to 2.1 kPa, modest water vapor transmission rate of 10.1 kg/m2/day, as well as robust mechanical properties with tensile strength of 6.6 MPa, which are desirable in many important applications including protective clothing.

Influence of solid polymer electrolyte preparation methods on the performance of (PEO–PMMA)–LiBF4 films for lithium-ion battery applications

Abstract: Classical solution-cast and ultrasonic–microwave-irradiated solution-cast methods have been used for the preparation of solid polymer electrolyte (SPE) films comprising polymer matrix of poly(ethylene oxide) and poly(methyl methacrylate) blend and lithium tetrafluoroborate (LiBF4) ionic salt. These films have been characterized by employing the X-ray diffraction, Fourier transform infrared spectroscopy, dielectric relaxation spectroscopy, and electrochemical analyser. It is observed that the temperature-dependent ionic conductivity of these predominantly amorphous solid ion–dipolar complexes is governed by their dielectric permittivity and the relaxation times of various dynamical processes. The relaxation times and the dc ionic conductivity of these electrolyte materials obey the Arrhenius behaviour, whereas the normalized ac conductivity exhibits the time–temperature superposition scaling. The influence of sample preparation methods on the performance of SPE films and the suitability of these materials for the lithium-ion batteries has been explored by noting the relative changes in their structural, dielectric, electrical, ionic conductivity, and the electrochemical parameters.

Preparation and toughening performance investigation of epoxy resins containing carbon nanotubes modified with hyperbranched polyester

Abstract: In this paper, the carboxylic multi-walled carbon nanotube (MWCNTs-COOH) was modified with hyperbranched polyester via surface graft, and then the epoxy/MWCNTs-COOH composites were prepared to explore the influences of surface modification of MWCNTs-COOH using hyperbranched polyester on the mechanical performance of the composites. The results of TGA and FT-IR of the grafted MWCNTs-COOH (named MWCNTs-H20) indicated that the hyperbranched polyester was successfully grafted onto MWCNTs-COOH by esterification reaction between carboxyl groups on the surface of MWCNTs-COOH and the hydroxyl groups of hyperbranched polyester. The results of fluorescence microscope elucidate that compared with raw MWCNTs-COOH, the grafted MWCNTs-H20 receives a better dispersion in the epoxy prepolymer. Moreover, MWCNTs-COOH and MWCNTs-H20 were, respectively, added into epoxy prepolymer to prepare the EP/MWCNTs composites. The results of DMA revealed that the addition of MWCNTs-COOH enhanced the low temperature toughness of the neat EP, and the surface grafting of hyperbranched polyester onto MWCNTs-COOH further decreased the glass transition temperature of the composites and exhibited a better performance in the enhancement in toughening EP. The measurement of the mechanical performances and surface morphology revealed that the addition of MWCNTs-H20 enhances tensile strength, elongation at break and Charpy impact strength of the EP/MWCNTs composites significantly, resulting in a better toughness of the composites; however, it had little influence on the Barcol hardness.

Hydrogel nanocomposites based on chitosan-g-polyacrylamide and silver nanoparticles synthesized using Curcuma longa for antibacterial applications

Abstract: Hydrogel nanocomposites based on chitosan-g-polyacrylamide and silver nanoparticles (Cs-g-PAAm/AgNPs) were developed by simple, cost effective, and eco-friendly process at room temperature. First, the hydrogels were prepared via grafting copolymerization and crosslinking of acrylamide (AAm) onto chitosan (Cs) with various weight ratios, using potassium persulfate as initiator and N,N′-methylenebisacrylamide as crosslinker, and then hydrolyzed to achieve materials with uppermost swelling properties. Finally, the AgNPs were biosynthesized and entrapped into hydrogels as templates using aqueous silver nitrate as precursor and Curcuma longa tuber extract as both reducing and stabilizing agents. The influences of the templates and the silver precursor concentrations on the AgNP formation and the properties of the elaborated nanocomposites were investigated. The UV–visible spectroscopy has confirmed the occurrence of the nanosilver particle formation, while the X-ray diffraction analysis has evidenced their face-centered cubic crystalline phase. The inductively coupled plasma analysis has revealed that the extent of AgNPs into the network increases by a decrease in Cs weight ratios and an increase in AgNO3 concentrations. Transmission electron microscope images have showed a spherical shape of AgNPs with average sizes <26 nm. Interactions between hydrogel functional groups and those of proteins extracted from C. longa, which are probably the capping ligands of the AgNPs, were suggested from Fourier transform-infrared spectroscopy. Slight enhance in thermal stability of nanocomposites was noticed from thermogravimetric analysis. Besides, the swelling and retention capacities were affected by both Cs and AgNP contents. Furthermore, the swelling kinetics was found to obey the second-order model with non-Fickian diffusion. The antibacterial activity against Staphylococcus aureus and Escherichia coli bacteria was examined by both zone inhibition and dynamic shake flask methods and the results have showed an efficient activity of AgNP-loaded hydrogels with a maximum of killing ratio of 99.99%. Finally, it is suggested that the optimized hydrogel nanomaterials can be candidates for bio-applications.

Synthesis, photophysical and electrochemical properties of polyimides of tetraaryl imidazole

Abstract: The new tetraaryl substituted imidazole-based diamines were designed and synthesized through Debus–Radziszewski imidazole synthesis, and characterized by FT-IR, 1H NMR spectroscopy and MASS spectroscopy. A series of new fluorescent polyimides (PI) were prepared by polymerization of the tetra substituted imidazole diamines with tetracarboxylic dianhydrides, such as pyromellitic dianhydride, naphthalene tetra carboxylic dianhydride and perylene tetra carboxylic dianhydride. These polymers were readily soluble in a variety of organic solvents and they also possess good thermal stability. The glass transition temperature of these polymers was in the range of 398–453 °C. The ultraviolet–visible absorption spectra showed that all of the polymers had absorption maxima around 344–521 nm with a fluorescence emission maxima around 420–531 nm. The electrochemical band gaps of PI-1, PI-2 and PI-3 copolymers are estimated to be 2.37, 2.17 and 2 eV, respectively. Similarly, the optical band gap of PI-1, PI-2 and PI-3 copolymers was found to be 3.15, 3.05, and 2.15 eV, respectively. These polymer exhibits fluorescence quantum yield of 0.65, 0.46, and 0.3% for PI-1, PI-2 and PI-3, respectively. The PIs also exhibited good flame retardant behavior.

Preparation and characterization of chitosan–poly(vinyl alcohol)–neomycin sulfate films

Abstract: The aim of our study was obtaining chitosan–poly(vinyl alcohol)–neomycin sulfate films (Cs–PVA–Ne) by using solvent casting technique and the characterization of the products. The films were analyzed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, thermogravimetry (TG and DTG), differential scanning calorimetry (DSC), contact angle (CA) measurements, mechanical, and antibacterial activity tests. FTIR and DSC analysis demonstrated that interaction between Cs, PVA, and Ne took place. Static water CA measurements showed an improvement in the hydrophilicity of the Cs–PVA–Ne films. Also, the drug-loaded films proved to have fairly good mechanical strength and significant effects against Staphylococcus aureus and Escherichia coli. The unloaded films show minimum bacterial inhibition (~ 10.00 mm) compared to drug-loaded films (~ 30.00 mm). The bacterial inhibition was higher in all the cases of S. aureus than E. coli. Furthermore, PVA was found to improve the films properties. Due to their physical–chemical and mechanical features and the excellent antibacterial properties, the obtained Cs–PVA–Ne films are suitable for their use as wound-dressing materials.

Aging of silicone pressure-sensitive adhesives

Abstract: Silicone pressure-sensitive adhesives (Si-PSA) exhibit unique properties, such as high Si–O–Si backbone flexibility, low intermolecular interactions, low surface tension, excellent thermal stability, and high UV transparency, which often explains why silicone PSAs have an impressive performance at high- and low-temperature extremes, excellent electrical properties, chemical resistance, and outstanding weathering resistance turning them superior compared to organic PSAs. It is well known that due to their unique properties, silicone pressure-sensitive adhesives are materials for special applications. In the present study, we focus on changing the useful properties of the best compositions of silicone pressure-sensitive adhesives in time to verify the impact of aging on them. The influence of time on given silicone pressure-sensitive adhesive tapes and their useful properties is a very important factor for the description of the life-time of potential products based on such compositions. Aging of Si-PSA was carried out for 1 h, 24 h, 7 days, 31 days, and 92 days. The tests did include such properties like adhesion, cohesion (at 20 and 70 °C), tack, and yellowness.

Synthesis of alginate/nanocellulose bionanocomposite for in vitro delivery of ampicillin

Abstract: In this study, ampicillin drug loaded with alginate and nanocellulose film was prepared by solution casting method. Nanocellulose and ampicillin incorporated into alginate to improve both mechanical and swelling properties. Interaction of ampicillin with alginate and nanocellulose was proved by ATR-FTIR spectra. The formulated ampicillin loaded Alg/NC film gave acceptable physicochemical properties compared with Alg-amp film and was able to deliver the drug in a prolonged release pattern. In vitro drug release showed that alginate could provide an immediate release of ampicillin with further enhanced nanocellulose, and followed by a sustained release over 500 min of the remaining drug. The present study exhibited a simple and useful approach to systematically design for providing drug release profiles.