Showing papers in "Journal of Polymer Research in 2018"

Excellent corrosion protection performance of epoxy composite coatings filled with silane functionalized silicon nitride

Abstract: Silicon nitride was firstly used as anticorrosive pigment in organic coatings. An effective strategy by combining inorganic fillers and organosilanes was used to enhance the dispersibility of silicon nitride in epoxy resin. The formed nanocomposites were applied to protect Q235 carbon steel from corrosion. The anticorrosive performance of modified silicon nitride with silane (KH-570) was investigated by electrochemical impedance spectroscopy (EIS), water absorption and pull-off adhesion methods. With the increase of immersion time, the corrosion resistance as well as adhesion strength of epoxy resin coating and unmodified silicon nitride coating decreased significantly. However, for the modified silicon nitride coating, the corrosion resistance and adhesion strength still maintained 5.7×1010 Ω cm2 and 7.6 MPa after 2400-h and 1200-h immersion, respectively. The excellent corrosion resistance performance could be attributed to the chemical interactions between KH-570 functional groups and silicon nitride powders, which mainly came from the easy formation of Si-O-Si bonds. Furthermore, the modified silicon nitride coating formed a strong barrier to corrosive electrolyte due to the hydrophobic of modified silicon nitride powder and increased bonds.

Study of the structural order of native starch granules using combined FTIR and XRD analysis

Abstract: The structural order of native starch granules with different crystalline patterns was analyzed by combined X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) and the results were compared to that of X-ray diffraction (XRD). The FTIR spectra of 13 starch samples were evaluated by principal component analysis (PCA). The main differences among the polymorphs were observed in the intensity of two regions: the OH vibration region, 3650–3000 cm−1, and the region of major adsorption bands, 1200–800 cm−1. The variation in these regions showed that two different groups can be distinguished, one for B-type starches and one for A- and C-type starches. A-type starches exhibited a well-resolved band at 1022 cm−1, suggesting that A-type starch granules have a greater amount of ordered short-range double helices than B-type starches. The intensity and shape of the OH band were different for the three starches and were associated with different local molecular environments of the two water populations of the starch granule. The PCA analysis for X-ray diffraction patterns showed a clear segregation between A- and B-type starches, defined by three typical diffraction peaks at 2θ = 15.0°, 18.1° and 23.1° for A-type starches. There was no correlation in the crystallinity degree obtained by the FTIR and XRD methods.

Polyurethanes from vegetable oils and applications: a review

Abstract: Among the various polymers, polyurethanes are likely the most versatile specialty polymers. These polymers are widely used in many applications such as foams, coatings, insulations, adhesives, paints and upholstery. Similar to many polymers, polyurethanes relies on petrochemicals as raw materials for its major components. Indeed, nowadays many researches have focused to replace petroleum-based resources with renewable ones to improve polyurethanes sustainability. Polyurethanes are synthesized by polymerization reactions between isocyanates and polyols. Only a few isocyanates are commonly used in polyurethane industries, while a variety of polyols are available. Renewable materials such as vegetable oils are promising raw materials for the manufacture of polyurethane components such as polyols. Vegetable oils are triglycerides which are the esterification product of glycerol with three fatty acids. Several highly reactive sites including carbon-carbon double bond, allylic position and ester group in triglycerides and fatty acids open the opportunities for various chemical modifications for new polyol with different structures and functionalities. Different methods such as are epoxidation, ozonolysis, hydroformylation and metathesis have been widely studied to synthesise bio-polyol from vegetable oil for new polyurethanes, which depend on triglyceride and isocyanate reagents used. The incorporation of a vegetable oil moiety can enhance thermal stability and mechanical strength of polyurethanes. Similar to bio-polyol, the development of renewable resource based bio-isocyanates is also gained attention to produce entirely bio-polyurethanes. This article comprehensively reviews recent developments in the preparation of renewable resource based polyols and isocyanates for producing polyurethanes and applications.

Poloxamers, poloxamines and polymeric micelles: Definition, structure and therapeutic applications in cancer

Abstract: Research for new therapies to treat diseases like cancer, it is one of the focus of Health Sciences. Nowadays, the available therapeutic strategies have in many cases limitations and undesired side effects, which shows a need to find new therapies with a higher efficacy. In this regard, over the past few years, poloxamers and poloxamines have been gaining more attention in the pharmaceutical field, mainly due to their advantages as potential nanosystems. Therefore, poloxamers and poloxamines are amphiphilic block of copolymers constituted by PEO units, poly(ethylene oxide), and PPO units, poly(propylene oxide), presenting the capability to self-assembly in micellar structures in aqueous medium forming polymeric micelles, which improve theirs potential as drug and genetic material nanocarriers. Thereby, in order to create new alternative treatments for current pathologies, like cancer, alterations in the poloxamines and poloxamers, the combination of these with other polymers and the conjugation with ligands are being introduced as a viable option to allow the combination of therapies, such as the simultaneous delivery of a gene and a drug in the same system. These intelligent stimuli-sensitive systems, with well-defined structures and functionalities, make possible the development of a safe, specific and effective therapeutic strategy. Thus, this article intends to review several aspects of poloxamines and poloxamers concerning their general properties and their applications in drug and gene delivery. Also, are reviewed the preparation and characterization techniques of polymeric micelles with a focus in micelleplexes which can be used as a simultaneous drug and nucleic acid carrier.

Design and synthesis of porous polymeric materials and their applications in gas capture and storage: a review

Abstract: The design and synthesis of porous organic materials that have increasing physical and chemical characteristics have been discussed. For example, a variety of porous organic polymers, metal–organic frameworks, conjugated microporous polymers, and polymers of intrinsic microporosity have been designed and synthesized using simple and efficient procedures. Such materials have unique gas adsorption properties and can be used in gases separation and storage. In addition, they have high surface area, porosity, and selectivity towards carbon dioxide compared to other gases such as nitrogen and methane.

Investigations on the performances of treated jute/Kenaf hybrid natural fiber reinforced epoxy composite

Abstract: Natural fiber composite laminates are nowadays used in structural application such as aerospace, automobile and in sports goods because of their high strength to weight ratio and renewability. Hence the study of mechanical behaviors of natural fiber composites is very important in using these composite laminates for such specific applications. This project aims at identifying the mechanical properties of hybrid natural Jute/Kenaf fiber. The major drawbacks in natural fiber are its Resin incompatibility. Surface treatment of fiber is made to improve the interfacial bonding between the fiber and resin and to reduce the moisture absorption. Laminates are fabricated using Hand lay-up technique. Mechanical properties such as tensile, flexural, and Impact test for jute/kenaf hybrid laminates were obtained. Specimen preparation and Mechanical property testing were carried out as per ASTM standards. Micro structures of the different layer of hybrid specimens are scanned by the Scanning Electron Microscope.

Fabrication and characterisation of nanofibrous polyurethane scaffold incorporated with corn and neem oil using single stage electrospinning technique for bone tissue engineering applications

Abstract: In bone tissue engineering, the design of scaffolds with ECM is still challenging now-a-days. The objective of the study to develop an electrospun scaffold based on polyurethane (PU) blended with corn oil and neem oil. The electrospun nanocomposites were characterized through scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), contact angle measurement, atomic force microscopy (AFM) and tensile strength. The assays activated prothrombin time (APTT), partial thromboplastin time (PT) and hemolysis assay were performed to determine the blood compatibility parameters of the electrospun PU and their blends of corn oil and neem oil. Further, the cytocompatibility studies were performed using HDF cells to evaluate their proliferation rates in the electrospun PU and their blends. The morphology of the electrospun PU blends showed that the addition of corn oil and corn/neem oil resulted in reduced fiber diameter of about 845 ± 117.86 nm and 735 ± 126.49 nm compared to control (890 ± 116.911 nm). The FTIR confirmed the presence of corn oil and neem oil in PU matrix through hydrogen bond formation. The PU blended with corn oil showed hydrophobic (112° ± 1) while the PU together with corn/neem oil was observed to hydrophilic (64° ± 1.732) as indicated in the measurements of contact angle. The thermal behavior of prepared PU/corn oil and PU/corn/neem oil nanocomposites were enhanced and their surface roughness were decreased compared to control as revealed in the AFM analysis. The mechanical analysis indicated the enhanced tensile strength of the developed nanocomposites (PU/corn oil - 11.88 MPa and PU/corn/neem oil - 12. 96 MPa) than the pristine PU (7.12 MPa). Further, the blood compatibility assessments revealed that the developed nanocomposites possess enhanced anticoagulant nature compared to the polyurethane. Moreover, the developed nanocomposites was non-toxic to red blood cells (RBC) and human fibroblast cells (HDF) cells as shown in the hemolytic assay and cytocompatibility studies. Finally, this study concluded that the newly developed nanocomposites with better physio-chemical characteristics and biological properties enabled them as potential candidate for bone tissue engineering.

Construction and evaluation of the hydroxypropyl methyl cellulose-sodium alginate composite hydrogel system for sustained drug release

Abstract: We prepared a hydroxypropyl methyl cellulose-sodium alginate (HPMC-SA) composite hydrogel with a membrane covering the semi-interpenetrating network based on a semi-synthetic polymer hydroxypropyl methyl cellulose (HPMC) and a natural polymer sodium alginate (SA) by Ca2+ crosslinking and polyelectrolyte complexation with chitosan (CS) covering the hydrogel surface. The physiochemical properties of HPMC-SA hydrogels were evaluated by scanning electron microscopy, infrared spectrum, X-ray diffraction, and thermogravimetric analysis. The swelling ratio of the HPMC-SA composite hydrogel in simulated gastrointestinal fluid was measured. The drug release behavior of the HPMC-SA composite hydrogel for macro-molecular and small-molecule drugs was evaluated by using bovine serum albumin, metformin hydrochloride, and indomethacin as model drugs. The results showed that the HPMC-SA hydrogel had good water absorption and degradability, an increased swelling ratio of 55, and a prolonged time for maximum swelling degree of 50 h. Moreover, the hydrogel exhibited higher drug-loading capacity and improvements in the sustained release of bio-macromolecules, demonstrating its potential as a drug carrier for biomedical applications.

Novel bionanocomposite films based on graphene oxide filled starch/polyacrylamide polymer blend: structural, mechanical and water barrier properties

Abstract: Novel bionanocomposite films based on wheat starch (ST) blended high molecular weight polyacrylamide (PAM) and filled with graphene oxide nanosheets (GO) were prepared by casting/evaporation technique of the corresponding film-forming solutions (FFS). Addition of PAM was performed in order to overcome brittleness of the starch material. Physicochemical properties of the starch and ST/PAM blend films were compared in order to highlight the specific strengthening and toughening effects of PAM on the ST/PAM blend. Structural analysis by means of Fourier Transform Infrared spectroscopy by attenuated total reflectance (ATR-FTIR) technique revealed that strong hydrogen bonding interactions occurred between ST and PAM molecules and ST/PAM blend and GO nanosheets, which result in a significant enhancement of the physicochemical, thermal and mechanical properties of the ST/PAM-GO bionanocomposites. Results showed that incorporation of 1 wt% of GO into the ST/PAM blend led to a significant improvement of tensile strength by 167.17%. Moreover, water vapor permeability and moisture uptake of the ST/PAM-GO films were significantly reduced of increasing amount of GO as nanofiller.

Synthesis, structural, thermal, optical and dielectric properties of chitosan biopolymer; influence of PVP and α-Fe2O3 Nanorods

Abstract: The present work reports the influence of Polyvinylpyrrolidone (PVP) and hematite (α-Fe2O3) nanorods (NRs) on the physicochemical properties of chitosan (Cs), as an approach to broaden its medical and technological applications. Hematite NRs of 11.4 nm diameter and 87.9 nm crystallite size were prepared by a free-template chemical method. Cs, PVP/Cs and blend loaded with hematite NRs were prepared by solution casting. Significant changes in the films’ surface were clarified using the scanning electron microscope (SEM). Fourier transformation infrared spectroscopy (FT-IR) confirmed the interaction between the NRs and the NH2 and OH functional groups of Cs. DSC measurements showed one endothermic peak assigned to the water elimination, and an exothermic one, in the range 268–287 °C, attributed to the decomposition of saccharine structure in Cs. The swelling properties of the films were sensitive to the pH of the solution. PVP/Cs film showed ~ 85% transmittance in the visible region and its optical band gap narrowed from 5.4 eV to 4.05 eV after loading with 2.0 wt.% hematite. The influence of NRs content on the optical constants of the films is discussed. The dielectric properties depend on the film’ structure. The large Polaron tunneling (LPT) model is the best suitable mechanism for the electric conduction. Due to their high thermal stability and decomposition temperature, transmittance and high conductivity, the prepared films are a candidate for the packaging industry, for use in some medical applications such as treating some chronic wounds, and optical windows and fibers.

Synthesis and characterization of a novel pH-responsive nanocomposite hydrogel based on chitosan for targeted drug release

Abstract: Over the last decade, nanocomposite hydrogels have been provided a new approach for the biomedical field. In this work, a novel pH-responsive nanocomposite hydrogel was fabricated using simultaneous in situ formation of magnetite iron oxide nanoparticles and hydrogel networks of poly(acrylic acid) grafted onto chitosan. The effects of various types of precursor molecules, pH, salt, and loading pressure were examined on the swelling properties of resulting nanocomposite hydrogels. The synthesized nanocomposite hydrogel was well characterized using different instruments. In vitro drug releasing behavior of doxorubicin was studied at pH 5.4 and 7.4. The drug release mechanism was investigated through different kinetic models. These experimental results open a new opportunity to make pH-responsive nanocomposite hydrogel devices for controlled delivery of drug.

Smart hydrogels with ethylene glycol propylene glycol pendant chains

Abstract: New hydrogels based on different oligo(alkylene glycol) methacrylate (OAGMA) with inverse thermoresponse and volume phase transition temperature (VPTT) were obtained and characterised in this paper. Synthesis was performed from monomer-solvent (OAGMA-water/ethanol) mixture by simultaneous radiation-induced polymerisation and crosslinking; three different OAGMA (EG6MA, EG6PG3MA, and PG5MA) were used. The main focus was made on PEG6PG3MA hydrogel based on ethylene glycol (EG) propylene glycol (PG) pendant chains with EG (6) and PG (3) “block” units, since in the case of POPGMA and POEGMA homopolymers (i.e. hydrogels with pure PG and EG pendant chains) the VPTTs were observed far below and far above the human body temperature, respectively. Characterisation of the hydrogels was performed by swelling, UV-Vis, FTIR, SEM, DSC and in vitro biocompatibility (cytocompatibility and haemolytic activity) investigations. Due to the possibility to combine VPTT close to human body temperature with good biocompatibility, new hydrogel based on EGPG “block” pendant chains showed promising potential for different biomedical applications.

Non-isothermal degradation kinetics of virgin linear low density polyethylene (LLDPE) and biodegradable polymer blends

Abstract: The thermal degradation kinetics of several polymers, including biodegradable blends were investigated in non-isothermal thermogravimetry using several analytical methods. Virgin linear low density polyethylene (LLDPE) and LLDPE blends with polystarch-N (PSN), a prodegradant starch additive material used in 20 and 40 wt%., were investigated to determine the degradation behaviour of such materials in pyrolysis conditions. The results were compared to those obtained with virgin low (LDPE) and high density polyethylene (HDPE). An analytical solution model was also developed to assess the two degradation steps of the biodegradable blends which enabled the assessment of the apparent activation energy (Ea) of each material in the blend on its own based on the initial and final degradation temperatures. It was observed that the thermal behaviour and Ea value didn’t change significantly with the increase of biodegradable prodegradant, which shows that biodegradable blends can be treated with similar conditions regardless of the content of the biodegradable masterbatch present in the blend.

Influence of PLA stereocomplex crystals and thermal treatment temperature on the rheology and crystallization behavior of asymmetric poly(L-Lactide)/poly(D-lactide) blends

Abstract: Asymmetric poly(L-lactide)/poly(D-Lactide) (PLLA/PDLA) blends were prepared by adding small amounts of PDLA into the PLLA matrix with the formation of stereocomplex crystallites (sc-crystallites). Rheological results indicated that the PLLA/PDLA melt at lower temperatures (

Different approaches for creating nanocellular TPU foams by supercritical CO 2 foaming

Abstract: In this study, three different approaches were applied to obtain thermoplastic polyurethane (TPU) nanocellular foams. The TPU was synthesized with a 4, 4′-methylenebis (phenyl isocyanate) and 1, 4-butanediol (MDI/BD) hard segment system using a pre-polymer method. The three approaches included increasing the hard segment content, adding a graphene nucleation agent, and replacing the soft segments. Although the synthesized TPUs had a different hardness, it was possible to obtain nanocellular structures with all of the methods. The cell structure is not a function of hardness only. Crystallinity affects the cell structure as well. The addition of graphene and replacement of the soft segments were more effective at yielding nanocellular foams. Our best results showed that after adding 0.1 wt% of graphene, the average cell size of the TPU foam decreased to 715 nm, and the cell density was improved to 4.94 × 1011 cells/cm3. The relative density of the foam could be as low as 0.77. This study first reported elastomer-based nanocellular structures with such low relative density.

Novel chitosan-piperazine composite nanofiltration membranes for the desalination of brackish water and seawater

Abstract: A novel chitosan (CS)-piperazine (PIP) composite nanofiltration (NF) membrane with satisfied characteristics for brackish water and seawater desalination was successfully developed. PIP was mixed with CS during the interfacial polymerization (IP) process to enhance the NF membrane permeate flux. The resultant NF membranes were characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), atomic force microscope (AFM), contact angle. Effects of CS concentration, trimesoyl chloride (TMC) concentration, reaction time and the mixing ratio of CS/PIP on NF membrane performance were investigated thoroughly. When PIP in the aqueous phase monomers reached to 25% (w/w), the PWF (60.6 L·m−2·h−1) was synergistically improved by nearly 2 times without a significant reduction of Na2SO4 rejection (89.1%). Moreover, the NF membranes possessed excellent performance for the desalination of brackish water and seawater, which showed high potential to be applied in the desalination process for water treatment.

High performance forward osmosis cellulose acetate (CA) membrane modified by polyvinyl alcohol and polydopamine

Abstract: Cellulose acetate (CA) is a low cost and readily available material widely used in forward osmosis (FO) membranes. However, the performance of pure CA membranes is not good enough in salt separation and the traditional modification methods are generally multistep and difficult to control. In this paper, we reported high performance cellulose acetate (CA) composite forward osmosis (FO) membranes modified with polyvinyl alcohol (PVA) and polydopamine (PDA). PVA was first cross-linked onto the surface of CA membranes, and then PDA was coated with a rapid deposition method. The membranes were characterized with respect to membrane chemistry (FTIR and XPS), surface properties comprising wettability (by water contact angle), and osmosis performance. The modified membrane coated by PVA and PDA shown better hydrophilicity and exhibited 16.72 LMH osmotic water flux and 0.14 mMH reverse solute flux with DI water as feed solution and 2.0 M NaCl as draw solution and active layer facing the feed solution. This simple and highly effective modification method makes it as an excellent candidate for further exploration for FO.

PLA/ESO/MWCNT nanocomposite: a study on mechanical, thermal and electroactive shape memory properties

Abstract: In the present study, solvent casted bio-based blends of polylactic acid (PLA) and epoxidized soybean oil (ESO) were prepared at varied composition of PLA: ESO of 95:5, 90:10, 85:15, 80:20 and 75:25 wt%. The shape memory polymer (SMP) nanocomposite films of optimized PLA/ESO blend (80:20) were prepared using same solvent casting method at three different loadings (1, 3 and 5 wt%) of acid functionalized multiwalled carbon nanotubes (COOH-MWCNT). The FTIR spectra confirmed acid functionalization of MWCNT and the molecular interactions by intermolecular hydrogen bonding between PLA and ESO. Mechanical properties of the PLA, plasticized PLA with 20 wt% of ESO and its nanocomposites were investigated by tensile measurements. Thermal properties such as Tm, Tc, Tg, Xc, degradation temperature of PLA and its modified forms were studied using DSC and TGA. SEM was used to observe surface morphology of plasticized PLA. Among all, PLA + 20wt%ESO + 3wt%COOH-MWCNT shows optimum mechanical and thermal performance, which was taken to perform electroactive shape recovery test. Finally, the electroactive shape recovery of the resulting nanocomposite with 3 wt% COOH-MWCNT was investigated by a fold deploy “U”-shape bending test.

Preparation of metal-polymer nanocomposites by chemical reduction of metal ions: functions of polymer matrices

Abstract: This review summarizes the latest advances in the preparation of metal-polymer nanocomposites by chemical reduction of metal ions in polymer matrices that are classified according to their functions as stabilizing agents, templates and reducing agents. Particular attention is paid to various factors affecting the size and morphology of particles, the composition and structure of metal-polymer nanocomposites. Problems and prospects of development of metal-polymer nanocomposites obtained by chemical reduction of metal ions are considered.

Development of pH-sensitive and antibacterial gelatin/citric acid/Ag nanocomposite hydrogels with potential for biomedical applications

Abstract: This work aimed to prepare pH-sensitive and antibacterial drug releasing systems through a completely green route. To achieve this, the gelatin natural biopolymer was crosslinked with citric acid in the presence of Ag nanoparticles (NPs). Interestingly, Ag NPs formation and gelatin crosslinking were simultaneously occurred during annealing of samples without need for any toxic chemicals, which were confirmed by FTIR, UV-vis spectra, SEM and TEM observations. In addition, potential of the citric acid crosslinked-gelatin/Ag nanocomposite hydrogels was successfully explored for drug delivery applications using cefixime as a model drug. It was found that these hydrogels have pH-dependent swelling and drug release behavior with higher drug release at pH 7.4 compared to pH 1.2. Also, an antibacterial effect against the E. coli and S. aureus microorganisms was achieved by incorporation of Ag NPs into hydrogels. These hydrogels can be considered as stimuli responsive materials for oral drug delivery and wound dressing applications.

Graphene/polyethylene terephthalate nanocomposites with enhanced mechanical and thermal properties

Abstract: Nanocomposites made of poly(ethylene terephthalate) (PET) and graphene nanoplatelets (GNPs) were fabricated through micro-compounding and micro-injection molding. With an objective of improving the interactions between GNP sheets and PET chains, PET pellets were ground into a fine powder. PET pellets and powders were mixed with GNPs at 2%, 5%, 7.5%, and 10% (wt.%), molded to fabricate the nanocomposites, and then tested using several analytical characterization tools. Mechanical testing showed greater improvement through powder mixing, resulting in a 58% increase in the elastic modulus of the nanocomposites at 10% weight fraction. Thermal behavior of the nanocomposites was evaluated through differential scanning calorimetry (DSC), and it was observed that addition of GNPs into PET powders at 10% increased the crystallinity of the PET 50%. Confocal microscopy confirmed that mixing GNP with PET powders results in a more uniform distribution of the GNPs in the matrix compared to the mixture with PET pellets. X-ray diffraction (XRD) analysis confirmed the presence of GNPs with preferred orientation within the PET matrix.

Properties and phase structure of melt-processed PLA/PMMA blends

Abstract: This study examines the rheological, mechanical and thermal behavior of Poly(lactic acid)/Poly(methyl methacrylate) (PLA/PMMA) blends and takes a look at the phase structure evolution during their melt processing. Semi-crystalline or amorphous PLA grades were combined with PMMA of different molecular weight to prepare the blends. The rheological properties and phase structure was first assessed using small-amplitude oscillatory shear experiments. The blends were injection molded into bars and characterized in terms of their tensile properties and of their dynamic mechanical behavior. Differential scanning calorimetry was also used to study the miscibility and crystallization behavior of prepared blends. Tensile properties of the blends nearly followed a linear mixing rule with no detrimental effect that could have been associated with an uncompatibilized interface. However, dynamic mechanical analysis and calorimetric experiments showed that some phase separation was present in the molded parts. Nevertheless, a single Tg was found if sufficient time was given in quiescent conditions to achieve miscibility. The Gordon-Taylor equation was used to assess the polymer interactions, suggesting that miscibility is the thermodynamically stable state. The ability of PLA to crystallize was strongly restricted by the presence of PMMA and little or no crystallinity development was possible in the blends with more than 30% of PMMA. Results showed an interesting potential of these blends from an application point of view, whether they are phase separated or not.

High performance fluorinated Bismaleimide-Triazine resin with excellent dielectric properties

Abstract: A series of high performance fluorinated bismaleimide-triazine (BT) resins were prepared from 2, 2′-Bis(4-cyanatophenyl) propane (CY-1), 2′-Bis[4-(4-maleimidephenoxy) phenyl] hexafluoropropane (6FBMP) and diallyl hexafluorobisphenol A (6FDABPA). The effect of the fluorinated groups on the curing behavior, thermal stability, mechanical and dielectric properties was studied. Dielectric constant of the fluorinated BT resin was 2.89–2.94 and the dielectric loss could reach 0.002–0.004 at 1 MHz, which were dramatically improved compared with the reported cyanate ester resins. The fluorinated BT resins also exhibited excellent thermal stability, with a high glass transition temperature above 220 °C and 5% weight loss thermal decomposition temperature (Td5) exceeding 400 °C. Meanwhile, the impact strength of the fluorinated BT resins could reach 20 kJ/m2 and the flexural strength was 120 MPa. Small dipole, low polarizability, high bond energy of the carbon-fluorine (C-F) bond and symmetrical hexafluoroisopropyl group were the reason for the enhanced properties. This work suggested that the fluorinated BT resins had great potential to be used as the matrix of the advanced structural and functional composites.

Three-dimensional printing of alginate-gelatin-agar scaffolds using free-form motor assisted microsyringe extrusion system

Abstract: In current study, three-dimensional scaffolds of alginate-gelatin-agar were fabricated using free-form motor assisted microsyringe (MAM) extrusion system. Briefly, a hydrogel solution comprised of 18 wt% sodium alginate, 4 wt% gelatin, and 12 wt% agar was prepared by dissolving all components in sterile deionized water. Cubic scaffold with dimensions 9 × 9 × 9 mm3 were printed in a layer-by-layer fashion and sintered. Fourier transform infrared (FTIR) spectroscopy confirmed the chemical structure of scaffold. Field emission scanning electron microscopy (FE-SEM) analysis showed the fabrication of highly porous scaffolds with patterned structure and uniformly distributed holes at the surface. The dynamic contact angle measurement of alginate-gelatin-agar scaffold demonstrated its hydrophilic nature. The maximum tensile strength at breaking point, Young’s modulus, and elongation strain of scaffold were found to be 31.21 MPa, 0.83 GPa, and 2.51%, respectively. The scaffold supported the adhesion and growth of Hela cells. The interaction of scaffold with Escherichia coli and Saccharomyces cerevisiae as determined by the cell viability analysis through Alamar Blue assay demonstrated improved growth of microbial cells. This study can provide new dimension to the current bioprinting technology to develop patterned structure and microbes based micro/nano robots and devices.

Nanocomposite based functionalized Polyethersulfone and conjugated ternary ZnYCdO nanomaterials for the fabrication of selective Cd2+ sensor probe

Abstract: Carboxylated polyethersulfone (PES-COOH) was doped with various concentrations of ZnYCdO hybrid metal oxides on the surface of the polymer matrix to produce PES-COOH-ZnYCdO nanocomposites as a thin film. PES-COOH was fabricated by two-steps process: acetylating reaction followed by oxidation reaction, and its structure was investigated using proton nuclear magnetic resonance (1H-NMR) and Fourier-transform infrared (FT-IR) spectroscopy. Then, the fabricated PES-COOH-ZnYCdO nanocomposites (NCs) were characterized using common characterization techniques which include: scanning electron microscope (SEM), X-ray powder diffraction (XRD), FT-IR, thermal analysis, SEM with energy dispersive X-Ray (EDX) spectroscopy and transmission electron microscopy (TEM). FT-IR and XRD analysis confirmed the interactions between carboxylate ions present on the polymer surface metric and the metals that were present as ZnYCdO nanoparticles. Based on values calculated from FT-IR spectra of the PES-COOH-ZnYCdO NCs, the metals and carboxylate ions formed bindentate complexes. Also, the signal peaks of the XRD for ZnYCdO were shifted to a lower degree which also confirmed the interactions between the nanoparticles and PES-COOH. A selective Cd2+ metal ion sensor was fabricated by coating of a glassy carbon electrode (GCE) with the slurry of PES-COOH-ZnYCdO NCs polymers. The NCs assembled film onto GCE was implemented to successive detection of Cd2+ metal ion in phosphate buffer medium. To evaluate the sensor analytical performances, a calibration curve has been plotted from current versus concentration of electrolyte (Cd2+ ion). It is found linear (r2 = 0.9939) over linear dynamic range (LDR) of 0.1 nM~0.1 mM concentration of Cd2+ ion by electrochemical approach. The sensitivity and detection limit (DL) are 5.4589 μAμM−1 cm−2 and 17.39 ± 0.87 pM respectively were calculated from the slope of calibration plot. Therefore, the resultant Cd2+ sensor shows good sensitivity, reproducibility with high accuracy, wider dynamic range, short response time, very lower detection limit and long-term stability with similar performances.

Preparation of TiO2 incorporated polyacrylonitrile electrospun nanofibers for adsorption of heavy metal ions

Abstract: This paper describes the adsorption of lead and cadmium ions from an aqueous solution using a composite of titanium dioxide (TiO2)-incorporated polyacrylonitrile (PAN) electrospun nanofibers Adsorption capacities and the mechanical response of the PAN/TiO2 composite electrospun nanofibers are investigated at different weight percentages of TiO2 (05, 10, 20, and 50 wt%) The adsorption capacities of the composite PAN/TiO2 (20 and 50 wt%) for Pb(II) and Cd(II) are remarkably increased by approximately 114 and 47%, respectively, compared to those of pure PAN electrospun nanofibers Moreover, the adsorption of Pb(II) and Cd(II) by PAN/TiO2 nanofibers reaches an equilibrium within 60 min, and the process can be described using the nonlinear pseudo-second-order kinetic model The adsorption isotherm study can be represented by the Langmuir model, which suggests the homogeneous distribution of monolayer adsorptive sites on the composite nanofiber surface Furthermore, the ultimate tensile strength and ductility of all nanofiber membranes are measured through a uniaxial tension test Mechanical tests reveal a reduction in the tensile strength of the PAN/TiO2 composite nanofibers with increase in TiO2 amount due to the possible formation of agglomerates and voids in the nanofiber structure

Rotating-disk electrospinning: needleless electrospinning of poly(caprolactone), poly(lactic acid) and poly(vinyl alcohol) nanofiber mats with controlled morphology

Abstract: As a contribution to the feasibility of high-throughput electrospinning, here we report on the investigation into the production of polymer nanofiber mats through needleless electrospinning. For this study, we used poly(caprolactone) (PCL), poly(lactic acid) (PLA) and poly(vinyl alcohol) (PVA), widely used polymers in the field of electrospinning. Optimization studies were carried out to devise the characteristics of the rotating-disk electrospinning system in order to assess the processing window for each polymer. Other factors were also considered, where the production rate, fiber size distribution, and morphology of the specimens acquired by rotating-disk electrospinning and conventional electrospinning techniques were compared. Our studies also illustrate the similarities of this novel “bottom-up” process compared to the conventional one, where a high resolution image confirmed the formation of a cone-jet structure and a Taylor Cone.

Renewable eugenol-based functional polymers with self-healing and high temperature resistance properties

Abstract: A novel small molecule 1,3-bis(eugenyl) glycerol diether is synthesized from renewable eugenol and epichlorohydrin in 60% total yield, and its structure is confirmed by 1H–NMR spectrum. Then, this small molecule is utilized to prepare oligomer, linear polymer and the corresponding crosslinked polymer (denoted as P 2 ) by using thiol-ene and thiol-oxidation reactions. The polymer P 2 can form brown film on a glass substrate and can be easily put off from the substrate. Mechanical properties of P 2 show that tensile strength value is about 6 MPa, with elongation at break of around 300%. Glass transition temperature (Tg) of P 2 is −2.76 °C, meaning that P 2 is at rubber state. There are hydroxyl groups in the prepared linear polymer, which further reacts with 1,6-hexanediisocyanate (HDI) to form polyurethane P 4 with crosslinked structures. Compared with P 2 , the polyurethane P 4 forms yellow film on a glass substrate. But the film of P 4 is not so flexible as that of P 2 , presumably because of relatively higher Tg (5.85 °C) of P 4 than P 2 . Due to the existence of dynamic disulfide bonds as well as hydrogen bonds in both P 2 and P 4 , these thermoset resins show repeatable self-healing behavior stimulated by UV irradiation. Furthermore, the polyurethane P 4 exhibits ultrahigh temperature resistance performance, with Td5 = 375 °C and Td10 = 1000 °C according to TGA curve. This work is expected to expand research and potential applications of the renewable resource eugenol in preparation of smart materials.

Butanol-mediated oven-drying of nanocellulose with enhanced dehydration rate and aqueous re-dispersion

Abstract: The application potential of nanocellulose has been previously hindered by the costly and slow drying methods that this material requires, including freeze/supercritical drying process. The main issue for nanocellulose commercialization is how effectively and rapidly its high water contents (90–99%) can be removed, all of which raise its transportation and processing costs. Oven-drying is the fastest, most economical, and most scalable method for dehydrating nanocellulose, but causes strong interfibrillar aggregation and leads to poor aqueous re-dispersion. Here, we report that the problems of nanocellulose oven-drying are comprehensively overcome by adding tert-butanol (t-BuOH) to the nanocellulose solution at >90%. In a lab-scale comparison, the t-BuOH-mediated oven-drying of aqueous nanocellulose showed lower drying times by a factor of 2–12 compared to water only oven-drying and freeze drying of the same material. The dispersibility of this dried nanocellulose is as high as the never-dried material in terms of particle size, light transmittance, and sedimentation. t-BuOH reduces interfibrillar shrinkage due to the lower surface tension of t-BuOH compared to water, and a remaining t-BuOH/water mixture decreases interfibrillar adhesion and contact.

Synthesis and characterization of conjugated porous polyazomethines with excellent electrochemical energy storage performance

Abstract: Polymer based energy storage devices have luminous advantages in comparison with currently employed supercapacitors due to the environmental friendliness, cost and versatility. In general conjugated polymers are more conductive than the inorganic battery materials and have greater power capability. In this report the electron-rich conjugated polymers, containing thiophene as the core named polyazomethines ware synthesized. It contains thiophene electron-donating unit and electron withdrawing unit in which quinoxaline integrated in benzene ring. The influence of the π-linkers of the polyazomethines materials on thermal properties, and electrochemical energy storage performance was investigated. Their outstanding electrochemical performance can be attributed to their conductive frameworks, plentiful redox-active units, and homogeneous porous structure. The electrochemical properties of the polyazomethines electrode are examined with cyclic voltammetry and electrochemical impedance spectroscopy. In addition, various electrolyte solutions are studied to investigate the capacitive behavior of polyazomethines. According to the differing electrolyte types, the maximum specific capacitance of PAM-3 electrode is obtained in 1 M NaOH as 253.40 F/g.