Polypyrrole‐silk electro‐conductive composite fabric by in situ chemical polymerization

This article describes the preparation of polypyrrole‐silk composite fabric by in situ chemical polymerization of pyrrole. In situ polymerization process has been optimized by employing Box‐Behnken response surface design. The effect of process parameters on surface resistivity of the fabric has been statistically analyzed. Most significant process parameter and interaction effects have been identified. Thermal, electrical, and morphological properties of the composite fabric have been studied. Surface resistivity of the fabric obtained is 636.33 Ω. The fabric composite shows a liner V–I characteristic like an Ohmic conductor. An exponential rise of surface temperature of the fabric is observed by the application of DC voltage across it. Optical microscopic and SEM studies reveal uniform and even coating of polypyrrole on silk surface. FTIR studies indicate a possible chemical interaction between polypyrrole and silk. The polypyrrole‐treated composite fabric exhibits enhanced thermal stability as is evidenced from DSC and TGA result. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41336.     

Enhancing the electrical conductivity of carbon black/graphite nanoplatelets: Poly(ethylene‐butyl acrylate) composites by melt extrusion

The influence of processing parameters such as screw geometry, temperature profile, and screw speed on the electrical properties of hybrid composites consisting of graphite nanoplatelets and carbon black in ethyl butyl acrylate was studied. Two different screws were used to compound the hybrid composites at two different temperatures and two different screw speeds. A beneficial effect was noted with regard to the electrical properties when adding nanoplatelets to the filler system. The cause could be a synergistic effect due to the difference in particle shape of the two fillers. Lower percolation thresholds were obtained with the conventional screw due to less breakage of the graphite nanoplatelets compared to the barrier screw. No significant changes of the electrical properties were observed when changing the temperature profiles or the screw speeds. Furthermore, the melt viscosity of the compounds was not appreciably affected at the rather low filler contents used here. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42897.     

Transparency and water vapor barrier properties of polybenzoxazine‐silica nanocomposites provided with perhydropolysilazane

Poly[6,6′‐(1‐methylethylidene)bis(3,4‐dihydro‐3‐2H‐1,3‐hexylbenzoxazine)] (PB‐hda)‐silica nanocomposites were synthesized with perhydropolysilazane (PHPS) and PB‐hda by ring opening polymerization in one step. Both high transparency and good water vapor barrier property (WVP) are required to be improved in the field of packing and electronic materials, such as OLED, solar cell, and electronic paper. PB‐hda has shown high toughness and high thermal stability. However, it became dark brown and showed a reduction of WVP with increasing curing temperature, which make it difficult to be applied to packing and electronic materials. In this study, we aim to improve transparency and WVP by addition of PHPS into PB‐hda matrix. It was found that nanocomposites showed the improvement of WVP and transparency owing to Si? O? C linkages between PB‐hda and PHPS. In particular, a nanocomposite with 1 wt % of silica showed the most significant improvement in terms of transparency and the WVP. These properties were found to be influenced by the thickness of the combined polymer‐silica layers that formed around the silica particles; these layers were thickest in the 1 wt % sample. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44238.     

Fluorescence turn‐on chemical sensor based on water‐soluble conjugated polymer/single‐walled carbon nanotube composite

A chemical sensor for methyl viologen (MV²⁺), based on a water‐soluble conjugated polymer/single‐walled carbon‐nanotube (SWNT) composite, was fabricated. Water‐soluble poly(m‐phenylene ethynylene) with sulfonic acid side‐chain groups (mPPE‐SO₃) was synthesized via a Pd‐catalyzed Sonogashira coupling reaction and used to prepare a highly stable mPPE‐SO₃/SWNT composite with strong π–π interactions in water. The relationship between the optical properties and sensing capability of the mPPE‐SO₃/SWNT composite in aqueous solution was investigated. The addition of MV²⁺ enhanced the fluorescence intensity of the mPPE‐SO₃/SWNT composite by inducing a conformational change of the polymer from a helical to a random‐coil structure. The water‐soluble mPPE‐SO₃/SWNT composite enabled highly sensitive fluorescence detection of MV²⁺ in aqueous solutions with no precipitation resulting from reaggregation of the SWNTs. This mPPE‐SO₃/SWNT composite sensor system is therefore an effective turn‐on chemical sensor for MV²⁺. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43301.     

Effect of microstructure on the dielectric properties of poly(vinyl alcohol)–poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonate) composite films

Poly(3,4‐ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT–PSS) was blended with poly(vinyl alcohol) (PVA) to form 0, 10, 20, 30, 40, and 50 vol % PEDOT–PSS/PVA solutions, and their freestanding films were prepared with a simple and cost‐effective solution casting technique at 27 °C in the absence of additives. Field emission scanning electron microscopy images revealed changes in the cocontinuous network to a rodlike morphology in the composite films from 10 to 50 vol % PEDOT–PSS/PVA. The alternating‐current conductivity was found to obey Jonscher's power law. The obtained values of the dielectric constant at 27 °C were relatively high, and a maximum value of 6.7 × 10⁴ at 100 Hz for 40 vol % PEDOT–PSS'/PVA was observed. The dielectric loss attained a maximum value of about 10⁶ at 100 Hz for 40 vol % PEDOT–PSS/PVA. However, a decrease in the dielectric parameters was observed at 50 vol % PEDOT–PSS/PVA because of locally induced strain in the microstructure. The variations in polarization with respect to the applied electric field (P–E) were determined for 50, 100, and 500 Hz at 500 V for the freestanding composite films of lower concentrations up to 20 vol % PEDOT–PSS/PVA. In summary, the dielectric and P–E measurements confirmed that the electrical characteristics changed in accordance to the contribution from both resistive and capacitive sites in the PEDOT–PSS/PVA composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45079.     

Magnetic‐field‐assisted electrospinning highly aligned composite nanofibers containing well‐aligned multiwalled carbon nanotubes

Composite nanofiber meshes of well‐aligned polyacrylonitrile (PAN)/polyvinylpyrrolidone (PVP) nanofibers containing multiwalled carbon nanotubes (MWCNTs) were successfully fabricated by a magnetic‐field‐assisted electrospinning (MFAES) technology, which was confirmed to be a favorable method for preparation of aligned composite nanofibers in this article. The MFAES experiments showed that the diameters of composite nanofibers decreased first and then increased with the increase of voltage and MWCNTs content. With the increase of voltage, the degree of alignment of the composite nanofibers decreased, whereas it increased with increasing MWCNTs concentration. Transmission electron microscopy observation showed that MWCNTs were parallel and oriented along the axes of the nanofibers under the low concentration. A maximum enhancement of 178% in tensile strength was manifested by adding 2 wt % MWCNTs in well‐aligned composite nanofibers. In addition, the storage modulus of PAN/PVP/MWCNTs composite nanofibers was significantly higher than that of the PAN/PVP nanofibers. Besides, due to the highly ordered alignment structure, the composite nanofiber meshes showed large anisotropic surface resistance, that is, the surface resistance of the composite nanofiber films along the fiber axis was about 10 times smaller than that perpendicular to the axis direction. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41995.     

Improved electrochemical performances of polyaniline by graphitized mesoporus carbon: Hybrid electrode for supercapacitor

In this work, graphitized mesoporus carbon (GMC) was used to increase the specific capacitance and cycle stability of polyaniline (PANI). Hybrid material of polyaniline‐graphitized mesoporus carbon (GMCP) was prepared by in situ chemical polymerization of aniline in presence of sulphuric acid using ammonium persulfate oxidant with various amounts of GMC. Formation of hybrid sample was confirmed from X‐ray diffraction, and the composite sample was stable up to 250°C. Morphology, crystalline nature, and electrochemical performance of GMCP were compared with that of its individual components, GMC and PANI. GMC showed particle morphology and PANI showed nanofiber morphology. GMCP2 composite showed nanofibrous form of PANI grown on GMC (spherical form) along with PANI nanofibers. Higher crystallinity was obtained for GMCP than that of PANI. Cycling stability of GMCP2 was carried up to 12,000 cycles at 1200 W kg^?1 and the retention capacitance was 66% of its original capacitance of 243 F g^?1. With the same power density, GMC showed less capacitance value of 53 F g^?1 with 92% retention and PANI showed capacitance of 187 F g^?1 and it underwent 1500 cycles only. Higher supercapacitor performance was obtained for GMCP composite compared to that of its components, PANI and GMC. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42540.     

Chemical polymerization of pyrrole in the presence of l‐serine or l‐glutamic acid: Electrically controlled amoxicillin release from composite hydrogel

Polypyrrole (PPy) was chemically prepared from aqueous solutions individually containing l ‐serine or l ‐glutamic acid, with the addition of ammonium persulfate as the oxidant. The electrical, XPS and FTIR characterizations indicated that the amino acids co‐doped the PPy backbone. TEM revealed that PPy presented a quasi‐spherical morphology with diameters in nanometric scale. The nanostructures of PPy‐glutamic acid efficiently adsorbed therapeutic doses of amoxicillin. Composite hydrogels were obtained by the entrapment of amoxicillin‐loaded PPy in polyacrylamide network. The antibiotic molecules can be subsequently released (or sustained) from composite hydrogel in response to application (or removal) of electrical stimulation. This tuning release profile can lead to promising drug delivery applications such as implantable devices and iontophoretic systems. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41804.     

Electrokinetic and antibacterial properties of needle like‐TiO2/polyrhodanine core/shell hybrid nanostructures

The aim of this study was to fabricate needle like‐TiO₂/polyrhodanine nanostructures by polymerizing rhodanine monomer on the TiO₂ nanoparticles' surfaces and investigate their antibacterial activities. The structural, thermal, morphological, surface and electrical properties of non‐covalently functionalized nanoparticles were characterized by using FTIR, XPS, elemental analysis, TGA, XRD, SEM‐EDX, TEM, contact angle, and conductivity measurements. Characterization results confirmed the formation of needle like‐TiO₂/polyrhodanine (PRh) core/shell hybrid nanostructures. Alterations on the surface and electrokinetic properties of the materials were characterized by zeta (ζ)‐potential measurements with the presence of various salts and surfactants. The ζ‐potential of needle like‐TiO₂ was observed to increase from ?7.6 mV to +28.4 mV after forming a core/shell needle like‐TiO₂/PRh nanocomposite structure and with the presence of cetyltrimethyl ammonium bromide (CTAB) surfactant. Thereby colloidally more stable dispersions were formed. Antibacterial properties of needle like‐TiO₂/PRh were also tested against Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli by various methods and they showed good antibacterial activity. The highest killing efficiency was determined for needle like‐TiO₂/PRh against E. coli by colony‐counting method as 0.95. TEM experiments also showed the immobilizations of the nanoparticles on E. coli and revealed the interactions between E. coli and the nanoparticles. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41554.     

Structure and morphology of nanoporous zno and dark current‐Voltage characteristics of the glass/(TCO)/zno/poly[2,7‐(9,9‐dioctylfluorene)‐alt‐(5,5'‐bithiophene)/ag structure

The hybrid organic‐inorganic structure based on glass/(TCO)/nanoporous ZnO/poly[2,7‐(9,9‐dioctylfluorene)‐alt‐(5,5′‐bithiophene)]/Ag that was prepared by physical deposition has been investigated. The structure of the nanostructured ZnO obtained by magnetron sputtering was confirmed by X‐ray diffractometry (XRD) and energy dispersive X‐ray spectroscopy (EDX). Scanning electron microscopy (SEM) analysis proved the existence of short and interconnected zinc oxide (ZnO) fibers, which form a continuous porous network with pores having an average diameter of 100 nm. Current‐voltage (I‐V) curves of the glass/TCO/ZnO/PF‐BT/Ag hybrid structure are similar to those of typical p‐n junctions and stable until 90°C temperature. According to the I‐V characteristics, the dominant mechanism of current flow is based on the generation‐recombination of carriers in the depletion region at low direct biases and also on the injection of carriers at high biases. The reverse branch of the I‐V characteristic, calculated in log‐log scale, shows one segment with a power coefficient of 3/2 at room temperature. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42415.     

NIR-responsive Fe3O4@PPy nanocomposite for efficient potential use in photothermal therapy

In this work, superparamagnetic Fe₃O₄@PPy nanocomposite with core-shell structure having strong near-infrared (NIR) absorption is synthesized via a facile two-step modified procedure. The prepared nanocomposite samples are characterized by UV–vis, FTIR, SEM, TEM, VSM, and XRD. The effects of laser power density (1.5–2.5 W cm⁻²) and aqueous concentration (0.01–0.2 mg ml⁻¹) of the nanocomposite on the photothermal performance are investigated in the NIR region (808 nm). At 0.1 mg ml⁻¹ concentration, the temperature reaches up to 50.1°C, 64.1°C, and 78.4°C within 10 min, under 1.5 W cm⁻², 2.0 W cm⁻², and 2.5 W cm⁻² NIR laser power density values, respectively. Photothermal conservation efficiency is calculated as 43.9% and the nanocomposite exhibits excellent photothermal stability. In summary, the core-shell Fe₃O₄@PPy nanocomposite is a promising candidate for photothermal therapy and simultaneous magnetic field-guided treatments.     

Sensing and surface morphological properties of a poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐bithiophene] liquid‐crystalline polymer for optoelectronic applications

The sensing properties of a poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐co‐bithiophene] (F8T2) polymer were investigated at different concentrations and volume percentages. The effects of the concentrations and volume percentages on the sensing parameters were investigated. The sensitivities of F8T2 were found to be 3.190, 1.434, and 0.362 dB/vol % at 290, 580, and 940 nm, respectively. The response of the F8T2 increased with increasing concentration. F8T2 exhibited good sensitivity and response behaviors. Then, the optical parameters based on the refractive indices of the F8T2 at different molarities were calculated. The dispersion energy, moment of the dielectric constant optical spectrum (M_?1, M_?3), oscillator strength, and contrast of the F8T2 increased with increasing molarity, whereas the average excitation energy or single‐oscillator energy decreased with increasing molarity. The surface morphological properties of the F8T2 polymer film were investigated, and the roughness parameters were obtained. The F8T2 polymer could be used in the fabrication of various sensors because of the good solubility, sensitivity, and response behaviors. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41659.     

Polyaniline nanofibers for In situ MAO‐catalyzed polymerization of ethylene

In this work electro‐conductive polyaniline nanofibers (PAni‐nanofibers) were prepared via interfacial methodology. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations revealed that the synthesized PAni‐nanofibers present high aspect ratio with an average diameter of 80 nm, while they exhibit high conductivity (DC conductivity values: 4.19 ± 0.21 S cm^?1). After specific treatment to remove moisture and remaining trapped HCl from PAni‐nanofibers, it was possible to prepare promising polyethylene (PE)/PAni composites by in situ polymerization of ethylene using bis(cyclopentadienyl) zirconium(IV) dichloride (Cp₂ZrCl₂) and methylaluminoxane (MAO) as catalytic system. More precisely, various contents of PAni‐nanofibers (from 0.2 to 7 wt %) were successfully incorporated in the in situ produced PE/PAni nanocomposites. PAni‐nanofibers were found to affect significantly the crystallization of the polyolefinic matrix while preserving its thermal stability. Preliminary measurements of electric properties showed PAni‐nanofibres are able to bring electro‐conductive properties to the in situ polymerized PE/PAni composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41197.     

Electrochemical behavior of a Nafion‐membrane‐based solid‐state supercapacitor with a graphene oxide—multiwalled carbon nanotube—polypyrrole nanocomposite

In this study, we sprayed a graphene oxide–multiwalled carbon nanotube (GM) suspension in isopropyl alcohol–water onto a Nafion membrane. The electrodeposition of polypyrrole (PPy) was carried out on Nafion to complete the fabrication of a solid‐state symmetric supercapacitor. Nafion 117 membranes are used as electrolyte separators in the preparation of supercapacitors. The characterization of the symmetric supercapacitor was done by X‐ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The electrochemical properties of the symmetric solid‐state supercapacitor were investigated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques in 1M lithium chloride. A specific capacitance of 90.4 mF/cm² (258.3 F/g¹) was obtained for the supercapacitor at a scan rate of 10 mV s^?1. Maximum energy and power densities of 10 W h/kg and 6031 W/kg were obtained for the fabricated supercapacitor. In such a symmetric configuration, the highly interconnection networks of GM–PPy provided good structure for the supercapacitor electrode, and the good interaction between PPy and GM provided fast electron‐ and charge‐transportation paths so that a high capacitance was achieved. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44926.     

In situ fabrication of polyaniline‐silver nanocomposites using soft template of sodium alginate

Polyaniline (PANI)‐Ag nanocomposites were synthesized by in situ chemical polymerization approach using ammonium persulfate and silver nitrate as oxidant. Characterizations of nanocomposites were done by ultraviolet–visible ( UV–vis), Fourier transform infrared (FTIR), X‐ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy (TEM). UV–vis, XRD and FTIR analysis established the formation of PANI/Ag nanocomposites and face‐centered‐cubic phase of silver. PANInanofibers were of average diameter ～ 30 nm and several micrometers in length. Morphological analysis showed that the spherical‐shaped silver nanoparticles decorate the surface of PANI nanofibers. Silver nanoparticles of average diameter ～ 5–10 nm were observed on the TEM images for the PANI‐Ag nanocomposites. Such type of PANI‐Ag nanocomposites can be used as bistable switches as well as memory devices. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and characterization of s‐histidine‐derived poly (ionic liquid)/silica nanocomposites and their application in the enantioselective hydrolysis of a chiral ester

In this study, a new optically active monomer containing two chemically preformed imide rings was synthesized. The monomer was then used to synthesize optically active poly(amide imide)s (OAPAIs) and an optically active polyionic liquid (OAPIL), which were finally reacted with various amounts of silica nanoparticles in an in situ polymerization reaction to produce OAPAI/SiO₂ and OAPIL/SiO₂ hybrid materials containing sulfonic acid groups. The prepared monomers and the OAPAI and OAPIL nanocomposites were characterized by ¹H‐NMR spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, X‐ray diffraction, scanning electron microscopy, X‐ray photoelectron spectroscopy, and differential scanning calorimetry. OAPIL/SiO₂ served as an excellent catalyst in water as a solvent for the hydrolysis of d ,l ‐phenylglycine methyl ester with the advantage of a markedly enhanced enantioselectivity and activity. Also, the enantioselectivity was strongly dependent on the SiO₂ content in the OAPIL/SiO₂ systems; a favorable SiO₂ content was 20% (w/w). The enantioselectivity was 95.2% (substrate conversion = 62.3%). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39595.     

Electrochemical synthesis of nanostructured polyaniline: Heat treatment and synergistic effect of simultaneous dual doping

Different nanostructured polyaniline (PAni) has been synthesized via facile template‐free electrochemical synthesis approach in aqueous medium. Instead of conventionally used aniline, aniline sulphate was used in electrochemical polymerization. The synthesis process involves simultaneous doping with combination of inorganic and organic acid, i.e., sulfuric acid (H₂SO₄) and p‐toluenesulfonic acid (PTSA) at different ratios keeping total dopant concentration constant. Synergistic increase in conductivity is observed and the best conductivity is achieved at 3:1 ratio of [H₂SO₄]:[PTSA]. Different nanostructures of PAni are revealed through morphological analysis consisting of nanosphere, nanorod, and clustered particles among which finer nanorods show the best electrical conductivity. Upon controlled heat treatment followed by further cooling, resistivity increases, but after one day it decreases again and in the optimized dual doped PAni, it approaches approximately the same value of initial resistance. Lattice strain and benzenoid to quinonoid ratio increases with heat treatment. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Measurements of size distribution nanoparticles in ultraviolet‐curable methacrylate‐based boehmite nanocomposites

A deep study on the possibility to increase the quality of the dispersion of organically modified Boehmite nanoparticles into photo‐polymerizable methacrylic‐siloxane monomers, to be used as coatings, was conducted using unconventional indirect analyses. The nanocomposite were produced using two different procedures, starting from the conventional “solvent dispersion method.” The two procedures used differ for the technique used to obtain the dispersion of Boehmite, i.e., sonication or magnetic stirring and for the time used in each procedure. The efficiency of each method of preparation of nanostructured systems was analyzed, both in the liquid (uncured) and ultraviolet (UV) cured state. First, dynamic light scattering and rheological measurements were performed on the liquid suspensions, supplying experimental data used in proper theoretical models to estimate the dimensions and distribution of Boehmite particles. The suspensions obtained with the two different methods were, then, UV cured obtaining thin and thick films, on which scanning electron microscopy and transmittance measurements were performed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of unfunctionalized and HNO3‐functionalized MWCNT on the mechanical and electrical performances of PEMFC bipolar plates

This study aims at developing lightweight and high performance electrically conductive nanocomposites for proton exchange membrane fuel cell (PEMFC) bipolar plates (BPPs). These composites were made from an optimized co‐continuous mixture of Polyethylene terephthalate (PET) and polyvinylidene fluoride (PVDF) reinforced with highly conductive carbon additives composed of carbon black (CB) and synthetic graphite (GR). Multiwall carbon nanotubes (MWCNT) were functionalized then used to improve BPPs electrical conductivity and their mechanical properties, such as flexural and impact strengths. It was observed that the best BPP prototype was obtained using nitric acid (HNO₃)‐functionalized MWCNT. The latter led to the smothest BPP surface, the lowest through‐plane resitivity (0.12 Ω cm) and the highest impact and flexural strengths. These results are attributed to the improved dispersion of the functionalized MWCNT, a result of their best compatibilization with the (PET/PVDF) polymeric phase. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43624.     

Morphology control of conducting polypyrrole nanostructures via operational conditions in the emulsion polymerization

Polypyrrole (PPy) nanostructures with diameter smaller than 100 nm were synthesized by chemical oxidative polymerization of pyrrole in the presence of cetyl trimethylammonium bromide and sodium dodecyl sulfate as surfactants. Hydrochloric acid was used as dopant, and a solution of potassium peroxydisulfate was used as initiator. The influence of polymerization temperature, feeding strategy, and the type of surfactant on the morphology and conductivity of PPy nanostructures were investigated and well‐described. A simple route just via controlling the operational conditions in the emulsion polymerization is reported to obtain nanostructured PPy with desirable morphology and relatively good conductivity. The analysis results demonstrated that the conductivity of samples is highly affected by their morphology whereas PPy nanofibers exhibited higher conductivity respecting the other morphologies (0.66 S/cm). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44697.