Content Of Polar Groups Research Articles

Study on the epoxy bonding properties of polyphenylene sulfide matrix composites reinforced by montmorillonite and basalt fiber

To improve the epoxy bonding properties of polyphenylene sulfide (PPS) matrix composites, CK-MMT and K-BF were prepared by modifying montmorillonite (MMT) and basalt fiber (BF) with cetyl trimethyl ammonium bromide (CTAB) and 3-Glycidyloxypropyltrimethoxysilane (KH-560) as the modifiers. CK-MMT/BF/TPU/PPS composites were prepared by injection moulding. The surface properties of the composites were tested and characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), etc. The epoxy bonding and mechanical properties were studied by combining the single-lap-joint tensile shear strength test and notched impact test. The results demonstrated the successful preparation of the modified MMT and BF. With the addition of CK-MMT and K-BF in different ratios, the surface roughness and the contents of polar groups of the composites increased, which could effectively improve the epoxy bonding properties of PPS matrix composites. When the additions of CK-MMT and K-BF were 10 and 25 wt%, respectively, the composites had the best overall properties. It demonstrated a single-lap-joint tensile shear strength was 7.56 MPa, representing a 220.34% increase over that of thermoplastic polyurethane/polyphenylene sulfide (TPU/PPS) and a 477.10% increase over that of pure PPS.

Regulation and characterization of polar groups on the surfaces of cellulose nanocrystal–nanosilver hybrids

Cellulose nanocrystals (CNCs) with a high content of polar groups were prepared via the oxidation process by controlling the amount of mixed acid, incorporating additional additive of citric acid and vitamin C as active agents, and applying ultrasonic crosslinking. Subsequently, cellulose nanocrystal–silver (CNC–Ag) nanohybrid materials were synthesized via an oxidation hydrolysis reaction, which displayed good dispersibility and high interaction, leading to the hydrogen bonding between polar groups (-OH and -COOH) on the surface of CAC–Ag nanohybrids. The positive effects of hydrogen bonding on the surface of CAC–Ag nanohybrids were confirmed by the high carboxyl group content (2.69 mmol/g) and low contact angle (53.7°) tested. In addition, CAC–Ag nanohybrids showed significant antibacterial activity against both Gram-negative E. coli and Gram-positive S. aureus. These results showed that the high-performance CNC–Ag nanohybrids prepared in this study may be highly suitable as nano-fillers for polyester materials used in antibacterial food packaging.

Effect of Polar Hydrocarbon Contents on Oil-Water Interfacial Tension and Implications for Recent Observations in Smart Water Flooding Oil Recovery Schemes.

For decades now, low salinity water flooding (LSWF) oil recovery has emerged as an environmentally benign and cost-effective method for improved oil recovery, where research findings have reported pH and interfacial tension effects. Considering the effect of oil chemistry on interfacial tension and the potential of this chemistry to have a direct relationship with LSWF, we measured the interfacial tension of four crude oils with composition varying from those of conventional to unconventional ones. We also characterized the crude oil samples using infrared spectroscopy and a wet chemistry method based on asphaltene precipitation. Our research approach has enabled us to relate the composition of crude oil to the interfacial tension trend at pH encountered in improved oil recovery schemes. Our research methodology, based on an integrated approach to using infrared spectroscopy and interfacial tensiometry, has also enabled us to propose a more robust theoretical explanation for current observations in LSWF related to pH and interfacial tension. In this regard, oil-water interfacial tension depends on the concentration of polar components, such that the higher the concentration of polar groups in crude oil, the higher the interfacial tension at a given pH of aqueous solution. We have also shown that the acid-base behavior of polar groups at the oil-water interface provides a theoretical interpretation of the explicit relationship between oil-water interfacial tension and the electrostatic components of interfacial tension as given by the energy additivity theory.

Adsorption behaviour and mechanism of Avermectin-based pesticides in soil driven by H-bonds formed between the compounds and humus

Adsorption is an essential process in regulating pesticide distribution in soil. However, the relationship between soil adsorption mechanisms and the structure of the compounds is unclear. Different soil samples (S1, S2, S3) were selected for adsorption tests of avermectin B2a (AVB2a), avermectin B1a (AVB1a), and emamectin benzoate (EB) to investigate the influence of adsorbent properties and compound structure on the adsorption. The adsorption of the three chemicals by the three soils was extensive and irreversible. Soil adsorption of AVB2a was strongest, followed by AVB1a and EB. Soil adsorption tests of three avermectin-based pesticides showed that the –OH groups of the compounds were the main adsorption site. The humus fraction, a significant component of the soil organic matter, was extracted for further adsorption tests on the compounds. The humus fraction most strongly adsorbs AVB2a, followed by AVB1a and EB, indicating that –OH is also the main site for the humus fraction to adsorb compounds. Differences in the content of polar groups in the humus fraction by elemental analysis and 13C NMR analysis suggested that the –OH of avermectin-based pesticides interacts with the polar groups of humus. Quantum chemical calculations confirm that the –OH groups of the compound form hydrogen bonds with amino, hydroxyl, carboxyl, and carbonyl groups in the humus, thus demonstrating that hydrogen bonding is the mechanism by which avermectin-based pesticides are adsorbed to the soil.

Effect of the polar group content on the glass transition temperature of ROMP copolymers.

Polar groups have long been recognized to greatly influence the glass transition temperature (Tg) of polymers, but understanding the underlying physical mechanism remains a challenge. Here, we study the glass formation of ring-opening metathesis polymerization (ROMP) copolymers containing polar groups by employing all-atom molecular dynamics simulations. We show that although the number of hydrogen bonds (NHB) and the cohesive energy density increase linearly as the content of polar groups (fpol) increases, the Tg of ROMP copolymers increases with the increase of fpol in a nonlinear fashion, and tends to plateau for sufficiently high fpol. Importantly, we find that the increase rate of Gibbs free energy for HB breaking gradually slows down with the increase of fpol, indicating that the HB is gradually stabilized. Therefore, Tg is jointly determined by NHB and the strength of HBs in the system, while the latter dominates. Although NHB increases linearly with increasing fpol, the HB strength increases slowly with increasing fpol, which leads to a decreasing rate of increase in Tg.

High‐Permittivity Polysiloxanes for Solvent‐Free Fabrication of Dielectric Elastomer Actuators

AbstractDielectric elastomer actuators (DEAs) are a class of soft transducers with broad potential applications in soft robotics. DEAs consist of two stretchable electrodes on a dielectric elastomer, which deform and generate force when charged. The generated force is increased by placing many DEAs on top of one another to form a stack actuator. Next‐generation stack actuators require high permittivity inks that are solvent‐free processable and cross‐linkable into thin elastic films. Here, a process toward elastomers with tuneable permittivity that can be prepared solvent‐free is reported. Polycondensation of chlorosilanes yields polymers with vinyl end‐groups and cross‐linkers with multiple hydrosilane groups that both carry polar chloromethyl groups. Their dielectric permittivity and mechanical properties are tuned by changing the polar group content and the molar mass of the vinyl‐terminated polymer, respectively. Solvent‐free doctor blading provides thin films, which are cross‐linked by heating. DEAs prepared from the films reach a lateral actuation of promising 4.6% at a low electric field of 11.2 V µm‐1 and can be operated at frequencies up to 5 Hz. The high‐permittivity polymer ink is used in a solvent‐free layer‐by‐layer stack actuator fabrication, which yields an actuator with three active layers that gives a thickness strain of 1.0% at 12.4 V µm‐1.

Self-Healable, Self-Repairable, and Recyclable Electrically Responsive Artificial Muscles.

Elastomers with high dielectric permittivity that self‐heal after electric breakdown and mechanical damage are important in the emerging field of artificial muscles. Here, a one‐step process toward self‐healable, silicone‐based elastomers with large and tunable permittivity is reported. Anionic ring‐opening polymerization of cyanopropyl‐substituted cyclic siloxanes yields elastomers with polar side chains. The equilibrated product is composed of networks, linear chains, and cyclic compounds. The ratio between the components varies with temperature and allows realizing materials with largely different properties. The silanolate end groups remain active, which is the key to self‐healing. Elastomeric behavior is observed at room temperature, while viscous flow dominates at higher temperatures (typically 80 °C). The elasticity is essential for reversible actuation and the thermoreversible softening allows for self‐healing and recycling. The dielectric permittivity can be increased to a maximum value of 18.1 by varying the polar group content. Single‐layer actuators show 3.8% lateral actuation at 5.2 V µm–1 and self‐repair after a breakdown, while damaged ones can be recycled integrally. Stack actuators reach an actuation strain of 5.4 ± 0.2% at electric fields as low as 3.2 V µm–1 and are therefore promising for applications as artificial muscles in soft robotics.

Preparation and properties of UV-curable waterborne silicon-containing polyurethane acrylate emulsion

The non-toxic and environmental protection characteristics of water-based coating make it has a good development prospect, but its poor water resistance and stability have attracted widespread attention. A type silicon-containing polyurethane acrylate core-shell structure emulsion was prepared by using in-situ self-emulsification, and it was applied to fabric-based substrates to study the influence of the different distribution of groups on the surface of the coating on the interfacial properties of the fabric-based coating. The silicon-containing polyurethane acrylate was synthesized by grafting unsaturated double bond with silane coupling agent which was characterized by FTIR and 1H NMR. The stability of the emulsion was tested by dynamic light scattering technique. The distribution of latex particles and the core-shell structure were observed by transmission electron microscopy (TEM). After the introduction of vinylsiloxane, the particle size of polyurethane acrylate emulsion decreased from 180.3 nm to 111.7 nm, and the emulsion samples could be stored for 6 months stably. The surface properties and morphology of the cured polyurethane acrylate film samples were evaluated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The thermal stability of cured film was analyzed by thermogravimetry (TG). In addition, emulsion samples with different silicone contents were coated on different fabric-based substrates (cotton fiber, PET and PP), and the fabric based coatings were cured quickly by utilizing the characteristics of fast UV curing and low energy consumption. The low surface energy organosiloxane was easier to migrate to the surface of the material, which increased the surface tension of the fabric based coatings. The water contact angles of the coatings interface were greater than 100°, showed good hydrophobic performance. In addition, the emulsion was dipped into the fabric-based substrate and it was found that the content of polar groups (-COO−) on the surface of the fabric-based coatings gradually increases along with increase of the concentration of the emulsion and the number of dips, and the organosiloxane originally on the surface of the coating was coated on the inner layer, made the hydrophobic performance of the coating decreased and when the emulsion concentration increased to 0.5 g/mL or the dip coating reached 5 layers, the interfacial performance of the coating changed from hydrophobic to hydrophilic. And the fabric based coatings with adjustable interfacial properties were obtained.

High toughness, thermal resistance and excellent dielectric properties phenolic epoxy vinyl ester resin modified by hyperbranched polyimide

PurposePhenolic epoxy vinyl ester resin (PEVER) is an advanced resin matrix, which has excellent heat resistance, electrical insulation. However, the brittleness and poor toughness of its curing product limited its application, so this paper aims to modify the PEVER with hyperbranched polyimide (HBPI), so as to enhance the toughness, heat resistance and dielectric properties of PEVER.Design/methodology/approachHexamethylene diisocyanate trimer was used as the central reactant. Methyl tetrahydrophthalic anhydride was used as the branching unit, stannous octoate was used as the catalyst and hydroquinone was prepared as the inhibitor. Then, the hyperbranched structure of HBPI was characterized by Fourier transform infrared spectrometer and 13C-NMR. Next, PEVER was mixed with different contents of HBPI, and then the authors tested its curing product.FindingsIt is found that with the addition of HBPI, the free volume of the system was increased and the content of polar groups was decreased in each unit space, so the dielectric constant (ε) and the dielectric loss (tanδ) were decreased. In addition, PEVER could be well toughened by HBPI and the thermal stability of PEVER was improved.Originality/valueHBPI has excellent heat resistance. The addition of hyperbranched polymer increases the free volume of the system so it can slow down the transfer of stress and its nearly circular structure can absorb the impact energy from all directions. Moreover, an appropriate amount of free volume can decrease the dielectric constant of PEVER by reducing the content of polar groups.

The non-linear effect of oil polarity on the efficiency of low salinity waterflooding: A pore-level investigation

Oil polarity is an important property impacting the efficiency of low salinity waterflooding (LSWF). It directly affects fluid/fluid and rock/fluid interactions, controlling the interfacial properties and forces. However, the current findings in the literature on the effect of concentration of polar components on oil recovery by LSWF are contradictory. Therefore, the main objective of this paper is to investigate how the type of non-polar fractions and the concentration of acidic polar oil constituents change the trapped oil saturation at the pore-scale during LSWF. In this regard, we conducted a series of microfluidics LSWF experiments in both secondary and tertiary modes, using clay-free glass micromodels of representative elementary volume (REV) size. Both model oils and crude oil were tested. The polarity of model oils was manipulated by introducing different amounts of oleic acid into the samples. In addition, the contact angle under dynamic salinity alteration (CA-DSA), interfacial tension (IFT), and oil/brine zeta-potential were measured as a function of oil polarity for a detailed understanding of the pore-scale results.Based on the results, polar acidic fraction increases both the oil-wetting tendency under high salinity (HS) condition and the degree of wettability alteration under low salinity (LS) condition. Increasing the concentration of the polar components in the model oils resulted in reducing oil/brine IFT by 7–9 mN/m in HS and 8–12 mN/m in LS. As the IFT was reduced, the sweep efficiency of both HS and LS flooding was improved, which can be ascribed to the reduction of capillary trapping. However, the change of IFT by change of salinity was minor; thus, it cannot be considered a primary mechanism of LSWF. The ultimate oil recovery from HS and LS injection steps was highest when crude oil was used than using the most polar model oil. In the absence of polar components, no incremental oil recovery during LSWF was observed regardless of the molecular weight of the model oil. The efficiency of LSWF with all the polar oils was higher in the secondary injection than in the tertiary mode, as also reported in core-scale studies.The main novel insight from the study is that the oil recovery factor by LSWF is logarithmically correlated with the oil polarity. The measured zeta-potential at the oil/brine interface also confirms a logarithmic correlation between the oil/brine interface potential and the concentration of polar components in the oil samples. This highlights that the bulk concentration of polar groups and their respective concentration at the oil/brine interface are not linearly related. Therefore, the acid number alone cannot predict the concentration of polar components at the interface and is not recommended to be used for screening potent oils.

Polysiloxanes Modified with Different Types and Contents of Polar Groups: Synthesis, Structure, and Thermal and Dielectric Properties

Polysiloxanes Modified with Different Types and Contents of Polar Groups: Synthesis, Structure, and Thermal and Dielectric Properties

Effect of 2-MeIM/Zn Molar Ratio on CO2 Permeability of Pebax/ZIF-8 Mixed Matrix Membranes

The impact of controlling molar ratio of ZIF-8 precursors on Pebax 1657 and Pebax 2533 based Mixed Matrix Membranes (MMMs) on the CO2 permeability and CO2 /N2 ideal selectivity was investigated. Three types of ZIF-8 were synthesized by controlling molar ratio of 2-methylimidazole and zinc nitrate hexahydrate as 2/1, 8/1, and 32/1. The SEM images and XRD patterns of ZIF-8 showed that particle sizes and crystallinity peaks were decreased as molar ratio of ZIF-8 increased. The CO2 permeability of Pebax MMM was improved by filling with the ZIF-8 particles compared to the pure Pebax. At equivalent temperatures, the highest CO2 permeability was shown in Pebax 1657/ZIF-8 with the ZIF8 precursors’ molar ratio of 32/1 and Pebax 2533/ZIF-8 with the molar ratio of 2/1. As molar ratio of ZIF-8 precursors increases, CO2 permeability of Pebax 1657 was increased by excessive sorption of CO2 by imidazolium ions in ZIF-8, whereas CO2 permeability of Pebax 2533 was decreased by decreasing pore size and particle size of ZIF-8. The CO2 permeability was higher in Pebax 2533/ZIF-8 compared to Pebax 1657/ZIF-8, because Pebax 2533 has more concentrations of polar groups in the polymer matrix than Pebax 1657. However, the CO2 /N2 ideal selectivity was higher in Pebax 1657/ZIF-8 compared to Pebax 2533/ZIF-8 because diffusivity of Pebax 1657 compared to Pebax 2533 is lower for nonpolar gases, such as N2 , and the solubility is higher for polarizable gases like CO2 . As increasing temperature, Pebax/ZIF-8 MMMs showed enhancement of CO2 and N2 permeability but decreased in CO2 /N2 ideal selectivity.

Potassium phosphate/magnesium oxide modified biochars: Interfacial chemical behaviours and Pb binding performance

Removal of lead (Pb) from aqueous solutions by biochar is a promising method. In this study, wheat straw biochar (WBC) was modified by phosphate/magnesium via pre-treatment of biomass and post-treatment of biochar, noting as WBC_PMA and WBC_PMB, respectively. Based on Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses, phosphate/magnesium chemically bound to the structures of biochar surface, increasing the contents of polar groups (i.e., -COOH and -OH) and phosphorus-containing compounds, mainly Mg3(PO4)2 and Mg2P2O7. Owing to pyrolysis process enhancing loading ability of phosphate/magnesium, WBC_PMA possessed more active functional groups than WBC_PMB. Results showed that maximum sorption capacity of Pb was improved by modifications, following the sequence of WBC_PMA (470.09 mg/g) > WBC_PMB (308.39 mg/g) > WBC (59.93 mg/g). Pseudo-second-order kinetics and thermodynamics study indicated that chemisorption was involved in sorption process. Precipitation, complexation and cation exchange dominated Pb sorption and the corresponding contributions accounted for 17.89–32.73%, 28.84–46.22%, and 21.05–53.27%, respectively. Additionally, desorption characteristics of Pb illustrated that WBC_PMA owned more prominent stabilization ability than that of WBC and WBC_PMB. The findings of this study suggested that pre-modification method increased the contents of active groups in biochar and strengthened the removal efficiency of Pb ultimately. Due to the complexity of the actual Pb-containing wastewater environment, it was necessary to evaluate the effects of various factors on the stabilization performance of the pre-modified biochar in further.

Sericin Grafting onto Cashmere Fiber and Its Properties Investigation

ABSTRACT Cashmere fiber is pretreated with oxygen low temperature plasma to increase the content of polar groups (-OH, -COOH) on the surface. Then by using aziridine crosslinker and polycarbodiimide crosslinker, the sericin with health-care function is grafted onto the surface of the pretreated cashmere fiber. Plasma treatment is optimized after the assessing of methylene blue staining and fiber tensile strength. The grafting rate of sericin indicates that both aziridine and polycarbodiimide crosslinker could play a bridging role. Compared with untreated fiber, oxygen plasma treatment can improve the grafting rate significantly. The chemical changes and morphological structures of the fiber surface are analyzed by infrared spectroscopy and scanning electron microscope. After modification, cashmere exhibited good antibacterial and antioxidant properties. In addition, the fiber still has excellent dyeability while its crimp property and whiteness are slightly reduced.

Investigation of Antimicrobial Activity of DBD Air Plasma-Treated Banana Fabric Coated with Natural Leaf Extracts.

This paper focuses on the investigation of the antimicrobial activity of banana fabric treated with dielectric barrier discharge (DBD) plasma. The fabric was exposed to air plasma for varying treatment times of 1–5 min followed by coating with green tea (Camellia sinensis) and tulsi (Ocimum sanctum) leaf extracts at five different concentrations. The treated fabric was evaluated in terms of surface wettability by a range of tests like wet-out time analysis, hydrophilicity test, and contact angle measurements. The functional groups formed on the treated fabric were analyzed by attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy. The surface morphology was studied using atomic force microscopy (AFM) and scanning electron microscopy (SEM), and the surface chemistry was studied using X-ray photoelectron spectroscopy (XPS). The FTIR and XPS analysis results indicate that the plasma-treated fabric was found to have a higher concentration of polar groups (−COOH, −OH, −C=O) that has improved surface hydrophilicity and functionality. The antimicrobial activity of the treated fabric surface was determined both qualitatively and quantitatively by the agar plate method and modified Hoenstein test, against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. An improvement in the antimicrobial property was observed in plasma-treated banana fabric coated with natural extracts even after four washing cycles. This study suggests that air DBD plasma treatment followed by the absorption of tea/tulsi leaf extracts can serve as a better tool for developing natural antimicrobial textiles, which could serve the purpose in medical and healthcare sectors concerning recent times. It has eventually led to better absorption of plant extracts, thereby increasing their antimicrobial activity.

Role of polar and apolar moieties in water adsorption by humic acids under arid conditions

In arid soils, humic acids (HAs) are used as amendments to improve water uptake from the atmosphere. This method of harvesting water involves several steps depending on the relative humidity (RH). At low RH, water is adsorbed solely on primary sorption sites such as polar groups. As RH increases, more water is adsorbed on polar groups forming secondary sorption sites, which grow as the RH increases. As a result, the neighboring sorption sites can connect to form water molecule bridges (WaMBs). The WaMBs are responsible for the transport of water in the form of clusters into hydrophobic pores resulting in an increase in water content in organic matter (OM), swelling of OM and formation of phase water. HA being a complex mixture complicates the understanding of the relationship between the proportion of polar groups and properties of water. The understanding of these relationships can guide the design of humic-based amendments applicable in arid systems. To address this issue, seven HAs were characterized by nuclear magnetic resonance followed by the investigation of the properties of water (water content, strength of WaMBs and strength of water binding) on the HAs. Results showed that the content of polar groups positively correlated with the amount of water adsorbed by HA and the stability of WaMBs. It was found that presumably apolar moieties such as aromatics and phenols increased the binding energy of water to HA thereby appearing to be responsible for preventing the desiccation. In addition, between 44 and 76% RH, the WaMB stability positively correlated with O-alkyl and peptides moieties. Therefore, both polar and apolar domains influence water properties depending on RH. We conclude that this synergism is an advantage in systems composed of hydrophobic and hydrophilic molecules held together by weak interactions providing high flexibility to the system under arid conditions.

Influence of carbon dioxide plasma treatment on the dry adhesion of vertical aligned carbon nanotube arrays

Vertical aligned carbon nanotube (VACNT) arrays used as dry adhesive materials have broad prospects in the applied fields of space, medicine and electronics. The adhesion of VACNT arrays is believed to be related not only to the nano-array structure and a clean surface, but also to chemical composition. Here, radio-frequency (RF) carbon dioxide (CO2) plasma treatment is introduced as an effective method for purifying and functionalizing the surface to improve the dry adhesive performance of VACNT arrays. Scanning electron microscopy showed that the VACNT arrays retained the alignment architecture with minimal damage at low power. X-ray photoelectron spectroscopy and contact angle tests revealed that the content of non-polar components (C = C bonds) decreased after treatment, while the content of polar groups (C = O and O–C = O bonds) increased, which changed the surface polarity of the VACNT arrays. Raman analyses and transmission electron microscopy demonstrated that amorphous carbon can be selectively removed with increasing time (0–18 min), but was continuously generated with increasing power (30–90 W). The best adhesive strength of 18 N cm−2 (increased by 39%) was obtained after CO2 plasma treating for 10 min at 30 W power, which was attributed to the combined action of purification and polarization.

Surface charge dissipation and DC flashover characteristic of DBD plasma treated epoxy resin/AlN nanocomposites

This paper presents the mechanism of the surface charge dissipation and flashover voltage of epoxy resin (EP) with nano aluminum nitride (AlN) composites enhanced by dielectric barrier discharge (DBD) plasma treatment in open air. Surface conductivity, surface potential decay (SPD), flashover voltage, Fourier transform infrared (FT-IR) and surface roughness were measured to evaluate the electrical and physicochemical properties of EP/AlN nanocomposite samples before and after the plasma treatments. It is found that surface conductivity is evidently increased with the increase of the plasma treatment time. Moreover, the SPD of the plasma treated samples after positive and negative corona charging are enhanced. However, the positive charge dissipation is influenced more significantly by the treatment. Both the positive and negative flashover voltage are improved after the plasma treatment, and the amplitude of negative flashover voltage is higher than the positive flashover voltage in each case. Physicochemical measurements show that the content of polar groups is improved after the plasma treatment, and the surface roughness is continuously increased with the increment of the plasma treatment time. The calculated trap distribution demonstrates that the amount of both shallow holes trap and shallow electron trap are increased after the plasma treatment. This investigation attributes the enhanced SPD and improved flashover voltage to the increased surface conductivity, the more amount of shallow traps and the improvement of the sample surface roughness.

Surface modification of reduced graphene oxide‐polyaniline nanotubes nanocomposites for improved supercapacitor electrodes

AbstractIn the present work, irradiation with high energetic ions has been used for surface, structural, and morphological modifications of reduced graphene oxide (RGO) and polyaniline nanotubes (PAniNTs) nanocomposites with a view to enhance their electrochemical performance as supercapacitor electrode. High‐resolution transmission electron microscope micrographs depict defect induced fragmented morphology with stable inner hollow tubes up to a fluence of 2.2 × 1012 ions cm−2, above which drastic degradation of PAniNTs is observed. Irradiation induced annealing effects and structural disorder at varied irradiation fluences have been investigated by micro‐Raman spectroscopy. Formation of shorter PAniNTs of higher surface area due to generation of ion irradiation induced defects and their reorganization results in increased Brunauer‐Emmett‐Teller specific surface area and porosity. Surface energy and wettability of the electrodes increase upon ion irradiation, which improves electrode‐electrolyte interaction at the interface. Surface free energy calculations indicate increased concentration of polar groups on the nanocomposite electrode surface upon irradiation. Electrochemical performance studies indicate enhancement in specific capacitance and cyclic stability from 448 F g−1 and 89% for unirradiated nanocomposite to 482 F g−1 and 92%,, respectively, for the nanocomposite irradiated at 2.2 × 1012 ions cm−2 fluence, which is attributed to the increased surface energy and porosity upon irradiation giving rise to increased electrochemically active sites for charge storage in the electrode.

Mechanisms of surface charge dissipation of silicone rubber enhanced by dielectric barrier discharge plasma treatments

This paper investigates mechanisms of the surface charge dissipation of silicone rubber (SiR) after dielectric barrier discharge (DBD) plasma treatments in an open air. Electrical and physicochemical properties of the untreated and plasma treated samples were evaluated by surface and volume conductivity, surface potential decay (SPD) measurements, Fourier transform infrared (FT-IR), and water contact angle tests. Results show that the surface conductivity of the plasma treated samples evidently increases with the treatment time. The samples with a longer DBD plasma treatment time enhance the SPD rate after the positive and negative corona charging. However, an abnormal surface potential variation is observed at the beginning of the SPD after the negative corona charging. It is found that the top-bottom surface plasma treatment can further accelerate the SPD of the samples compared with the untreated and single surface plasma treated samples. The physicochemical analysis shows that the concentration of polar groups is increased after the plasma treatment, and the water contact angle is consistently declined with the increase of the plasma treatment time. The calculated trap distribution illustrates that the hole trap energy and the electron trap density of the sample are decreased after the plasma treatments. This investigation attributes the measured SPD of the untreated sample and single surface treated samples to the electrical conduction along the sample surface, but the SPD of the top-bottom surfaces plasma treated samples is enhanced by the charge neutralization and transportation through the material bulk as well as the sample top surface conduction.