Increasing Polymerization Time Research Articles

Polypyrrole and cotton fabric‐based flexible micro‐supercapacitors

AbstractWith the development of wearable electronic devices, there has been extensive research interest in portable energy supply systems. In this study, traditional cotton fabrics are finished with a water repellent coating and a single‐sided polyurethane (PU) coating to impart hydrophobicity. The hydrophobic lightweight cotton fabric can float on the surface of the pyrrole polymerization system solution. With increasing polymerization time, the pyrrole continues to polymerize and deposit on the side in contact with the fabric, resulting in a one‐sided conductive fabric. The highest doping level was obtained for the polypyrrole (PPy) coating for polymerization time of 12 h. For PPy coating thickness of 18 μm, the square resistance was as low as 220 Ω/sq. The PPy‐12 fabric electrode showed excellent electrochemical performance and cycling stability. An interdigitated pattern was etched on the surface of the one‐sided conductive fabric (PPy‐12) using a N, N‐dimethylformamide solution. Fabric micro‐supercapacitors were obtained by assembling with a H2SO4/PVA gel electrolyte. The fabric micro‐supercapacitor exhibited good flexibility and electrochemical energy storage properties. For current density of 0.08 mA/cm2 and power density of 19.1 μW/cm2, the energy density of the device was 0.09 μWh/cm2. After 3000 cycles, the micro‐supercapacitor retained approximately 85% of the capacitance. Thus, fabric‐based flexible micro‐supercapacitors have excellent application potential in the field of energy storage.

Durable poly(N-isopropylacrylamide) grafted PDMS micropillared surfaces for temperature-modulated wetting

Surface grafting of polymer brushes has become an area of significant research to deliver desired material properties such as smart wetting. In this research the grafting of Poly(N-isopropylacrylamide)(PNIPAAm) by benzophenone-initiated UV polymerization on micro-pillared surfaces was performed. By increasing polymerization time PNIPAAm first coats the top of the mushroom pillars then bridges the gap between pillars rather than penetrating the inter-pillar spaces due to the intrinsic features of Poly(dimethylsiloxane) (PDMS) pillars. This enables controlled grafting via control of polymerization time. Above the lower critical solution temperature (LCST), the grafted PNIPAAm brushes are immiscible with water and the surfaces displayed a strongly hydrophobic state with a large contact angle of 120°. Below the LCST, the grafted PDMS micropillars surface swells and absorbs water significantly faster than flat grafted surfaces, displaying a hydrophilic state with a small contact angle 33°. Interestingly, grafting on micropillars as opposed to flat surfaces enhanced the magnitude of the contact angle change across PNIPAAm’s hydrophobicity-hydrophilicity switch and enhances the speed of graft hydration. The grafted surface was further found to be durable under strong water jetting. Thus, a significant synergetic effect of the grafted PNIPAAm and micropillars delivered a durable temperature-modulated smart wetting property with a transition from the hydrophobic to hydrophilic state.

Effects of different “rigid-flexible” structures of carbon fibers surface on the interfacial microstructure and mechanical properties of carbon fiber/epoxy resin composites

In order to comprehend the influence of different “rigid-flexible” structures on the interface strength of carbon fiber(CF)/epoxy composites, CNTs was firstly chemically grafted on CFs surface, and then polyamide (PA) was grafted onto CF-CNTs surface through varying anionic polymerization time of caprolactam [CF-CNTs-PAn (n = 6 h, 12 h, 24 h)]. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy indicated the successful establishment of CNTs and PA. TGA demonstrated the different grafting amounts of CF-CNTs-PAn (n = 6 h, 12 h and 24 h). SEM images revealed a compactness and uniform coverage of the CNTs/PA, with increasing polymerization time, the CF and CNTs surface was covered by a thick layer of PA. The surface energy increased and then decreased. The optimal interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) of the CF/epoxy composites with a polymerization time of 12 h (CF-CNTs-PA12h) was 86.7 and 85.4 MPa, which was 77.6% and 45.7% higher than that of untreated CF/epoxy composite. As the polymerization time grew, the impact toughness and tensile strength of CF/epoxy composites enhanced and conductivity of CF/epoxy composite reduced. In addition, the mechanisms of reinforcement and toughening were also illuminated. This work would provide a certain theoretical basis for the preparation and applications of high-performance CF composites with different structures.

A Lysine-Modified Polyethersulfone (PES) Membrane for the Recovery of Lanthanides.

Rare-earth elements (which include all lanthanides, scandium, and yttrium) play a key role in many fields including oil refining, metallurgy, electronics manufacturing, and other high-technology applications. Although the available lanthanide resources are enough for current levels of manufacturing, increased future demand for lanthanides will require new, efficient recovery methods to provide a sustainable supply. Membrane adsorbers are promising separation materials to recover lanthanides from high volumes of wastewater due to their tailorable surface chemistry, high binding capacity and high throughput. In this work, membrane adsorbers were synthesized by first using ultraviolet-initiated free radical polymerization to graft a poly(glycidyl methacrylate) (p-GMA) layer to the surface of polyethersulfone membranes. Then, the reactive epoxy groups of the grafted p-GMA were used for the covalent attachment of lysine molecules via a zinc perchlorate-catalyzed, epoxide ring-opening reaction at 35°C. Changes in membrane surface chemistry throughout the functionalization process were monitored with Fourier Transform Infrared Spectroscopy. The degree of grafting for the p-GMA film was quantified gravimetrically and increased with increasing polymerization time. Equilibrium adsorption experiments were performed for single specie solutions of La3+, Ce3+, Nd3+, Na+, Ca2+, and Mg2+ at pH 5.25 ± 0.25. Lysine-modified membranes showed negligible uptake of Na+, Ca2+, and Mg2+. The maximum capacities modeled by the Langmuir isotherm for La3+ and Ce3+ were 6.11 ± 0.58 and 6.45 ± 1.29 mg/g adsorbent, respectively. Nd3+ adsorbed to the membrane; however, the fit of the Langmuir model was not significant and it adsorbed to a lower extent than La3+ and Ce3+. Lower adsorption of the higher charge density species indicates that the primary binding mode is through the amine moieties of lysine and not the carboxylic acid. Dynamic adsorption experiments were conducted with 1 ppm La3+ feed solutions at different flow rates using either a single membrane or three membranes in series. The dynamic binding capacity at 50% breakthrough was independent of flowrate within the tested range. The low-temperature membrane functionalization methodology presented in this work can be used to immobilize biomolecules with even higher specificity, like engineered peptides or proteins, on membrane surfaces.

Non-isothermal decomposition kinetics of in-chain functionalized poly(MMA-co-ethylene)

Efficient incorporation of polar monomers in polyolefin can lead to many desirable properties in the parent chain. Herein, we report the synthesis of ethylene and methyl methacrylate (MMA)-based copolymers by transition metal-catalysed reverse atom transfer radical polymerization technique with controlled ethylene feed pressure. Successful copolymerization was confirmed by 1H nuclear magnetic resonance analysis. With increasing polymerization time, resultant copolymers exhibit bimodal molecular weight distributions with controlled high molecular weight component and less-controlled low molecular weight component as confirmed by size-exclusion chromatography analysis. Morphological and crystal structures of the copolymer were established using scanning electron microscope and X-ray diffraction analysis, respectively. Thermogravimetric analysis of the copolymer under non-isothermal condition shows a two-step decomposition process with the major decomposition in the range of 320–450 °C. Based on approaches of Friedman and Flynn–Wall–Ozawa, model-free multivariate nonlinear regression analyses were performed to find out the formal mechanisms, kinetic model and its corresponding kinetic triplets. The results revealed the nth-order (Fn) mechanism responsible for the decomposition of the copolymer. The estimated kinetic parameters for the decomposition of poly(MMA-co-ethylene) copolymer were Ea= 227.80 kJ mol−1 and A = 6.76 × 1015 s−1.

Biowaste-derived carbon black applied to polyaniline-based high-performance supercapacitor microelectrodes: Sustainable materials for renewable energy applications

Biowaste, derived from cooking-oven-produced carbon nanoparticles (WCP), are incorporated into polyaniline (PANI) via in-situ chemical oxidative polymerization to achieve excellent electrochemical properties for application in supercapacitors. The WCP-PANI composite electrodes have shown high-performance charge storage, due to combinatorial effect of electrical double layer capacitance from WCP and pseudocapacitance from PANI. With increase in the WCP percolation, work function of PANI is increased, which improves the charge-trapping capabilities of composites. For such distinct charge-trapping mechanism, areal capacitance of the composite microelectrode remains near-constant with increase in scan rate or current density. This indicates the suppression of diffusion limitations at higher scan rates to considerably enhance the rate capability. Also, with increasing polymerization time, strong interaction in this conjugated system greatly improves the charge-transfer reaction between PANI and WCP. The areal capacitance of the composite electrode is found to increase more than 600 times over pure PANI electrode. Moreover, energy-power performance of the microelectrode reveals almost 550% increment in the power density with a mere 1% decrement in energy density. Such rationally synthesized WCP-PANI composite electrodes using biowaste carbon nanomaterials, provide opportunities for the development of next-generation green-supercapacitors with improved energy storage performance.

Effect of alkylaluminium on the regio- and stereoselectivity in copolymerization of isoprene and butadiene using TiCl4/MgCl2 type Ziegler-Natta catalyst

Alkylaluminums as one of the most important components of the heterogeneous MgCl2-supported (TiCl4/MgCl2) type Ziegler-Natta catalysts, play significant roles in yielding active species with varied regio- and stereoselectivity. Studying the contribution of alkylaluminums on the conjugated diene isoprene (Ip) and butadiene (Bd) copolymerizations with TiCl4/MgCl2 - alkylaluminum catalysts system is little reported. In this work, effects of various alkylaluminums including triethylaluminium (TEA), triisobutylaluminium (TiBA), diisobutylaluminium hydride (DiBAH) and diethylaluminum chloride (DEAC) on the copolymerization behaviors of Ip and Bd using the TiCl4/MgCl2 - alkylaluminum catalysts system, such as catalytic activity, active center numbers, butadiene incorporation, trans-1,4 stereoselectivity, molecular weight Mw as well as molecular weight distribution Mw/Mn of copolymers were first investigated. TEA with smaller size ethyl groups showed higher copolymerization activity, higher reducing ability and then yielding more active center numbers ([C*]/[Ti]) when compared with TiBA, DiBAH and DEAC. Microstructure of copolymers gradually transformed from the cis-1,4/trans-1,4 mixed structure in the initial polymerization period to the finally high trans-1,4 structure, indicating a transformation of the active center nature during the early polymerization stage, which can be accelerated effectively through the addition of DEAC into the TiCl4/MgCl2-TEA catalyst system. TEA with smaller size ethyl group showed higher transformation rate from the mixed structures of trans-1,4 and cis-1,4 to highly trans-1,4 structure. The active center numbers of the copolymerization systems increased gradually with increasing time until reaching a stable level. The Mw/Mn of copolymers showed interesting evolution with increasing polymerization time from broad distribution with low to medium molecular weight fractions in the initial polymerization stage to relatively narrow distribution with high molecular weight fractions. The contribution of alkylaluminium compounds on the structure of active species which determining the regio- and stereoselectivity of Ip and Bd copolymerization using heterogeneous TiCl4/MgCl2 type catalysts were discussed in details

Trans-1,4- stereospecific copolymerization of isoprene and butadiene catalyzed by TiCl4/MgCl2 type Ziegler-Natta catalyst II. Copolymerization Kinetics and Mechanism

Stereospecific copolymerization mechanism of isoprene (Ip) and butadiene (Bd) with heterogeneous TiCl4/MgCl2-Al(i-Bu)3 Ziegler-Natta catalyst was investigated for the first time in this paper. Copolymerization kinetics of isoprene and butadiene revealed that copolymers with high cis-1,4 units were observed in the initial stage, then the trans-1,4/cis-1,4 ratio increased gradually to the finally dominant trans-1,4-sequecnc with increasing polymerization time. The Al/Ti ratio influenced the catalytic efficiency, trans-1,4-sequecnc percentage and the butadiene incorporation (FBd). The copolymers obtained at different conversion and Al/Ti ratio were isolated to a series of fractions by stepwise isothermal crystallization fractionation from 80 °C to −20 °C. The trans-1,4-unit percentage, trans-trans and trans-cis placement, butadiene-isoprene (BI or IB) dyad sequence concentration, FBd, molecular weight and molecular weight distribution of the main fractions were analyzed by 1H NMR,13C NMR, TGA, GPC, DSC and WAXD characterization, which provided powerful evidences for the presence and evolution of active centers with different catalytic stereospecificity. Therefore, the possible active centers and trans-1,4 stereospecific copolymerization mechanism of isoprene and butadiene using heterogeneous Ziegler-Natta catalyst system was proposed accordingly.

Polymerization of Butyl Methacrylate Catalyzed by Salicylaldehyde-Imine Zirconium /Al(i-Bu)3 System

A new kind of zirconium(Zr) complex containing ligand of salicylaldehyde-imine was successfully synthesized with ZrCl4·2THF and salicylaldehyde-imine as raw materials. The ligand was characterized by means of 1HNMR, IR, and GC-MS, and Zr complex was characterized by means of 1HNMR and IR, respectively. The Zr complex, combined with co-catalyst of Al(i-Bu)3, was explored to be effective catalytic system for the polymerization of butyl methacrylate(BMA), to prepare poly-n-butyl methacrylate (PBMA), which was characterized by IR, 13C-NMR and GPC. Compared with other double-component (MAO/Cat, AlEt3/Cat) catalytic systems, catalytic system of Al(i-Bu)3 and the Zr complex provided the best catalytic activity under the same conditions. The influence of polymerization parameters, such as molar ratio of Al(i-Bu)3/Cat and BMA/Cat, polymerization temperature and polymerization time, was studied with Zr complex/Al(i-Bu)3 system. With increasing polymerization time from 4 to 24 hour, the monomer conversion increased from 40.14% to 96.56%. Viscosity-average molecular weight (Mv) of PBMA, detected by the viscosity methodology, increased from 12.67×104 Da to 44.97×104 Da and lower molecular weight distribution was obtained. According to these results, the Zr complex contained ligand of salicylaldehyde-imine was a kind of readily, long lifetime and high activity catalyst for BMA polymerization.

Surface Modification of Wood Flour via ARGET ATRP and Its Application as Filler in Thermoplastics.

Wood flour is particularly suitable as a filler in thermoplastics because it is environmentally friendly, readily available, and offers a high strength-to-density ratio. To overcome the insufficient interfacial adhesion between hydrophilic wood and a hydrophobic matrix, a thermoplastic polymer was grafted from wood flour via surface-initiated activators regenerated by electron transfer-atom transfer radical polymerization (SI-ARGET ATRP). Wood particles were modified with an ATRP initiator and subsequently grafted with methyl acrylate for different polymerization times in the absence of a sacrificial initiator. The successful grafting of poly(methyl acrylate) (PMA) was demonstrated using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and water contact angle (WCA) measurements. To confirm the control over the polymerization, a cleavable ATRP initiator was immobilized on the particles, allowing the detachment of the grafted polymer under mild conditions. The grafted particles were incorporated into a PMA matrix using solvent casting and their influence on the mechanical properties (Young’s modulus, yield strength, and toughness) of the composite was investigated. Tensile testing showed that the mechanical properties improved with increasing polymerization time and increasing ratio of incorporated grafted particles.

Metal-Free Photocatalysts C3N3S3 and its Polymers: Solubility in Water and Application in Benzylic Alcohols Oxidation Under Visible Light

Metal-free photocatalysts trithiocyanuric acid (C3N3S[Formula: see text] and its polymers were one-step synthesized and used for selective aerobic oxidation of benzyl alcohol under visible light. The S–S bridged C3N3S3 polymers showed higher oxidation activity with increasing polymerization time and reached a maximum at 40[Formula: see text]h. As a major factor, catalysts’ solubility in water at different temperatures (from 298.15[Formula: see text]K to 368.15[Formula: see text]K) was measured at atmospheric pressure. The obtained data were correlated by polynomial empirical equation and modified Apelblat equation, respectively. Experimental results proved that the solubility of C3N3S3 and its polymers increased with increasing temperature. The solubility of C3N3S3 polymers with lower polymerization degree (DP) were better than that of parent C3N3S3 owing to the hydrophilicity caused by a low symmetry and disorder structure, whereas the higher DP could lead to the decrease of polymer solubility and further affect the photocatalytic activity. Thermodynamic properties of the solution system including the enthalpy ([Formula: see text] and heat capacity ([Formula: see text]) were calculated by the modified Apelblat equation.

Comparative Investigations on Optimum Polymerization Conditions for the Synthesis of a Sustainable Poly(Lactic Acid)

The development of synthetic biodegradable polymers using solvent free polymerization has a unique potential to be used as sustainable polymers in biomedical applications. The aim of this work was to synthesize and characterize a sustainable class of poly(lactic acid) (PLA) under different operating conditions via direct polycondensation of lactic acid (LA). Several parameters were tested including the absence of solvents and catalysts on the polymerization, in addition to polymerization temperature and time. Polymerization conditions were evaluated using response surface method (RSM) to optimize the impact of temperature, time, and catalyst. Results showed that molecular weight (Mw) of PLA increased with increasing polymerization time. Highest Mw of 28.4 kD with relatively a broad polydispersity 1.9 was achieved at polymerization temperature 170 °C at 24 h in the free solvent polymerization. This led to a relevant inherent viscosity of 0.37 dl/g. FTIR spectra exhibited a disappearance of the characteristic peak of the hydroxyl group in LA at 3482 cm−1 by increasing the intensity of carbonyl group. The 1H nuclear magnetic resonance (NMR) exhibited the main chain at 5.22 ppm and the signal of methyl proton at 1.61 ppm as well as a signal at 4.33 and 1.5 assigned to the methane proton next to the terminal hydroxyl group and carboxyl group respectively. Meanwhile, the PLA synthesized with a catalyst [Sn(Oct)2] in a free solvent demonstrated comparatively high thermal transition properties of glass transition, melting, and crystallinity temperatures of 48, 106, and 158 °C, respectively. These results are of significant interest to further expand the use of PLA in biomedical applications.

Fabrication of hollow polymer particles using emulsions of hydrocarbon oil/fluorocarbon oil/aqueous surfactant solution

We have examined the influence of sodium dodecylsulfate (SDS) on the formation of emulsions consisting of hydrocarbon oil/fluorocarbon oil/water and the fabrication of hollow polymer particles by simple radical polymerization using these emulsions. Emulsions consisting of ternary mixtures of styrene/perfluoro-n-octane (PFO)/aqueous SDS solution are prepared at 80°C. Light and fluorescence microscopy observations indicate that the ternary mixtures are O/W (oil-in-water)-type emulsions. It is found that PFO droplets are present on the surface of styrene droplets. In other words, the oil droplets show Janus-type morphologies consisting of styrene and PFO. When the ternary mixtures of styrene/PFO/aqueous SDS solution are polymerized at 80°C, subsequent SEM observations indicate that the hollow cup-type polystyrene particles with a single hole on the surface are fabricated by polymerization using the Janus emulsion droplets. The hole size decreases with increasing polymerization time. These results suggest that morphologies of emulsions of ternary mixtures of hydrocarbon oil, fluorocarbon oil, and aqueous SDS solution contribute to those of polymer particles fabricated by the radical polymerization. Submicron capsules containing aqueous solutions of a fluorescent material are prepared through the hollow cup-type particles.

Pore size-controlled carbon aerogels for EDLC electrodes in organic electrolytes

Pore size-controlled carbon aerogels (CA_X) are prepared from two starting materials: resorcinol and formaldehyde. Carbon aerogels with different pore sizes are successfully obtained by simply varying the polymerization time (X) in the polycondensation of resorcinol and formaldehyde. Pore sizes of the carbon aerogels monotonically increase with increasing polymerization time. The pore size of the carbon aerogel plays an important role in determining its electrochemical behavior (i.e., specific capacitance in EDLC) especially at high current density. A sufficiently large pore size in a carbon aerogel is required for easy transport of electrolyte ions, and these types of carbon aerogels provide excellent electrochemical performance as an EDLC electrode. CA_20, which was polymerized for the longest time, have the largest pore size and the largest pore volume. CA_20 exhibit the highest specific capacitance due to facile electrolyte ion transport. As a result, design of carbon aerogels with a sufficiently large pore size while maintaining a high specific surface area is very important for developing carbon aerogels for use in EDLC electrodes. In addition, we propose a schematic reaction pathway for the preparation of carbon aerogels in ambient conditions from resorcinol and formaldehyde using a base catalyst based on the characterization results.

Superhydrophobic Surfaces with Very Low Hysteresis Prepared by Aggregation of Silica Nanoparticles During <I>In Situ</I> Urea-Formaldehyde Polymerization

We present a new method for the preparation of superhydrophobic materials by in situ aggregation of silica nanoparticles on a surface during a urea-formaldehyde (UF) polymerization. This is a one-step process in which a two-tier topography is obtained. The polymerization is carried out for 30, 60, 120, 180, and 240 min on silicon shards. Silicon surfaces are sintered to remove the polymer. SEM and AFM show both an increase in the area covered by the nanoparticles and their aggregation with increasing polymerization time. Chemical vapor deposition of a fluorinated silane in the presence of a basic catalyst gives these surfaces hydrophobicity. Deposition of this low surface energy silane is confirmed by the F 1s signal in XPS. The surfaces show advancing water contact angles in excess of 160 degrees with very low hysteresis (< 7) after 120 min and 60 min polymerization times for 7 nm and 14 nm silica, respectively. Depositions are successfully demonstrated on glass substrates after they are primed with a UF polymer layer. Superhydrophobic surfaces can also be prepared on unsintered substrates.

Removal of Acid Orange 7 Dye from Water Via Plasma-Polymerized Allylamine-Coated Quartz Particles

A novel method of acid orange 7 (AO7) removal has been developed via the deposition of plasma-polymerized allylamine (ppAA) films on quartz particles. ppAA films were deposited at a power of 25 W, allylamine flow rate of 4.4 sccm and polymerization time of 5 to 60 min. Polymerization time had a significant effect on surface chemistry where the XPS nitrogen concentration, XPS C-O, C-N concentration, isoelectric point and the number of positively charged groups per nm2 all increased with increasing polymerization time. Increasing polymerization time increased AO7 adsorption due to greater concentrations of positively charged amine groups on the surface. The pH and initial AO7 concentration were varied to investigate their effect on AO7 adsorption. Increasing the initial AO7 concentration increased adsorption for all polymerization times. pH had a significant effect on AO7 adsorption with maximum adsorption at pH 3 and significantly less at pH values of 5–9. Regeneration of ppAA-coated quartz particles for up to 4 cycles using pH 12 Milli-Q water resulted in only slight losses in adsorption capacities. ppAA-coated particles have shown to successfully remove AO7 dye from solution and therefore demonstrate potential for use in the treatment of industrial dye wastestreams.

Physicochemical characteristics of poly(piperazine-amide) TFC nanofiltration membrane prepared at various reaction times and its relation to the performance

Abstract Poly(piperazine-amide) thin film composite (TFC) nanofiltration (NF) membranes were prepared via interfacial polymerization (IP) of trimesoyl chloride (TMC) in cyclohexane and piperazine (PIP) in water. The effect of polymerization time on the physicochemical characteristics of poly(piperazine-amide) layers and the final membrane performance was studied in detail. The morphological structures of prepared membranes were investigated using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), by contrast, was used to determine the chemical characteristics of the membranes. It is evident that the surface roughness increased with increasing polymerization time due to the formation of a supergranule-like structure over the interfacially synthesized poly(piperazine-amide) layer. Moreover, increasing the polymerization time led to a dramatic reduction of water permeability due to the significant increase of crosslinking poly(piperazine-amide) barrier layers. Experimentally determined data showed that the TFC NF membrane prepared at 10 s of polymerization time experienced 51.2 l/m2.h of water permeability with 97.02% of Na2 SO4 salt rejection at an operating pressure of 0.6 MPa.

Anti-biofouling of polyamide reverse osmosis membranes using phosphorylcholine polymer grafted by surface-initiated atom transfer radical polymerization

The zwitterionic phosphorylcholine polymer was covalently grafted on a polyamide reverse osmosis (RO) membrane for anti-biofouling, using surface-initiated atom transfer radical polymerization (ATRP). Polyamide RO membranes modified with hydroxyl groups of diethanolamine (DEA) were fabricated by interfacial polymerization. The ATRP initiator, 2-bromoisobutyryl bromide (BIBB), was immobilized on the fabricated membrane, by condensation between DEA hydroxyl groups and BIBB carboxylic bromide. BIBB immobilization was confirmed by X-ray photoelectron spectroscopy. ATRP was carried out using 2-methacryloyloxyethyl phosphorylcholine (MPC) and immobilized BIBB. Attenuated total reflectance Fourier transform infrared spectra indicated that the MPC polymer was grafted on the membrane surface. The amount of grafted MPC polymer increased with increasing polymerization time. The surface morphology of the MPC polymer-grafted membranes became smoother with increasing polymerization time. The polyamide RO membrane with grafted MPC polymer retained its initial water flux in a crossflow bacterial filtration test, preventing bacterial adhesion on the surface.

Synthesis of polypyrrole nanoparticles by batch and semicontinuous heterophase polymerizations

Nanoparticles of semiconducting polypyrrole (PPy) were synthesized by batch heterophase (BHP) and semicontinuous heterophase polymerization (SHP) using ferric chloride (FeCl3), potassium persulfate (KPS), or ammonium persulfate (APS) as the oxidizing agent, sodium dodecyl sulfate (SDS) as surfactant, and ethanol (EtOH) or iso-pentyl alcohol (iC5OH) as co-surfactants. In all cases, the molar ratios of monomer/oxidizing agent were 1/1. Pyrrol polymerization by BHP and SHP allowed using much lower percentages of surfactant than those employed in microemulsion polymerization of this monomer. The effects of temperature, oxidizing agent, and co-surfactant on conductivity were studied. The polymers were analyzed by transmission electron microscopy (TEM), UV/Visible and Fourier transform infrared (FTIR) spectroscopies, and cyclic voltammetry. Higher PPy conductivities were obtained by polymerizing at 0 °C with FeCl3 as the oxidizing agent, in the presence of iC5OH as co-surfactant. When the reaction was carried out by SHP with low reaction times, smaller particles with similar conductivities were obtained compared to those obtained by BHP; the conductivity of PPy decreases with increasing polymerization time, which can be explained by PPy overoxidation.

Composites of polyaniline and lead dioxide: preparation, characterization, and catalytic activity

This paper is devoted to the preparation of polyaniline/lead dioxide composites (PANI/PbO2) via chemical oxidation of aniline in H2SO4 medium using β-PbO2 as an oxidant. The parameters affecting the polymerization reaction are considered. These parameters are [aniline], amount of β-PbO2, stirring time, and different acids. The prepared composites were characterized by SEM, FT-IR, XRD, TGA, DTA, and elemental analysis. From XRD and FT-IR spectra, it was concluded that high molecular weight polymer could be obtained with high aniline concentration, high amount of β-PbO2, increasing polymerization time and polymerization of ANI at lower temperatures. Thermogravimetric study exhibited that the composite prepared using high amount of β-PbO2 has a higher thermal stability. The application of the composites in the oxidative degradation of Alizarin yellow G and Acid alizarin violet N dyes exhibited good catalytic activity in presence of H2O2 as an oxidant. The reactions followed first-order kinetics and the rate constants were determined.