Frontal polymerization synthesis and characterization of Konjac glucomannan‐graft‐acrylic acid polymers

Konjac glucomannan‐graft‐acrylic acid polymers, used as superabsorbent polymers (SAPs), were synthesized by frontal polymerization (FP). The features of front propagation including front velocity and maximum temperature (T_max) were influenced by the amount of glucomannan, initiator, and environment temperature. The graft copolymer was characterized by FTIR, DSC, and SEM. The amount of crosslinking agent mainly determined the crosslinking degree of SAPs that would affect the water absorbency and microstructure. Water absorbency of SAP was also investigated and most of them displayed high water absorption rate. The aforementioned results allow us to conclude that FP can be considered as a promising method to fabricate SAP for its excellent advantages. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3391–3398, 2009     

Synthesis,characterization and water absorbency properties of poly(acrylic acid)/sodium humate superabsorbent composite

A novel poly(acrylic acid)/sodium humate superabsorbent composite was synthesized by aqueous solution polymerization of acrylic acid using N, N′‐methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator in the presence of sodium humate. The effects on water absorbency such as initial monomer concentration, degree of neutralization of acrylic acid, amount of crosslinker, initiator and sodium humate, etc. were investigated. The water absorbency of the superabsorbent composite synthesized under optimal synthesis conditions with a sodium humate content of 20% exhibited an absorption of 1268 g H₂O/g sample and 93 g H₂O/g sample in distilled water and in 0.9 wt% NaCl solution, respectively. Swelling rate and water retention tests were also carried out. The results show that sodium humate, as a kind of functional filler, can enhance comprehensive properties of superabsorbent composite and reduce the product cost significantly. Copyright © 2005 John Wiley & Sons, Ltd.     

Radiation-induced graft polymerization of acrylic acid onto fluorinated polymers. I. Kinetic study on the grafting onto poly(tetrafluoroethylene-ethylene) copolymer

Direct radiation-induced grafting of aqueous acrylic acid (AAc) onto poly(tetrafluoroethylene-ethylene) (ET) film has been studied. The effect of grafting conditions such as monomer concentration, exposure dose, dose rate, and film thickness on the grafting yield was investigated. The dependence of the grafting rate on monomer concentration was found to be 1.2 order. The dependence of the grafting rate on dose rate was found to be 0.6 order regardless of the film thickness. The relationship between the grafting rate and film thickness gave a negative first-order dependence. The results suggest that the grafting process is mainly controlled by monomer diffusion, and it was concluded that this grafting system proceeded by the front mechanism. The swelling behavior increases linearly with degree of grafting. The electrical conductivity and mechanical properties for the trunk and grafted polymer were investigated at different irradiation doses in air and under vacuum irradiations. © 1992 John Wiley & Sons, Inc.     

Continuous precipitation polymerization of acrylic acid in supercritical carbon dioxide: The polymerization rate and the polymer molecular weight

The precipitation polymerization of acrylic acid in supercritical carbon dioxide was studied in a continuous stirred tank reactor with 2,2′‐azobis(2,4‐dimethylvaleronitrile) as the free‐radical initiator. The reactor temperature was between 50 and 90 °C, the pressure was 207 bar, and the average residence time was between 12 and 40 min. The product polymer was a white, dry, fine powder that dissolved in water. A wide range of polymer molecular weights (5–200 kg/mol) was obtained. The effects of the operating variables on the polymerization rate and on the polymer molecular weight were evaluated. The observed kinetics suggested that polymerization took place in both the supercritical fluid and the precipitated polymer particles. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2546–2555, 2005     

Polyaniline doped by a new class of dopants,benzoic acid and substituted benzoic acid: synthesis and characterization

This work reports on a new class of dopants, benzoic acid and substituted benzoic acids such as 2‐hydroxybenzoic acid, 2‐chlorobenzoic acid, 4‐nitrobenzoic acid, 2‐methoxybenzoic acid, 3‐methylbenzoic acid, 4‐methylbenzoic acid, 3‐aminobenzoic acid and 4‐aminobenzoic acid, for polyaniline. Benzoic acids can be used to dope polyaniline by mixing benzoic acid (or a substituted benzoic acid) with polyaniline in the common solvent 1‐methyl‐2‐pyrrolidone. Properties of benzoic acid doped polyaniline salts are studied using Fourier transform infra‐red, X‐ray diffraction spectroscopy, scanning electron microscopy, thermogravimetric analysis and conductivity measurements. The conductivity of polyaniline‐benzoic acid salt was found to be high (10⁻² S/cm) when compared to polyaniline‐substituted benzoic acid salts (10⁻³–10⁻⁵ S/cm). Copyright © 2005 John Wiley & Sons, Ltd.     

The synthesis and characterization of monodisperse poly(acrylic acid) and poly(methacrylic acid)

A number of polyacrylic (PAA) and polymethacrylic (PMAA) acids have been synthesized by living anionic polymerization of the monomeric tert-butyl esters followed by subsequent hydrolysis of the corresponding polyesters. The necessary precautions were taken in order to assure good molecular weight control, as well as high yields in the polymerization reactions. The intermediate and final polymers were characterized by gel permeation chromatography and NMR-H¹ spectrometry.     

Interpenetrating polymer network (IPN) nanogels based on gelatin and poly(acrylic acid) by inverse miniemulsion technique: synthesis and characterization

Novel interpenetrating polymer network (IPN) nanogels composed of poly(acrylic acid) and gelatin were synthesised by one pot inverse miniemulsion (IME) technique. This is based on the concept of nanoreactor and cross-checked from template polymerization technique. Acrylic acid (AA) monomer stabilized around the gelatin macromolecules in each droplet was polymerized using ammonium persulfate (APS) and tetramethyl ethylene diamine (TEMED) in 1:5 molar ratio and cross-linked with N,N-methylene bisacrylamide (BIS) to form semi-IPN (sIPN) nanogels, which were sequentially cross-linked using glutaraldehyde (Glu) to form IPNs. Span 20, an FDA approved surfactant was employed for the formation of homopolymer, sIPN and IPN nanogels. Formation of stable gelatin-AA droplets were observed at 2% surfactant concentration. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) studies of purified nanogels showed small, spherical IPN nanogels with an average diameter of 255 nm. In contrast, sIPN prepared using the same method gave nanogels of larger size. Fourier-transform infrared (FT-IR) spectroscopy, SEM, DLS, X-ray photoelectron spectroscopy (XPS) and zeta potential studies confirm the interpenetration of the two networks. Leaching of free PAA chains in sIPN upon dialysis against distilled water leads to porous nanogels. The non-uniform surface of IPN nanogels seen in transmission electron microscopy (TEM) images suggests the phase separation of two polymer networks. An increase of N/C ratio from 0.07 to 0.17 (from PAA gel to IPN) and O/C ratio from 0.22 to 0.37 (from gelatin gel to IPN) of the nanogels by XPS measurements showed that both polymer components at the nanogel surface are interpenetrated. These nanogels have tailoring properties in order to use them as high potential drug delivery vehicles for cancer targeting.     

Novel synthesis of N‐substituted polyacrylamides: Derivatization of poly(acrylic acid) with amines using a triazine‐based condensing reagent

Poly(acrylic acid) (PAA) was derivatized through the reaction of its pendant carboxylic acid (CO₂H) groups with a wide range of amine‐terminated molecules. These molecules contained alkyl, hydroxyl, sulfonic acid, or perfluoroalkyl groups. N‐substitution of PAA was carried out by the simple addition of 4‐(4,6‐dimethoxy‐1,3,5‐triazin‐2‐yl)‐4‐methylmorpholinium chloride (DMTMM), a triazine‐based condensing reagent, to a mixture of PAA and amine‐terminated molecules. From proton nuclear magnetic resonance and infrared spectroscopy, it was confirmed that these functional molecules were introduced into the PAA side chain via amide bonds. By the alteration of the synthetic conditions, functional side‐chain contents of greater than 95% were achieved for aqueous reactions with taurine, ethanol amine, and butyl amine. Side‐chain conversion was limited to ≤80% for reactions with perfluoroalkyl amines in methanol. Thus, DMTMM is an attractive replacement for carbodiimide condensing reagents such as 1,3‐dicyclohexylcarbodiimide and 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 126–136, 2006     

Synthesis and characterization of phosphorized polyaniline doped with phytic acid and its anticorrosion properties for Mg-Li alloy

A phosphorized polyaniline (PANI) doped with phytic acid (PhA) was synthesized by the chemical oxide method with PhA as a dopant and applied to improve the anticorrosion properties of magnesium-lithium (Mg-Li) alloys after blending with eco-friendly silane sol. The chemical structures and morphologies of PANI samples were evaluated by FTIR spectroscopy, UV-Vis-NIR spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). All characterizations indicate that the as-synthesized phosphorized PANI (PANI-PhA) exists in doped emeraldine salt state with net-like structures crosslinked by phosphate carboxyl groups. The conductivity and thermostability of PANI-PhA were better than those of PANI doped with phosphoric acid (PANI-H₃PO₄) and undoped PANI. The anticorrosion properties of PANI/silane sol composite coatings for Mg-Li alloy were tested by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The results prove that the anticorrosion ability of PANI-PhA is the best among the three PANI samples, as shown by a low corrosion current (1.28 × 10^?7 A·cm^?2) and high impedance (5.62 × 10⁶ Ω·cm²). The possible anticorrosion mechanism was proposed based on procedure analysis.     

Inhibition of acrylic acid polymerization by phenothiazine and p-methoxyphenol. II. Catalytic inhibition by phenothiazine

Inhibition of acrylic acid by p-methoxyphenol fits a conventional stoichiometric mechanism but phenothiazine inhibits acrylic acid via a completely different, catalytic cycle which does not depend on the presence of oxygen. We propose that this mechanism may involve a pair of single electron transfer reactions between free radicals, phenothiazine N-radicalcation, and phenothiazine itself, the latter being cyclically regenerated. Arrhenius equations were derived for the rates of disappearance of inhibitor and oxygen in acrylic acid stabilized with phenothiazine and with p-methoxyphenol and also with phenothiazine in the absence of oxygen. The practical implication of high oxygen to p-methoxyphenol consumption ratios is quite important: if commercial acrylic acid (usually stabilized with p-methoxyphenol) is inadvertently heated during storage, the limiting substance determining the onset of polymerization will be the dissolved oxygen and not p-methoxyphenol unless oxygen (air) is being supplied to and dissolved in the liquid at a rate sufficient to overcome the rate of its consumption.     

Electrochemical synthesis of self-doped polyaniline and its use to the electrooxidation of ascorbic acid

Self-doped polyaniline (PAN) film on platinum electrode surface has been synthesized via electrochemical copolymerization of aniline with orthanilic acid (OAA). Fourier transform infrared, UV–Vis, and elemental analysis indicate the formation of the copolymer and that the copolymer has the structure of a head-to-tail coupling of aniline and OAA units. It was found that the internal doping of PAN with OAA can extend the electroactivity of PAN in neutral and even in alkaline media. The obtained self-doped PAN (PAN-OAA)-coated platinum electrode is shown to be a good surface for the electrooxidation of ascorbic acid (AA) in phosphate buffer solution of pH 7. The anode peak potential of AA shifts from 0.63 V at bare platinum electrode to 0.34 V at the PAN-OAA-modified platinum electrode with greatly enhanced current response. A linear calibration graph is obtained over the AA concentration range of 5–60 mM using cyclic voltammetry. Rotating disk electrode voltammetry and chronoamperometry have been employed to investigate the electrooxidation of AA. The PAN-OAA-modified platinum electrode shows good stability and reproducibility.     

Facile synthesis of polyaniline hemispheres in diethyl ether/ice mixture solvent and growth mechanism study

By using the new methodology of synthesis of container structure, we demonstrate the ability to control an improved ice‐templating method to synthesis of polyaniline (PANI) in the form of hemisphere. The influence of the synthetic parameters, such as the concentration of doping‐acid, oxidant, and aniline on the morphologies of PANI structures, has been investigated. It is determined that the doping acid and the second solvent added (such as diethyl ether absolute) have great positive influence on the formation of product's micro‐morphology. The structure and morphology of PANI hemispheres are characterized by Fourier transform infrared (FT‐IR) spectra, X‐ray diffraction (XRD) patterns, energy‐dispersive X‐ray analysis (EDX), optical microscope images, and scanning electron microscope images (SEM). The formation mechanism of hemispheres in this article is well suggested. PANI hemispheres have super performance in sensitivity, time response to NH₃ compared with traditional polymerization at room temperature. This work extends the field of functional materials with complex container structure and offers a new green route to synthesis of hemispherical container structure. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3596–3603, 2010     

Effect of dopant concentration on the catalytic properties of H4SiW12O40 – polyaniline system

Ethanol conversion on polyaniline supported H₄SiW₁₂O₄₀ was investigated at 443 – 483 K. Catalytic activity of the samples expressed as conversion rate per 1 m² exhibits a maximum at H₄SiW₁₂O₄₀ content, equal to about 30 wt.%. The proposed interpretation of these effects is given.     

聚苯乙烯-b-聚丙烯酸模板剂成核段长度对聚苯胺尺寸及性能的影响

以两亲性嵌段共聚物为模板是构筑导电聚合物纳米结构并对其形貌尺寸进行调控的有效方法之一。 嵌段共聚物成核段长度的变化对其胶束化行为有显著影响,进而也会改变受限于其胶束形貌的导电聚合物的形貌尺寸。 形貌尺寸的变化必然导致导电聚合物电化学性能变化。 本文欲通过嵌段共聚物模板诱导实现对聚苯胺(PANI)形貌尺寸的调控并使其电化学性能得到优化,采用可逆加成-断裂链转移自由基聚合(RAFT)法成功合成了嵌段共聚物聚苯乙烯-b-聚丙烯酸PS_x-b-PAA₇₀(x=38、64、101)并以其胶束为“模板”制备了窄相对分子质量分布的PANI。 在成核段(PS)长度较短时,模板诱导形成的棒状PANI颗粒,直径为100~200 nm。当 x=101时PANI呈现空间网状结构,其放电比容量高于其它样品,在电流密度为1 A/g时,其放电比容量可达386.71 F/g。     

Synthesis and characterization of poly (acrylonitrile‐co‐acrylic acid) as precursor of carbon nanofibers

Synthesis of a co‐polymer of polyacrylonitrile (PAN) producing a carbon nanofiber out of PAN and co‐polymer of PAN and comparison between these products were examined. Free‐radical solution copolymerization of acrylonitrile (AN) with acrylic acid (AA) was studied. In this perspective, AA, and AN were used as a precursor for polymerization reactions; then copolymers were synthesized by using ammonium persulfate (APS) as an oxidant and carried in water/dimethylformamide (DMF) mixture. These polymers were used to obtain corresponding electrospun nanofibers. Synthesized P(AN‐co‐AA) was investigated by Fourier transform infrared spectroscopy‐attenuated total reflection (FTIR‐ATR) spectroscopy, and characteristic peaks for AN unit, AA were achieved. Thermal behavior was examined by using differential scanning calorimeter (DSC) and thermal gravimetric analyzer (TGA), and results indicated that addition of monomers to AN unit reduced the Tg value of homopolymer PAN compared to P(AN‐co‐AA), which provides improvement to the cyclization and the formation of a thermally stable aromatic ladder polymer chain formation. In order to prevent the shrinkage and maintain the molecular orientation on nanofiber webs during stabilization, tension was applied to the samples, and thermal oxidation varies at 200–300°C for different duration of times. Surface morphology of the fibers was observed with scanning electron microscope (SEM), and average nanofiber diameter was found 550 nm, and after carbonization it was reduced to 320 nm for homopolymer PAN, and for poly(AN‐co‐AA) average nanofiber diameter was found as 220 nm and reduced to 130 nm, respectively. Copyright © 2016 John Wiley & Sons, Ltd.     

One‐step preparation of solution processable conducting polyaniline by inverted emulsion polymerization using didecyl ester of 4‐sulfophthalic acid as multifunctional dopant

A new one‐step method of preparation of solution processable conductive polyaniline (PANI) is reported using didecyl ester of 4‐sulfophthalic acid (DESPA) as multifunctional material. It consists of inversed emulsion polymerization of aniline in water/chloroform mixture with benzoyl peroxide initiator, maleic acid (MA) as a codopant and DESPA as protonating agent, surfactant, and plasticizer. The resulting product combines reasonable conductivity (ca.0.03 S/cm) with solubility in common solvents such as tetrahydrofuran and chloroform. Elemental analysis together with spectroscopic studies show that the protonation level of emulsion polymerized PANI (0.47 per mer involving one ring and one nitrogen) is very close to that predicted for PANI in the oxidation state of emeraldine (0.5). MA is incorporated into the polymer matrix as a co‐dopant in the ratio 1:4 with respect to the DESPA dopant. PANI‐DESPA‐MA three components system shows a highly ordered, layer‐type supramolecular structure, in which planes of regularly π‐stacked PANI chains are separated by a double layer of dopants. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1051–1057, 2008     

Chemical and electrochemical grafting of polyaniline onto poly(vinyl chloride): synthesis,characterization, and materials properties

We have designed and developed a new strategy for the chemical and electrochemical graft copolymerization of aniline onto poly(vinyl chloride). For this purpose, first phenylamine groups were incorporated into poly(vinyl chloride) via a nucleophilic substitution reaction in the presence of a solvent composed of 4‐aminophenol, potassium carbonate, and dry N,N‐dimethylformamide at room temperature, in order to avoid cross‐linking. The macromonomer obtained was used in chemical and electrochemical oxidation copolymerization with aniline monomer to yield a poly(vinyl chloride)‐g‐polyaniline (PVC‐g‐PANI) graft copolymer. The chemical structures of samples as representatives were characterized by means of Fourier transform infrared and ¹H nuclear magnetic resonance spectroscopies. The electroactivity behaviors of the synthesized samples were verified under cyclic voltammetric conditions. The electrical conductivity and electroactivity measurements showed that the PVC‐g‐PANI graft copolymer has lower electrical conductivity as well as electroactivity than those of the pure PANI. However, the lower electrical conductivity and electroactivity levels in this material can be improved at the price of solubility and processability. Moreover, the thermal behavior and chemical composition of the synthesized graft copolymer were investigated. Copyright © 2016 John Wiley & Sons, Ltd.     

Needleless electrospinning of poly(acrylic acid) superabsorbent: Fabrication,characterization and swelling behavior

In this work, nanofibrous hydrogel has been fabricated from needleless electrospinning of Poly(acrylic acid) (PAA) in an aqueous solution with different concentrations. First, all solution samples were characterized for pH, surface tension, conductivity and viscosity. Next, electrospinnability of the PAA-water dope solution was investigated using the needleless electrospinning technique under constant conditions. Results indicated that the PAA-water solution was not electrospinnable. Therefore, the neutralization of carboxylic groups in the PAA chemical structure using the NaOH solution was investigated to enhance the PAA electrospinnability. Morphology observation revealed that the fiber diameters ranged from 40 to 250 nm and increased with increasing the solution concentrations. Increasing the neutralization degree (10%, 15% and 20% with 50 wt% NaOH solution) led to increase the dope viscosity and conductivity. The resultant nanofibers could be rendered water-insoluble by incorporating 1,4-butanediol diglycidyl-ether in the PAA-water dope solution, then heat-induced crosslinking was performed using a microwave at different curing times (1–5 min) and temperatures (45–105 °C). The nanofibrous hydrogel mat was then characterized by FTIR. The resulting nanofibrous hydrogel showed remarkable water absorption capacity up to 17,000% and 51,000% (within 15 min) in the standard saline solution and distilled water, respectively.     

Effect of synthesis method and buffer composition on the LCST of a smart copolymer of N‐isopropylacrylamide and acrylic acid

Responsive polymers have been the focus of many studies during the past decade because of their ability to change according to environmental stimuli. In this paper, we report on the development of a method to synthesize a pH/temperature‐sensitive linear copolymer, poly(N‐isopropylacrylamide‐ co‐acrylic acid)(poly(NIPAAm‐co‐AAc)), with a molecular weight of about 10⁶–10⁵ Da in water using azobisisobutyronitrile (AIBN) as the initiator. The effects of the following on the lower critical solution temperature (LCST) of the copolymer and homopolymer of NIPAAm were investigated: the type of buffer salts and pH changes of test solutions, molecular weight and concentration of homopolymer/copolymer solutions, and AAc monomer molar feed ratio (mol%). The effects of different synthesis methods on the molecular weight and on the AAc content were also evaluated. The mechanism of action in environments with different pH values is discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Effect of metal phthalocyanines on the synthesis and physicochemical properties of polyaniline

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