Acrylamide Complexes Research Articles

Polymer-Assisted Synthesis, Structure and Magnetic Properties of Bimetallic FeCo- and FeNi/N-Doped Carbon Nanocomposites

Bimetallic FeCo and FeNi nanoparticles attract much attention due to their promising magnetic properties and a wide range of practical applications as recording and storage media, catalytic systems in fuel cells, supercapacitors, lithium batteries, etc. In this paper, we propose an original approach to the preparation of FeCo- and FeNi/N-doped carbon nanocomposites by means of a coupled process of frontal polymerization and thermolysis of molecular co-crystallized acrylamide complexes. The phase composition, structure, and microstructure of the resulting nanocomposites are studied using XRD, IR spectroscopy, elemental and thermal analysis, and electron microscopy data. The main magnetic characteristics of the synthesized nanocomposites, including the field dependences and the ZFC-FC curves peculiarities, are studied. It is shown that the obtained FeCo/N-C nanocomposites exhibit exchange bias behavior at low temperatures. In turn, FeNi/N-C nanocomposites are ferromagnetically ordered.

FeCo@N‐Doped Nanoparticles Encapsulated in Polyacrylamide‐Derived Carbon Nanocages as a Functional Filler for Polyethylene System

AbstractIn this work, using the advantages of Fe and Co nitrates acting as nucleation sites, we polymerized acrylamide (AAm) complexes using frontal polymerization to obtain FeCo alloy/N‐doped carbon composites by converting its original precursor. The results of PAAm coating were found to be extremely useful in suppressing the collapse of the FeCo microstructure during pyrolysis, resulting in a unique hierarchical FeCo@C−N core‐shell nanoparticle architecture encapsulated in PAAm‐derived carbon nanocages. The thermal, mechanical and magnetic properties of the resulting FeCo/C−N filling polyethylene system have been investigated and presented.

Complex formation in the Fe(II)-Fe(III)-acrylamide–water system and chemical models

This paper investigates complex formation in the Fe(II)-Fe(III)-acrylamide-water system. Dependences of oxidative potentials on the concentration and model parameters of iron acrylamide complexes are discussed. Effect of reaction pH on polymerization of acrylamide and applications of polyacrylamide crosslinking reactions are described. At low pH and high temperatures, formation of water-insoluble cross-linked polymers is possible due to creation of imide bridges between the macromolecules (–CO–NH–CO–). Calculations of the formation constants according to their chemical and physical properties such as pH, temperature and ionic strength of the solution are outlined. Chemical models of acrylamide coordination compounds with Fe(III) and Fe(II) at 298.16 K and energy J = 0.5 are shown in this article. A chemical model of the equilibria numerical values of the complexes for oxidized and reduced forms of the metal, the number of protons they contain, the number of coordinated ligands, hydroxyl groups (g, p, s, l and k), are calculated by comparing the slopes of the experimental curves and partial derivative oxidative potentials of concentration variables. Dependences of the Fe(II) and Fe(III) complexes formation on pH for the systems of Fe(II)-Fe(III)-acrylamide-H2O have been determined.

Interactions of acetamide and acrylamide with heme models: Synthesis, infrared spectra, and solid state molecular structures of five- and six-coordinate ferric porphyrin derivatives

The amide functional group is a fundamental building block of proteins, but is also present in several industrial chemicals such as acetamide and acrylamide. Some acetamide derivatives are known to deplete cytoplasmic heme, and some acrylamide derivatives are known to cause porphyria and may activate soluble guanylyl cyclase through a heme-dependent mechanism. We have prepared a representative set of six-coordinate acetamide and acrylamide (L) complexes of iron porphyrins of the form [(por)Fe(L)2]ClO4 (por = TPP (tetraphenylporphyrinato dianion), T(p-OMe)PP (tetrakis(p-methoxyphenyl)porphyrinato dianion)) in 76–83% yields. We have also prepared the five-coordinate derivatives [(OEP)Fe(L)]ClO4 (OEP = octaethylporphyrinato dianion) in 68–75% yields. These compounds were characterized by IR spectroscopy and by single-crystal X-ray crystallography. The molecular structures reveal the monodentate O-binding of the acetamide and acrylamide ligands to the ferric centers, with variable H-bonding exhibited between the acetamide/acrylamide –NH2 moieties and the perchlorate anions. The five-coordinate OEP derivatives exhibit a π-π stacking of their porphyrin macrocycles, with the acetamide complex in the Class I and the acrylamide complex in the Class S groups. These compounds represent the first structurally characterized acetamide and acrylamide adducts of iron porphyrins. Reactions of the six-coordinate derivatives with NO result in the nitrosyl [(por)Fe(NO)(L)]ClO4 derivatives that have been characterized by IR spectroscopy.

Analogies between chemical and biological processes occurring in autowave mode

On the examples of frontal polymerization, tumor growth, and propagation of the nerve impulse, we examined nonlinear phenomena in chemistry and biology. The results of theoretical and experimental studies on the loss of stability of thermal waves of frontal polymerization were presented. The stationarity loss limits for the reactions of epoxide resin curing, polymerization of metal-containing acrylamide complexes, and copolymerization of methyl methacrylate and styrene in the presence of single-walled nanotubes were experimentally studied and theoretically calculated. It was shown that stability of the frontal process waves depends on the heat balance of the exothermic polymerization reaction. Nonlinear phenomena at variation of the polymerization kinetic parameters were studied. The limits of the transition from stationary to nonstationary mode were determined on the basis of experimental data and theoretical calculations. Theoretical study of a diffusion-kinetic model of tumor growth was discussed; the wave nature of the propagation of tumors was shown. The FitzHugh–Nagumo model was studied in view of the diffusion equation; the possibility of formation of the oscillatory modes during the nerve impulse propagation was demonstrated.

Polymer-immobilized rhodium complexes forming in situ: preparation and catalytic properties

We elaborated a method for frontal polymerization of a Rh-containing monomer in the presence of a conventional support to obtain polymer-immobilized hydrogenation catalysts. A hybrid nanocomposite forms during the propagation of a narrow molten zone (first-order phase transition) and is characterized by stable front propagation throughout the reaction volume. The products were characterized by various physicochemical methods and were tested as catalysts in the hydrogenation of cyclohexene, allyl alcohol, and nitrobenzene. The transformation of the X-ray photoelectron spectrum (XPS) on passing from the starting rhodium nitrate complex to its metal monomer (acrylamide complex), polymer, and supported catalyst is described. Native intermediate products were isolated and characterized by XPS.

Fabrication and characterization of metal-core carbon-shell nanoparticles filling an aeronautical composite matrix

Metal nanoparticles (NPs) were prepared from acrylamide complex of iron and nickel nitrates by controlled thermolysis at constant temperature in a self-generated atmosphere and used to fabricate epoxy resin nanocomposites. X-ray diffraction performed on the nanoparticles revealed a metal core/polymeric shell structure for the nanoparticles thermolysed at higher temperature as also confirmed by cross analysis of thermo-gravimetrical and vibrating magnetometer data. Optical microscopy was used to investigate the achieved dispersion of the nanoparticles within the uncured resin and transmission electronic microscopy was used to analyse the morphology and the average dimensions of the nanoparticles. Thermal stability of manufactured nanocomposites was studied by thermo-gravimetric analysis in inert and oxidative conditions, reporting that negligible variations are induced by the presence of nanofillers. A complete thermo-mechanical and fracture characterization was carried out to assess the effect of nanoparticles on final nanocomposite system. A slight increase of the modulus is recorded at room temperature whereas a significant variation is induced for higher temperature. The presence of nanoparticles induces a global increase in the fracture energy of nanocomposite associated to different failure mechanisms. Magnetic data indicate that iron particles based nanocomposites display room-temperature ferromagnetic behaviour with saturation magnetization and coercivity depending on the diameter of the metal core.

Macromolecular Acrylamide Complexes of Rhodium: Synthesis and Characterization

SummarySummary Novel acrylamide complexes of Rh(III) nitrate were synthesized and characterized. They possess the ability to polymerize in the frontal regime in a condensed state as a result of thermal initiation. Polymerization was shown to occur directly in the melting region of a complex at 130−140°C. The synthesis of the acrylamide complex of Rh(III) nitrate on the surface of inorganic supports followed by polymerization and reduction results in the formation of a polymer inorganic composite with inclusions of Rh nanoparticles stabilized by the polymer matrix on the support surface.

Frontal polymerization of acrylamide complex with nanostructured ZnS and PbS: Their characterizations and sensing applications

In the present communication, thermal frontal polymerization (TFP) technique has been employed for the synthesis of ZnS/polyacrylamide and PbS/polyacrylamide nanocomposites. In order to understand the sensitivity of these polymeric nanocomposites towards the liquefied petroleum gas (LPG), the sensing surfaces have been scanned using scanning electron microscope, transmission electron microscope and atomic force microscope. X-ray diffraction reveals the formation of ZnS/polyacrylamide and PbS/polyacrylamide nanocomposites. Solid state pellets have been prepared under uniaxial pressure and temporal variation of electrical resistance has been recorded for different concentrations of LPG at room temperature (27°C). The effect of the surface morphologies on the response of the fabricated device is the focus of the investigation. Better sensitivity and sensor response, small response and recovery times, and long term stability promise to PbS/polyacrylamide as a better LPG sensor in comparison to ZnS/polyacrylamide.

Polymer-matrix nanocomposite gas-sensing materials

A new approach has been proposed for producing nanocomposite gas-sensing materials: in situ preparation of a polymer matrix and metal sulfide or oxide nanoparticles through the frontal polymerization of Co(II), Cd(II), Zn(II) and Pb(II) acrylamide complexes. The composition and structure of the nanocomposites thus obtained have been determined using X-ray diffraction, scanning and transmission electron microscopy, and Raman spectroscopy. The nanocomposites have been tested as room-temperature liquefied petroleum gas sensors.

Local coordination of Co2+ and Ni2+ cations in polyacrylate matrices

Parameters of the local coordination of Co2+ and Ni2+ cations in polymer matrices are determined by XAFS spectroscopy at the K edges of the corresponding elements. Ion-exchange complexes of Ni2+ and polymethacrylate, low-molecular acrylamide complexes [M(CH2=CHC(O)NH2)6](NO3)2 (M = Co or Ni), and products of their thermal polymerization are investigated. The final results are in agreement with the octahedral coordination of M atoms (average distances, 2.10–2.11 (Co-O) and 2.05–2.06 A (Ni-O).

Polymer-assisted synthesis of metallopolymer nanocomposites and their applications in liquefied petroleum gas sensing at room temperature

In this paper, the synthesis of the acrylamide complex of Co (II) nitrate followed by polymerization and formation of a polymer composite with inclusions of Co nanoparticles stabilized by the polymer matrix has been reported. Cobalt polyacrylamide (Co/PAAM) was prepared by the procedure including formation of cobalt acrylamide complex, followed by frontal polymerization and pyrolysis of the polymer. Structural investigations of the materials were carried out by X-ray diffractometer. Surface morphologies were analyzed using scanning electron microscope and nano-structural properties were studied by using high resolution transmission electron microscope and atomic force microscope. Phase transformation temperature was evaluated using a differential scanning calorimeter. The crystallite size of the Co/PAAM was found ∼6nm and confirmed by TEM analysis. Thick films of the metallopolymers were made by screen printing technique and these were investigated with exposition of LPG for measurements of LPG sensing characteristics. Larger variations in resistance were found for Co/PAAM in comparison to Co(NO3)2·(AAM)4·2H2O. The maximum values of the sensitivities were 2.9 and 23.6MΩ/s for Co(NO3)2·(AAM)4·2H2O and Co/polyacrylamide respectively. The reproducibility of the sensor made of Co/PAAM film was found to be 96% after one month of observations, which shows the stability and reliability of the fabricated sensor.

Structural and Thermophysical Properties of Magnetic Beads Containing Metallic Nanocrystallites

Cobalt, iron, nickel and iron carbide nanocrystallites, stabilized within carbon beads, were prepared by the three-step procedure including formation of metal acrylamide complex, followed by frontal polymerization and pyrolysis of the polymer at various temperatures. The beads containing the nanocrystallites exhibit domination of the ferromagnetic ordering. The analysis of calorimetric results allowed estimation of the efficiency of the hyperthermal effect, under the influence of an alternating magnetic field. The XTT tests show that the extracts prepared on the basis of the Fe3C containing beads are nontoxic, whereas these made of the composites containing Co and Ni exhibit negligible cytotoxicity for the test article/vehicle ratios 6.25 and 3.125 mg/ml.

Thermophysical and Magnetic Properties of Carbon Beads Containing Cobalt Nanocrystallites

Ferromagnetic and superparamagnetic nickel nanocrystallites, stabilized in a carbon matrix, were prepared by a three-step procedure including formation of a Ni acrylamide complex, followed by frontal polymerization and pyrolysis of the polymer at various temperatures. It was found that the procedure applied enables fab- rication of magnetic beads containing metallic nanocrystallites embedded in a carbon matrix. The size of the crystallites, their morphology, volume fraction, and magnetic properties can be tailored by the pyrolysis temperature. The size of the crystallites affects their behavior in an external magnetic field, i.e., a heating process is the most effective for a sample pyrolyzed at 873 K. The revealed H n -type dependence of the temperature increase rate, (dT /dt)t=0, on the amplitude of the magnetic field indicates the presence of both superparamagnetic and ferromagnetic particles in all the samples studied since n > 2. For the superparamagnetic particles, the heating mechanism is associated with Neel relaxation. For the lower values of the magnetic field amplitude, H H0 ,t he magnetic hysteresis is the main source of thermal energy losses. The composites con- taining magnetic Ni nanocrystallites entrapped in a carbon matrix can be potentially applied for hyperthermia treatment.

Experimental investigations on liquefied petroleum gas sensing of Cd(NO 3) 2·(AAm) 4·2H 2O and CdS/polyacrylamide synthesized via frontal polymerization

This paper reports an experimental investigations on comparative assessment of CdS/polyacrylamide and Cd(NO 3) 2·(AAm) 4·2H 2O thick films for LPG sensing at room temperature. For synthesis of nanoparticles of CdS in polymer matrix, we used frontal polymerization of cadmium nitrate acrylamide complex Cd(NO 3) 2 (CH 2 CHCONH 2) 4(H 2O) 2 (CdAAm). According to IR spectroscopy in the spectra of polymeric CdS/AAm, there are absorption bands corresponding to stretching vibrations of OH and NH groups. The absence of absorptions bands of the ν (C C) and δ ( CH) at 1580 and 980 cm −1 confirms the assumption of the C C bonds during polymerization. The formation of CdS nanoparticles was proved by X-ray diffractometry. The diffuse diffraction maxima and line broadening indicate that the sample contains nanoparticles. The crystallite size of the CdS/polyacrylamide was found ∼30 nm. Thick films of these metallopolymers were made by screen printing technique on alumina substrate and these were stabilized for 6 h at 80 °C. Further the films were annealed at 450 °C for 2 h. Silver contacts were made on both sides of the films for signal registration, and these films were used as gas sensing elements. Each film was put inside a gas chamber having a gas inlet and an outlet for measurements of LPG sensing characteristics. Variations in electrical resistance of the films with time for different concentrations of LPG were recorded. More variations in resistance were found for Cd(NO 3) 2·(AAm) 4·2H 2O as comparison to CdS/polyacrylamide. The maximum values of the sensitivities was 1.3 and 3.7 GΩ/min respectively, for CdS/polyacrylamide and Cd(NO 3) 2·(AAm) 4·2H 2O for 5 vol.% of LPG. The reproducibility of the sensor made of Cd(NO 3) 2·(AAm) 4·2H 2O after 1 month for 5 vol.% of LPG was found to be 97%.

Thermophysical and Magnetic Properties of Carbon Beads Containing Nickel Nanocrystallites

Ferromagnetic and superparamagnetic nickel nanocrystallites, stabilized in a carbon matrix, were prepared by a three-step procedure including formation of a Ni acrylamide complex, followed by frontal polymerization and pyrolysis of the polymer at various temperatures. It was found that the procedure applied enables fabrication of magnetic beads containing metallic nanocrystallites embedded in a carbon matrix. The size of the crystallites, their morphology, volume fraction, and magnetic properties can be tailored by the pyrolysis temperature. The size of the crystallites affects their behavior in an external magnetic field, i.e., a heating process is the most effective for a sample pyrolyzed at 873 K. The revealed H n-type dependence of the temperature increase rate, (dT/dt) t=0, on the amplitude of the magnetic field indicates the presence of both superparamagnetic and ferromagnetic particles in all the samples studied since n > 2. For the superparamagnetic particles, the heating mechanism is associated with Néel relaxation. For the lower values of the magnetic field amplitude, H < H 0, the relaxation losses dominate whereas for the opposite case, H > H 0, the magnetic hysteresis is the main source of thermal energy losses. The composites containing magnetic Ni nanocrystallites entrapped in a carbon matrix can be potentially applied for hyperthermia treatment.

Reactivity of metal-containing monomers 70. Preparation and magnetic properties of metal-containing nanocomposites

Nanocomposites containing magnetically active nanoparticles stabilized by the carbon-containing matrix formed in parallel were obtained by the polymerization—destruction synthesis. The composition, structure, and magnetic properties of nanocomposites synthesized by the thermal decomposition of unsaturated metal carboxylates and transition metal (CoII, NiII, FeIII) acrylamide complexes were studied by powder X-ray diffraction, scanning and transmission electron microscopy, and Mossbauer spectroscopy. The key macro stages and kinetic features of thermolysis of the metal-containing monomers were identified. The variation of the conditions of thermal transformations allows one to control the magnetic properties of nanocomposites from ferromagnetic to superparamagnetic behavior.

Hybrid polymer-immobilized palladium nanoparticles: Preparation and catalytic properties

A new approach to the synthesis of mixed-type immobilized catalysts was developed: the frontal polymerization of a metal-containing monomer in the presence of a highly dispersed mineral support. The synthesis of an acrylamide complex of Pd(II) nitrate on the surface of SiO2, Al2O3, or C and its subsequent polymerization and reduction resulted in the formation of an organic-inorganic composite that included nanosized Pd particles stabilized by a polymer matrix and an inorganic support. The resulting hybrid nanocomposites are efficient and selective catalysts for the hydrogenation reactions of cyclohexene and alkene and acetylene alcohols.

Thermodynamic characteristics of hydrated acrylamide and polyacrylamide complexes of cobalt nitrate at T → 0 to 380 K

The temperature dependences of the heat capacities of hydrated acrylamide and poly(acrylamide) complexes of cobalt nitrate are studied via high-precision adiabatic calorimetry at 6 to 300–380 K. The energy of combustion is estimated via isothermic calorimetry. This evidence makes it possible to calculate thermodynamic functions Cpℴ(T), Hℴ(T) − Hℴ(0), Sℴ(T), Gℴ(T) − Hℴ(0) at 0 to 300–380 K; the standard enthalpy of combustion, ΔcHℴ; and the thermodynamic parameters of formation, ΔfHℴ, ΔfSℴ, and ΔfGℴ, of monomer and polymer complexes composed of simple compounds at 298.15 K. The results are used for the estimation of enthalpy ΔpolHℴ, entropy ΔpolSℴ, and Gibbs function ΔpolGℴ of bulk polymerization for hydrated acrylamide complexes of cobalt nitrate at 0–300 K.

Tailoring of the Magnetic Properties of Co, Fe and Ni Nanocrystallites

Ferromagnetic or superparamagnetic nanocrystallites, stabilized in carbon matrix, were prepared by the procedure comprising formation of the appropriate metal acrylamide complex, followed by frontal polymerization and pyrolysis of the polymer. The pyrolysis products were in a form of beads, which contained in their volume randomly distributed nanocrystallites. The nanocrystallites had various composition, magnetic properties and sizes ranging from few to tens of nanometers, depending on the element type. Application of this procedure stabilizes the nanostructure and enables processing of nanoparticles within a narrow window of sizes. The magnetic parameters depend on the crystallite size, determined by their chemical composition. The nanocrystallites pyrolysed at 773 K exhibited ferromagnetic properties for Co and Fe, and superparamagnetic behaviour for the Ni. The nanocrystallites can potentially be applied as sensors for tagging the biological substances or for targeted drug delivery.