Acrylamide-acrylic Acid Copolymers Research Articles

Influence of type and particle size of superabsorbent polymer on early water distribution and internal curing zone properties of cement paste

The types of commercial superabsorbent polymer (SAP) mainly include ionic-SAP acrylic acid (AA) and nonionic-SAP acrylamide-acrylic acid copolymer (AM), which have different particle sizes due to the limited preparation methods. This study used 1H low-field NMR to clarify the influence of type and particle size of SAP on the water distribution of cement paste. Backscattering electrons and nanoindentation were used to quantitatively analyze the area, porosity, and micromechanical properties of internal curing zone. Finally, void system analysis, compressive strength, and autogenous shrinking were systematically studied. The results indicate that the water absorption and retention capacity of AM in cement paste increase with the increase of particle size, and the area of internal curing zone also increased. As the area of internal curing area increases, the autogenous shrinkage of cement paste significantly decreases. The internal curing effect reduces the unhydrated cement content and increases the high-density C–S–H content of internal curing zone, thereby improving the micromechanical properties and to some extent offsetting the decrease in mechanical properties caused by voids. However, larger particle size AM forms larger void and higher air content, leading to a further decrease in strength. Ionic-SAP AA releases a large amount of water before final setting, weakening internal curing effect and reducing the area of internal curing zone. In addition, the early release of water leads to an increase in the local water-cement ratio, which increases the porosity and low-density C–S–H content of internal curing zone, thereby reducing the micromechanical properties.

Comparison of Structural, Water-Retaining and Sorption Properties of Acrylamide-Based Hydrogels Cross-Linked by Physical and Chemical Methods.

Two series of hydrogels based on acrylamide and its copolymers with acrylonitrile and acrylic acid were synthesized by two cross-linking methods - chemical (using N,N'-methylene bis-acrylamide) and physical (using montmorillonite (MMT)) ones. The structure of the gels was characterized by Fourier Transform Infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The swelling and sorption properties were analyzed as a function of both the monomer composition and the cross-linking method. The shift of the band corresponding to Si-O (995-1030 cm-1 ) confirmed the formation of intercalation structures for MMT-cross-linked gels. Moreover, physically cross-linked gels demonstrated a non-monotonic dependence of the swelling degree on the MMT concentration, and acrylamide-acrylic acid copolymer MMT-cross-linked gels showed pH sensitivity and the highest swelling degree of 150 g/g. The highest sorption capacity towards cadmium(II) ions was demonstrated by acrylamide-acrylic acid copolymer gels, both covalently cross-linked (30 mg/g) and MMT-cross-linked (8.9 mg/g).

Синтез, структура и особенности формирования бифазных гибридных композиций на основе бентонита

The synthesis, structure and features of the formation of biphasic hybrid polymer compositions based on natural ionite (bentonite – BT), its intercalated complex (ICC) with a solid solution of copper ferrocyanide K4-хCux[Fe(CN)6] and a synthetic rare cross-linked acrylamide-acrylic acid copolymer were studied. The mechanism of formation of biphasic intercalated and percolated structures was analyzed by means of X-ray diffraction, X-ray fluorescence analysis, IR-Fourier spectroscopy and stress-strain curves. It is shown that the impregnation of the mineral bentonite filler into the polymer matrix, including its intercalated complex {BT:K4-xCux[Fe(CN)6]} is accompanied by an increase of non-uniformity of the structure of the hybrid composite material. It has been established that the main factor characterizing the deformation stability of the composite is the adhesive strength at the interface between the mineral filler and the polymer matrix. Under uniaxial tension of the P[AA-AA]{BT} composition and the percolated complex P[AA-AA]{BT:K4-xCux[Fe(CN)6]} their internal structure is rearranged resulting in stretching of agglomerates of solid fillers along polymer chains, which is determined by the adhesion force between polymer chains and mineral particles at the phase boundary. It is proposed to consider such biphasic hybrid composite materials as a promising class of interpenetrating networks with valuable applied properties.

Determination of Swelling Behavior and Mechanical and Thermal Resistance of Acrylamide-Acrylic Acid Copolymers under High Pressures and Temperatures.

Unwanted water production is a serious problem accompanying oil extraction especially in oil-fractured reservoirs. An effective approach to tackle this issue is to utilize gels as a blockage agent. In this paper, an effective series of preformed particle gels (PPGs) was synthesized by a free radical copolymerization of acrylamide and acrylic acid [poly(AAm-co-AA)] copolymers. The key factors of synthesis experiments, gelation time, drying behavior, swelling capacity (in CaCl2·2H2O, MgCl2·6H2O, BaCl2·2H2O, KCl, NaCl, and LiCl saline solutions with 200,000 ppm concentration and pH from 3 to 8), and mechanical and thermal resistance of the synthesized PPGs (with a homemade apparatus) were elucidated. Laboratory results revealed that the prepared PPG sample 1 (9.65 mole ratio of AAm/AA and 6 mol % of MBA) would be a good candidate for controlling water in oil and gas reservoirs with a salinity, pressure, and temperature of up to 200,000 ppm, 300 bar, and 170 °C, respectively, and pH values ranging from 3 up to 8.

Poly (acrylamide acrylic acid)/Baghouse dust magnetic composite hydrogel as an efficient adsorbent for metals and MB; synthesis, characterization, mechanism, and statistical analysis

Steel manufacturing waste-based magnetic composite hydrogel was fabricated. Acrylamide-acrylic acid copolymer (AA) was intercalated to baghouse dust (BHD) to obtain (AABHD) composite. The synthesized AABHD composite was used for the removal of Pb (II), Cd (II), and MB from aqueous media. The AABHD composite was characterized using SEM, BET, XRD, TGA, FTIR, XPS, and zeta potential. The impact of various parameters on the adsorption performance of the AABHD hydrogel for MB, Cd (II), and Pb (II) was evaluated. The experimental kinetics of MB and metals followed the second-order model, where film diffusion was the dominating mechanism. The isotherm study revealed that equilibrium results of MB follow Dubinin-Radushkevich (D-R), while metals were well described by Freundlich. AABHD exhibited maximum adsorption efficiencies of 96, 98, and 99 percent and capacities of 503, 236, and 476 mg/g for MB, Cd (II), and Pb (II), respectively. The thermodynamic outcome indicated spontaneous and favorable adsorption of MB and metals. The regeneration study verified the high reusability of the AABHD composite for MB and metals. The obtained findings showed that the AABHD could be efficiently employed for the simultaneous elimination of MB and metal ions from wastewater.

Molecular dynamic simulation of core–shell structure: study of the interaction between modified surface of nano-SiO2 and PAMAA in vacuum and aqueous solution

The interaction between acrylamide acrylicacid copolymer (PAMAA) and the modified surface of nano-SiO2 is investigated using the molecular dynamic (MD) simulation. The binding energies (Ebinding) of interface, the concentration profiles of PAMAA and functional groups (carboxyl and acylamino) of corresponding model, the mean square displacements (MSD) and diffusion coefficients (D) of PAMAA in four systems with different modifiers are all calculated at 325 K in vacuum. Vinyl trimethoxy silane (VTEOS) shows best modification effect in the systems mentioned above. Furthermore, the effects of temperature on the interaction between VTEOS modified surface of nano-SiO2 and PAMAA are studied at 300, 325, 350, 375 and 400 K in aqueous solution. Interesting results show that, water molecular layer reduces with the increase of temperature, and then improves the interaction between PAMAA and VTEOS modified surface of nano-SiO2. The corresponding Ebinding of interface, the radial distribution functions (RDF) of carbon atoms on the surface and oxygen atoms of water molecules, the concentration profiles of PAMAA on the surface of nano-SiO2, the MSD and D of PAMAA are all studied seriously to find the reason of this counterintuitive phenomenon.

Preparation of Nano Triblock Co-polymer for Desferoxiamine Delivery and Cross-Linked Copolymer for Iron Overload Disease

Some IPNs and copolymer were prepared at different ratios from bisacryl amide as crosslinking agent by Redox polymerization. These IPNs (polyacrylamide –poly ethylene imine); (polyacrylamide-poly electrolyte) and poly (acrylamide-acrylic acid) copolymer are examined by UV-VIS spectrophotometry method to determine their ability for linking with iron ions that are prepared with standard solution employed for this purpose. The results, indicate that the copolymer prepared from (AcAm:AcAc) with 20% (wt/wt) from bisacrylamide has the ability of removing the iron ions from the solution. The swelling ratio for the prepared IPNs and copolymers was studied as a function of time at different pH (1.2, 8.4) and distilled water; the obtained data show that the swelling ratio was increased with increasing the pH. The morphology of copolymers was performed by scanning electron microscopy (SEM) to show the pore size. A new triblock copolymer of (Polylactide-Pluronic127-Polylactide) is synthesized by ring opening polymerization using (DUB) Diazabicyclo-[5.4.0]-udec-7-ene as a catalyst. The triblock copolymer is characterized 1HNMR. Semi IPNs from triblock copolymer with acrylamide was prepared to use as a polymer drug delivery with Desferriox aminemethanesulphate (Iron overload chelating drug). The SEM for this semi IPN shows the nano structure due to the regular orientation of lactide fibers. Desferoxiamine release study as a function of time at pH 1.2 and 8.4 for 24 hours with semi IPNs coated with tetramethylourea and without coating was also carried out. The releasing studies show that the rate of releasing at GIF is larger than SGF.

Impregnation of polymers with 2,2,6,6-tetramethyl-4-oxo-piperidine-1-oxyl (TEMPONE) paramagnetic probe in sub- and supercritical CO2

The spin probe method is used to study the impregnation of polycarbonate (PC) based on bisphenol A, polyethylene oxide (PEO), and crosslinked acrylamide–acrylic acid copolymer (PAA) with organic molecules in sub- and supercritical CO2 media. Electron spin resonance (EPR) data show that, at 196 bar and 307 K, 2,2,6,6-tetramethyl-4-oxo-piperidine-1-oxyl (TEMPONE) paramagnetic spin probe molecules penetrate into the PC and PEO matrices, which are, respectively, in the glassy and elastic states under normal conditions. The degree of impregnation of PAA under these conditions is negligibly small. Estimates of the local concentration of probe molecules show that, in the PEO matrix, TEMPONE is distributed much more uniformly than in the PC matrix. Analysis of the effect of temperature on the shape of the EPR spectra of the radical in the polymer matrix shows that, under the same conditions, the mobility of TEMPONE molecules in the PEO matrix is much higher than in the PC matrix. The results suggest that the spin probe method is promising for studying the characteristics of macro- and micro-processes in polymer–supercritical fluid solvent–organic molecule ternary systems.

Features of the foaming of acrylamide-acrylic acid copolymers

The processes that occur during the processing and foaming of thermosetting composites based on a random copolymer of acrylamide and acrylic acid—softening, foaming, and curing of the copolymer—are studied with the use of methods of chemical kinetics, Fourier transform infrared spectroscopy, and thermomechanical analysis. The above processes are coordinated with respect to time and temperature; prognostic methods for calculating the dynamics of these processes and the properties of foam materials as functions of the composition of the original foam-forming composite and the foaming conditions are proposed.

Fluorogenic detection of Hg2+, Cd2+, Fe2+, Pb2+ cations in aqueous media by means of an acrylamide-acrylic acid copolymer chemosensor with pendant rhodamine-based dyes

A monomer 1-acrolyl-2-rhodamine 6G hydrazide (AR6GH) was synthesized by the heterogeneous reaction of acryloyl chloride with rhodamine 6G hydrazide (R6GH) and characterized by 1H NMR, FTIR and elememtal analyses. Then it was micellar copolymerized with acrylamide (AM), acrylic acid (AA) to obtain a water-soluble fluorescent copolymers (poly(AM-AA-AR6GH)) which were characterized by the method of FTIR and 1H NMR. The viscosity average molecular weight Mη– of poly(AM-AA) and poly(AM-AA-AR6GH)s were 1.76 × 106, 8.58 × 104 and 7.68 × 104 g/mol, respectively. The fluorescent characteristic of the aqueous solutions of copolymers was investigated both in varied pH and in the presence of metal cations. The poly(AM-AA-AR6GH) was found to be a selective chemosensor for Hg2+, Cd2+, Fe2+, Pb2+ ions. Obvious fluorescence enhancement was due to the photophysical response of the copolymer to the presence of Hg2+, Cd2+, Fe2+, or Pb2+ ions. In addition, the ability of the copolymer to detect different metal cations (Ag+, Ba2+, Co2+, Cd2+, Cr3+, Cu2+, Fe2+, Fe3+, Hg2+, K+, Mg2+, Mn2+, Na+, Ni2+, Pb2+, Zn2+) in aqueous solution was studied. The results suggest that copolymer may offer potential application for sensors of Hg2+, Cd2+, Fe2+, or Pb2+ ions in aqueous solution.

Rheological Study of Polymer--Colloid Complexes of Aluminoxane Particles with Weakly Charged Polyelectrolytes in Semidilute Aqueous Solutions

Viscoelastic properties of hydrogels based on polymer-colloid complexes of aluminoxane particles with acrylamide-acrylic acid copolymers were studied. Rheometric measurements were performed with an MFR 2000 Fourier microrheometer (GBS, Australia) under the regime of oscillating loads with the use of the dynamic mechanical analysis. It is shown that, with copolymer concentrations above the crossover point, the phase angle decreases abruptly; that is, the elastic characteristics of the gels decline. The maximum elastic properties of the gels for all copolymers are attained at the molar ratio of reagents Z ? 1. The effect of strain rate on relaxation processes in the gels was investigated. It is found that, at low strain rates, irreversible deformations (flow) can take place, and with an increase in frequency, the strength of physical networks formed with participation of aluminoxane particles tends to increase.

The Effect of Composition of Copolymeric Hydrogels on Their Physicochemical Parameters

Physicochemical characteristics of gel systems based on slightly cross-linked acrylamide-acrylic acid copolymers were studied and their dependences on such parameters as the cross-link density, the monomer ratio, and the total content of the monomers in a hydrogel were determined. A burn-healing hydrogel material developed on the basis of this study is nontraumatic, transparent; it is characterized by a high absorption capacity with respect to wound exudates and a delayed release of incorporated drugs.

Aqueous solutions of acrylamide-acrylic acid copolymers: stability in the presence of alkalinoearth cations

The interactions between acrylamide-acrylic acid copolymers and alkalinoearth cations were studied by many different techniques, as functions of various parameters: composition of the copolymer and distribution of the acrylic units along the chain; pH; temperature; ionic strength. In a first step, the phase diagrams were established and reveal ranges of polymer and salt concentrations where phase separation occurs. In a second series of experiments, the change in the chain conformation and the aggregation phenomena were investigated by viscosimetry and light scattering. It sorts out that at low enough polymer and salt concentrations (inside the solubility domain), it is possible to get a variation of the intrinsic viscosity of the polymer as a function of calcium concentration and charge parameter of the polymer consistent with previous literature results obtained in the presence of sodium if a binding term depending on the nature of the ion is taken into account. At higher polymer and calcium concentration, high Huggins constants and large increases of scattered intensity reveal the formation of aggregates, which are attributed to intermolecular bridges. The third series of experiments (conductimetry and densimetry) were carried out to characterize the ion-polyion interactions. Finally, the phase separation is discussed in light of the other results, using some simple association models.

Electrochemical Characterization of Enzyme Electrodes Mediated by Ferrocene-Containing Acrylamide-Acrylic Acid Copolymers

Electrochemical Characterization of Enzyme Electrodes Mediated by Ferrocene-Containing Acrylamide-Acrylic Acid Copolymers

Light scattering peaks from aqueous solutions of acrylamideacrylic acid copolymers

AbstractAqueous solutions of acrylamide‐acrylic acid copolymers of high molecular weight have been investigated by light scattering. It was shown that a scattering peak can be obtained if the samples used have been prepared by alcaline hydrolysis of polyacrylamide and if the solutions are filtered and sonicated. In the range of the lower concentrations, the position of this peak, q*, is found to vary with the polymer concentration C, as C1/3, and to be independent of the charge density. The addition of very small amounts of salt provokes the disappearance of the peak. A phase diagram (charge density versus concentration of the polymer) has been established. It shows that these experiments were carried out in a concentration range intermediate between the dilute and the semidilute regimes (transition regime). The experimental scaling laws however correspond to the theoretical predictions for the dilute regime. Moreover, the q* values are much lower than those calculated by the random phase approximation theories.

Effects of Substrate Hydrophobicity on Polyacrylamide Adsorption

The adsorption of nonionic and anionic polyacrylamides in porous media has been studied as a function of substrate hydrophobicity. The adsorption of nonionic polyacrylamide was found to increase with substrate hydrophobicity, being lower on quartzitic sand particles (400 μg/m2) than on the same particles rendered hydrophobic by treatment with hexamethyldisilazane, a short-chain silane (490 μg/m2), or octadecyltrichlorosilane (C18), a highly reactive, long-chain silane (720 μg/m2). The same trend was observed with other siliceous substrates and their C18-treated counterparts. When the C18-treated sand particles were in turn rendered hydrophilic by adsorption of sodium dodecyl sulfate or polyethylene glycol, then polyacrylamide adsorption almost vanished. These effects are interpreted in terms of a competition between substrate/monomer and substrate/solvent (water) interactions. The adsorption of anionic polyacrylamides (acrylamide-acrylic acid copolymers) on quartzitic and C18-treated sand particles has also been measured for different solution ionic strengths, pH's, and polymer ionic (acrylic acid) compositions and distributions along the chain. As with nonionic polyacrylamide, adsorption was significant and increased with substrate hydrophohicity when electrostatic long-range interactions were not predominant, e.g., at low pH or high salinity. For significant electrostatic interactions, however, the inverse trends were observed: adsorption levels were low and decreased from quartzitic to C18-treated sands. The origins of such repulsion between polyelectrolyte and hydrophobic substrate are discussed.

Rheological studies of the gelation of aqueous solutions of acrylamide-acrylic acid copolymers in the presence of chromium chloride

The gelation kinetics of aqueous solutions of acrylamideacrylic acid copolymers in the presence of chromium ions was studied with different rheometers. The gel time is found to vary with the principle of the apparatus because of a low shear dependence of the elongation of the macromolecules. The variations of the gel time with the experimental conditions of the gel preparation were investigated and we conclude that the gelation is governed by the oligornerization kinetics of the chromium ions which are instantaneously, complexated by the carboxylate groups of the polymer. The variation laws of the gel time and of the elastic modulus with chromium and polymer concentrations, temperature and ionic strength are in qualitative agreement with the structure of the temporary network of the semi-dilute solutions of these copolymers.

Potentiometric titration of acrylamide-acrylic acid copolymers: Influence of the concentration

Potentiometric titrations of acrylamide-acrylic acid copolymers of high molecular weight were made at various polymer concentrations, C p, and ionic strengths, I. At a given pH, the ionization degree of the carboxylate groups is found to increase when C p and I increase. In the absence of salt and for a fraction τ of acrylic units in the polymer, the values of p K a at different C p lie on a single curve as a function of ( ∞C p − 1 3 ) for a given τ. It is found that p K a obtained for the various values of C p is a polynomial function of τ 1 2 C p − 1 3 .

Interactions between aluminium ions and acrylic acid-acrylamide copolymers in aqueous solution: 3. Influence of ionic strength on gelation and phase separation

Phase separation and gelation of the aqueous solutions of acrylamide-acrylic acid copolymers in the presence of aluminium chloride are studied as a function of pH and ionic strength. At pH 7, only phase separation is observed as a flocculation of aluminium hydroxide particles by polymer bridges, but because of their small positive residual charge the phenomenon is partially due to electrostatic interactions and consequently depends on the ionic strength of the solution. At pH 5, gelation attributed to the presence of polycations Al 3+ 13 occurs for values of the polymer charge which increase with increasing ionic strength. A qualitative model is proposed to define the conditions and the limits of gelation in such systems.

Effect of the carboxylate group distribution on potentiometric titration of acrylamide-acrylic acid copolymers

the potentiometric behavior of acrylamide-acrylic acid copolymers is discussed as a function of their method of preparation: base hydrolysis of polyacrylamide or radical copolymerization. The values of pK0 (the intrinsic pK at zero degree of ionization) and the variations of pKa versus the ionization degree are found to depend on the origin of the polymers and such differences are qualitatively attributed to significant discrepancies in the carboxylate group distribution.