Synthesis and aqueous solution properties of novel thermosensitive polyacrylamide derivatives

A series of novel thermosensitive polymers were synthesized with acrylamide and thermosensitive macromonomers by radical polymerization in water solution. The structures of the copolymers were characterized by ¹H‐NMR. The effects of the polymer concentration, NaCl concentration, shear rate, and chemical structure on the thermothickening behavior of the polymer solution were investigated by advanced rheometry. The luminous transmittance of the solution with various polymer concentrations was tested by visible spectrometry. The results show that the thermothickening behavior was due to the phase separation of the polymer solution or intramolecular repulsions between the hydrophobic side chains and hydrophilic backbone at high temperatures. Finally, the thermothickening properties of the novel copolymer were studied under conditions simulating an underground oil reservoir. This novel copolymer is expected to be used as an oil‐displacing agent to enhance oil recovery in the future. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 766‐775, 2013     

Hydrophobically modified acrylamide‐based polybetaines. II. Interaction with surfactants in aqueous solution

The interaction of hydrophobically modified (HM) polybetaines with selected small molecule surfactants in aqueous solution was investigated using rheological and surface tension analyses. The polymers included acrylamide‐based, HM polybetaines containing N‐butylphenylacrylamide (BPAM) and specified amounts of sulfobetaine, 3‐(2‐acrylamido‐2‐methylpropanedimethylammonio)‐1‐propanesulfonate (AMPDAPS), or carboxybetaine, 4‐(2‐acrylamido‐2‐methylpropyldimethylammonio)butanoate (AMPDAB); corresponding control (co)polymers lacking BPAM and/or betaine comonomer(s) were also examined for comparative purposes. Low charge density terpolymers exhibited greater viscosity enhancement with the addition of surfactant compared to the high charge density terpolymers. The addition of sodium dodecyl sulfate (SDS) produced the largest increase in solution viscosity, while N‐dodecyl‐N,N,N‐trimethylammonium bromide (DTAB), N‐dodecyl‐N,N‐dimethylammonio‐1‐propanesulfonate (SB3–12), and Triton X‐100 enhanced polymer solution viscosity to a lesser degree. In most cases, the high charge density carboxybetaine terpolymer exhibited diminished solution viscosity upon surfactant addition. The polymers lacking hydrophobic modification showed no detectable viscosity enhancement in the presence of surfactants. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 658–671, 2004     

Aqueous dispersion polymerization of amphoteric polyacrylamide

The terpolymer of acrylamide (AM), dimethylaminoethyl methacrylate methyl chloride (DMC), and acrylic acid (AA) was synthesized with their molar ratio of 70 : 15 : 15 through dispersion polymerization in aqueous solution of ammonium sulfate (AS), using poly(dimethylaminoethyl methacrylate methyl chloride) (PDMC) as stabilizer and 2,2′‐azobis(2‐amidinopropane) dihydrochloride (V‐50) as initiator. The particle size of the terpolymer ranged from 5 to 8 μm and the intrinsic viscosity was from 5.5 to 11.6 dL g^?1. The terpolymer had anti‐ polyelectrolyte effect under low AS concentration, but polyelectrolyte effect with the concentration beyond 10%. Polymerization dispersion with low apparent viscosity, uniform particles, good stability, and high molecular weight terpolymer was obtained in single stage. The effects of varying concentrations of salt, stabilizer, and monomers on particle morphology and intrinsic viscosity were investigated. With increasing concentration of AS and PDMC, the intrinsic viscosity of terpolymer increased, then decreased afterward. However, it increased gradually with increase in monomer concentration. The particle size was enlarged with increasing of AS and monomer concentration and decreasing of PDMC concentration. The optimum condition was the concentrations of salt, stabilizer, and monomers 28%, 3.0%, and 8% to 15%, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and aqueous solution properties of hydrophobically modified polyacrylamide

Hydrophobically modified polyacrylamide (HMPAM) is synthesized by a free radical micellar polymerization method with low amounts of anionic long‐chain alkyl, sodium 9‐(and 10)‐acrylamidostearate (NaAAS), which is derived from a renewable resource material, oleic acid. In this progress, the molar ratio of Sodium dodecyl sulfate (SDS) to NaAAS is adjusted, so polymers with different lengths of the hydrophobic blocks (NH = 3 and NH = 6) are obtained. The copolymers are characterized by ¹H NMR, and the polymer weight and polydispersity are determined by gel permeation chromatography. The solution behaviors of the copolymers are studied as functions of concentrations, pH, and added electrolytes by steady‐flow and oscillatory experiments. The viscosities of these HMPAMs increase enormously above the critical concentration (c*). The sample with longer hydrophobic blocks exhibits better thickening effect. The rheological behaviors of aqueous solutions of HMPAMs are also investigated at different pH and brine environments. Low pH or the presence of brine promotes the intramolecular associating of hydrophobes for the both copolymers in semidilute solutions. The introduction of ionizable carboxylic group on the long hydrophobic side chain significantly influences the aggregation behaviors of the copolymers, leading to unique solution behaviors of the poly(AAm/NaAAS) copolymers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40754.     

Solution properties of ionic hydrophobically associating polyacrylamide with an arylalkyl group

Copolymers of acrylamide, 2‐acrylamide‐2‐methylpropanesulfate (AMPS), and hydrophobic monomer N‐arylalkylacrylamide (BAAM) were synthesized by free‐radical micellar copolymerization. The effects of the copolymer, BAAM, AMPS, and NaCl concentrations and the pH value on the apparent viscosity of the copolymers were studied. The solution viscosities increased sharply when the copolymer concentration was higher than the critical associating concentration. The apparent viscosities of aqueous solutions of poly(N‐arylalkylacrylamide‐co‐acrylamide‐co‐2‐acrylamide‐2‐methylpropanesulfate) (PBAMS) increased with increasing BAAM and AMPS concentrations. PBAMS exhibited good salt resistance. With increasing pH, the apparent viscosities first increased and then decreased. Dilute PBAMS solutions exhibited Newtonian behavior, whereas semidilute aqueous and salt solutions exhibited shear‐thickening behavior at a lower shear rate and pseudoplastic behavior at a higher rate. Upon the removal of shear, the aqueous solution viscosities recovered and became even greater than the original viscosity, but the salt solution viscosities could not recover instantaneously. The elastic properties of PBAMS solutions were more dominant than the viscous properties, and this suggested a significant buildup of a network structure. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 316–321, 2005     

聚丙烯酰胺水溶液的流变特性

通过测定聚丙烯酰胺(PAM)水溶液不同状态下的表观黏度,研究了质量浓度、剪切速率和温度对PAM溶液流变特性的影响。结果表明,在浓度范围1.0～4.0 g/L时,PAM溶液表观黏度随浓度的增加呈线性递增。在浓度范围2.0～4.0 g/L时,PAM溶液表现为假塑性流体特性,其表观黏度随剪切速率的升高而降低,且两者的对数值呈线性关系,非牛顿指数n随稠度系数K的增加而降低;溶液表观黏度随温度的升高而降低,其黏流活化能约为10 kJ/mol。PAM溶液表现为明显的正触变性。     

Electrical conductivity and counterion association of cationic polyacrylamide derivatives in aqueous solution

Equivalent electrical conductivity (Λ) is reported for three series of cationic quaternary ammonium polyacrylamide derivatives with $\hbox{MeSO}_{4}ˆ{‐}$ , Cl⁻, Br⁻ and I⁻ as counterions at 25 °C, the polyion equivalent concentration C ranging from 5.3 × 10⁻⁴ to 6.4 × 10⁻³ N and from 1.0 × 10⁻³ to 1.4 × 10⁻² N. Equivalent electrical conductivity increases with decreasing polyion equivalent concentration, and the sequence of equivalent electrical conductivity Λ of polyelectrolytes for the same series with different counterions in the range of concentration investigated is: $\hbox{MeSO}_{4}ˆ{‐} > \hbox{Cl}ˆ{‐} > \hbox{Br}ˆ{‐} > \hbox{I}ˆ{‐}$ . The plots of the counterion–polyion interaction parameter f and degree of dissociation α of polyelectrolyte versus the polyion equivalent concentration C show that the order of counterion associating or binding to polyions for the same polyelectrolyte series in the range of concentration studied is $\hbox{MeSO}_{4}ˆ{‐} < \hbox{Cl}ˆ{‐} < \hbox{Br}ˆ{‐} < \hbox{I}ˆ{‐}$ . The chemical structures of the polyion have much influence on the Λ, f and α values of the polyelectrolytes. © 1999 Society of Chemical Industry     

Synthesis of crosslinked superabsorbent carboxymethyl cellulose/acrylamide hydrogels through electron‐beam irradiation

A study on the possibility of the preparation of superabsorbent hydrogels based on crosslinked carboxymethyl cellulose polymer and acrylamide monomer through electron‐beam irradiation was carried out. The effects of the irradiation dose and polymer–monomer compositions on the crosslinking density were studied. The hydrophilic properties of the superabsorbent hydrogels were identified by the swelling percentage. The prepared hydrogels had higher swelling in distilled water than in salt solutions. Moreover, the hydrogels exhibited the highest swelling at pH 7. Also, increasing the temperature up to 50°C caused an increase in the swelling. The thermal properties of the hydrogels were characterized with thermogravimetric analysis. The use of the prepared superabsorbent hydrogels for the growth of rice was also investigated through the water‐retention property. The water retention in the soil was enhanced with the hydrogels. Superabsorbent hydrogels based on carboxymethyl cellulose polymer and acrylamide monomer could be considered as water‐managing materials for agriculture and horticulture in desert and drought‐prone areas. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2003–2008, 2007     

Water‐soluble polymers. LXXXIII. Correlation of experimentally determined drag reduction efficiency and extensional viscosity of high molecular weight polymers in dilute aqueous solution

The extensional viscosity for aqueous solutions of high molecular weight poly(acrylamide) copolymers and poly(ethylene oxide) homopolymers was measured using a laboratory‐designed screen extensional rheometer. A Bingham model was developed to estimate the average local polymer coil extensional viscosity (η_coil). A strong correlation was found between the measured η_coil values and the polymer extensional viscosity predicted by a bead‐spring model. The dilute aqueous solution drag reduction was measured with a rotating disk instrument under conditions minimizing the effects of shear degradation. Extensional viscosity and drag reduction measurements were performed in deionized water and in 0.514M sodium chloride. The relative drag reduction efficiency values (Δ) in both solvents were found to strongly correlate with measured η_coil values. This is the first report of the accurate prediction of drag reduction behavior for a wide range of polymer types in various solvents from the independently measured molecular parameters η_coil and [η]C. The often‐used relative drag reduction efficiency expressed as the product of [η]C and Δ can now be replaced by the absolute drag reduction efficiency [η]Cη_coil. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1222–1231, 2001     

Encapsulation and controlled release in polyacrylamide hydrogels

A novel host–guest system was developed by the encapsulation of simple organic guest molecules in the hydrophilic molecular architecture of crosslinked polyacrylamide hydrogels. The crosslinking agents used for the preparation of the host systems were hexanediol dimethacrylate (HDDMA) and divinyl benzene (DVB). This enabled us to construct hydrogels with different hydrophobic–hydrophilic equilibria. The model guest system used for the studies was benzoic acid. The selections gave simple but excellent host–guest systems with fine polar–apolar balancing. Polyacrylamide hydrogels with encapsulated benzoic acid were prepared with varying crosslink densities (5, 10, 15, and 20 mol %) by the solution polymerization technique. The rate of release of the host from the host–guest assembly was studied in different swelling conditions. The rate of release depended on the interaction forces between the polymer and the solvents. Polar forces, dispersion forces, and hydrogen bonding all played a vital role. The swelling behavior of the host‐polymer system and the host–guest assembly was analyzed and compared by the Flory–Rehner method. The amount of benzoic acid encapsulated in the DVB‐crosslinked polymer was higher than in the HDDMA‐crosslinked polymer, and the rate of release was in the order 5 > 15 > 10 > 20% for the DVB‐crosslinked polymer. The rate of release for the HDDMA‐crosslinked host–guest assembly was in the order 10 > 5 > 15 > 20%. These results were in excellent agreement with those of the Flory–Rehner analysis of the swelling properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1816–1824, 2004     

Swelling behavior of poly(acrylamide)/clay nanocomposite hydrogels in acrylamide aqueous solution

The swelling behaviors of poly(acrylamide) (PAAm)/clay nanocomposite hydrogels (hereinafter abbreviated as NC gels) in acrylamide (AAm) aqueous solution have been investigated. As‐prepared PAAm/clay hydrogels (S‐M gels) were posttreated by immersing them in AAm aqueous solution. It was found that the swelling ratio of the NC gels increased greatly when the concentration of the solution is below a critical concentration (c*), whereas the gels were disintegrated in the solution when the concentration of the solution is above the c*. Some disc‐like particles were found in the AAm solution accompanying with the unusual swelling behaviors. This unusual swelling behavior is resulted from the change of network structure of the NC gels in AAm aqueous solution, which was further convinced by transmission electron microscopy and element analyses. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Evaluating the performance of a portable water–mist fire extinguishing system with additives

This study investigates how high‐pressure water–mist system discharge methodologies influence the fire extinction performance for pan pool fires and the corresponding mechanisms of restraining fire. The fire source is a pool‐fire burner. Fine water spray is injected using a portable device. The additive in the water–mist is neither toxic nor corrosive. All the tests are regarded as fuel controlled. The fire test parameters are fuel type, nozzle discharge angle, and additive solution volume. The fuels used are heptane, gasoline, and diesel. Nozzle discharge angles are 30, 45, and 60° with respect to the ground. Additive solution volumes are 0% (pure water), 3, 6, and 10%. Test results indicate that the nozzle discharge angle and additive solution volume in a water–mist fire extinction system play a significant role. Fire extinguishing efficiency is influenced by mist effects and the additive. Furthermore, the water–mist system can reduce radiation and can provide good protection for operators using portable fire extinguishing equipment. Copyright © 2008 John Wiley & Sons, Ltd.     

Enhancing rheological properties of hydrophobically associative polyacrylamide aqueous solutions by hybriding with silica nanoparticles

Organic/inorganic hybrid aqueous solutions were prepared by mixing silica nanoparticle suspension and hydrophobically associating polyacrylamide (HAPAM) solution, and their rheological behaviors were examined in both pure water and brine in comparison with HAPAM. It was found that HAPAM/silica hybrid exhibits viscosity enhancement in aqueous solution and better heat‐ and salt‐ tolerances than HAPAM. Meanwhile, their long‐term thermal stability is also improved. Cryo‐TEM observation reveals that a reinforced three‐dimensional network structure of HAPAM/silica hybrid is formed. These improved properties are attributed to the formed hydrogen bond between carbonyl groups in HAPAM skeleton and silanol functionalities in silica nanoparticles in the hybrid system, and the silica nanoparticles in the hybrid act as physical crosslinkers between macromolecules. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40876.     

Superabsorbent hydrogel based on modified polysaccharide for removal of Pb2+ and Cu2+ from water with excellent performance

This contribution describes the absorption percentage of Pb²⁺ and Cu²⁺ from water by a superabsorbent hydrogel matrix (SH) made from an anionic polysaccharide copolymerized with acrylic acid (AAc) and acrylamide (AAm). Metal‐absorption tests, upon sequential pH variation, indicated that the SH has pH‐sensitivity for the absorption of both metals from solution, attributed to the functional ionic groups (? COOH) present in the AAc and arabic gum (AG) segments. At the pH 5.0, the SH exhibited good absorption capacity: 73.10% for Pb²⁺, 81.99% for Cu²⁺ in water and 63.64% for Pb²⁺, and 76.67% for Cu²⁺ in saline water with 0.1 mol kg^?1 ionic strength. A replicated 2² full factorial design with a central point was built to evaluate the maximum absorption capacity of the metals into the SH. It was found that both the interaction and main effects of the pH and the initial concentration of metal solution on absorption percentage of the metals were statistically significant. Surface response plots indicated that the absorption capacity of both metals into the SH may be appreciably improved by using the solutions with lower initial concentration of metal and with higher pH values. Metal‐absorption results demonstrated that the SH is a convenient material for absorption of Pb²⁺ and Cu²⁺ from pure aqueous and saline aqueous environments. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Fabrication and properties of superabsorbent complex gel beads composed of hydrolyzed polyacrylamide and chitosan

A novel method for preparing complex beads composed of hydrolyzed polyacrylamide (HPAM) and chitosan, based on the electrostatic attraction between ? COO^? of HPAM and Al³⁺ and between ? COO^? and ? NH₃⁺ of chitosan, was established. In the two‐stage crosslinking process, first Al³⁺ was used as a crosslinking agent for the crosslinking of HPAM molecules, which were used as the skeleton structure of the gel beads. In the second stage, chitosan diffused into the skeleton structure. The gel beads were characterized with scanning electron microscopy, inductively coupled plasma mass spectrometry, Fourier transform infrared spectroscopy, and thermogravimetric analysis. There was a chitosan component in the gel beads, and these gel beads had porous and rough surfaces. The swelling properties of the HPAM–chitosan gel beads were measured in water, in acidic, neutral, and alkaline buffers, and in different saline solutions. The swelling ratio was as high as 3675 g/g in water and 170 g/g in a 0.15 mol/L NaCl solution. The beads showed pH sensitivity in buffers of different pH values and salt sensitivity in different saline solutions. The order of the equilibrium absorbency of the gel beads in different saline solutions was Na⁺ > K⁺ > Mg²⁺ > Ca²⁺ > Al³⁺. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal and swelling studies of hydrophobically modified polyacrylamide hydrogels

Hydrophobically modified polyacrylamide hydrogels were prepared by polymerizing acrylamide, using n‐butyl acrylate and 2‐ethyl hexyl acrylate as comonomers and dimethyl formamide as a solvent. We report here for the first time that the Alfred Q‐e reactivity ratios are matching with the experimental value (elemental analysis result) for the terpolymer hydrogel systems. Differential scanning calorimetry (DSC) thermograms of the hydrogel samples revealed two endothermic transitions, one near 0°C, corresponding to the melting transition of ice and another above ambient temperature. This high temperature transition is due to the rearrangement of water molecules engaged in hydrophobic hydration surrounding the hydrophobic groups (alkyl side chains). This depends on the type of hydrophobic groups and the gel compositions. Swelling and deswelling studies of the gels were performed using various solvents such as water and isopropyl alcohol. An abnormally high swelling and deswelling behavior was observed in the homopolymer gels and the gels with low amount of hydrophobic comonomers. This could be attributed to the more intramolecular cross‐linked structure formed during synthesis in organic solvent. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

PVA/PAA thermo‐induced hydrogel fiber: Preparation and pH‐sensitive behavior in electrolyte solution

The preparation of thermo‐induced hydrogel fibers composed of poly(vinyl alcohol) and poly(acrylic acid) is presented. The hydrogel fiber was prepared by extruding the spinning dope from in situ polymerization of acrylic acid in the presence of PVA into a coagulating bath of saturated ammonium sulfate aqueous solution. The network was formed by thermally heating the dried fibers under vacuum. The final hydrogel fibers exhibit pH‐sensitive behavior and show a hysteresis loop in the pH range from 3.0 to 12.0. The pH value, at which the swelling elongation ratio of the fiber had a jump, shifted to a lower value with increasing PAA content within the network. Increasing the heating temperature and time for the fibers, decreased the swelling elongation ratio, and the jump point pH shifted to higher pH value. The oscillatory swelling/contracting behavior of the hydrogel fiber exhibited a good reversible pH‐responsive property. Transmission Electron Microscopy (TEM) showed that PVA and PAA have good compatibility and give a relative independent interpenetrating network. Scanning Electron Microscopy (SEM) showed that in the surface of the fibers there were microholes and ditches due to some diffusion of PAA into the coagulating solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2423–2430, 2002     

Dissolution and stability of chitosan in a sodium hydroxide/urea aqueous solution

Medium‐molecular‐weight chitosan (MMWC; 157.5 kDa) and low‐molecular‐weight chitosan (LMWC; 53.4 kDa) samples were dissolved in an NaOH/urea solution by freeze–thaw treatment. The factors affecting dissolution were optimized, and the stability of chitosan in the produced solution was investigated. NaOH and urea concentrations of 2 and 0.67 mol/L, respectively, and a treatment temperature of ?18°C were optimized as the dissolving conditions. MMWC and LMWC could be completely dissolved in the 2 mol/L NaOH/0.67 mol/L urea solution after six and five cycles of freeze–thaw treatments, respectively. Dissolution and storage in the 2 mol/L NaOH/0.67 mol/L urea solution slightly increased the deacetylation degree of chitosan and slightly decreased the molecular weight. The solution stability of LMWC was better than that of MMWC. MMWC tended to form a gel during storage. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39819.     

Preparation of polyacrylamide aqueous dispersions using poly(sodium acrylic acid) as stabilizer

High‐solids, low‐viscosity, stable polyacrylamide (PAM) aqueous dispersions were prepared by dispersion polymerization of acrylamide in aqueous solution of ammonium sulfate (AS) using poly (sodium acrylic acid) (PAANa) as the stabilizer, ammonium persulfate (APS) or 2,2′‐Azobis (N,N′‐dimethyleneisobutyramidine) dihydrochloride (VA‐044) as the initiator. The molecular weight of the formed PAM, ranged from 710, 000 g/mol to 4,330,000 g/mol, was controlled by the addition of sodium formate as a conventional chain‐transfer agent. The progress of a typical AM dispersion polymerization was monitored with aqueous size exclusion chromatography. The influences of the AS concentration, the poly(sodium acrylic acid) concentration, the initiator type and concentration, the chain‐transfer agent concentration and temperature on the monomer conversion, the dispersion viscosity, the PAM molecular weight and distribution, the particle size and morphology were systematically investigated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009