Hydrophobically Associating Polyacrylamide Research Articles

Hydrophobically Associating Polyacrylamide “Water-in-Water” Emulsion Prepared by Aqueous Dispersion Polymerization: Synthesis, Characterization and Rheological Behavior

The hydrophobically associating polyacrylamide (HAPAM) is an important kind of water-soluble polymer, which is widely used as a rheology modifier in many fields. However, HAPAM products prepared in a traditional method show disadvantages including poor water solubility and the need for hydrocarbon solvents and appropriate surfactants, which lead to environmental pollution and increased costs. To solve these problems, we reported a novel kind of HAPAM "water-in-water" (w/w) emulsion and its solution properties. In this work, a series of cationic hydrophobic monomers with different alkyl chain lengths were synthesized and characterized. Then, HAPAM w/w emulsions were prepared by the aqueous dispersion polymerization of acrylamide, 2-methylacryloylxyethyl trimethyl ammonium chloride and a hydrophobic monomer. All these emulsions can be stored more than 6 months, showing excellent stability. An optical microscopy observation showed that the particle morphology and the particle size of the HAPAM emulsion were more regular and bigger than the emulsion without the hydrophobic monomer. The solubility tests showed that such HAPAM w/w emulsions have excellent solubility, which took no more than 180 s to dilute and achieve a homogeneous and clear solution. The rheology measurements showed that the HAPAM association increases with a hydrophobe concentration or the length of hydrophobic alkyl chains, resulting in better shear and temperature resistances. The total reduced viscosity was 124.42 mPa·s for cw101, 69.81 mPa·s for cw6-1, 55.38 mPa·s for cw8-0.25, 48.95 mPa·s for cw12-0.25 and 28 mPa·s for cw16-0.25 when the temperature increased from 30 °C to 90 °C. The cw8-2.0 that contains a 2 mol% hydrophobe monomer has the lowest value at 19.12 mPa·s due to the best association. Based on the excellent stability, solubility and rheological properties, we believe that these HAPAM w/w emulsions could find widespread applications.

Preparation and evaluation of hydrophobically associating polyacrylamide coated silica composite as high performance liquid chromatographic stationary phase

A hydrophobically associating polyacrylamide (HAPM)-coated silica packing (HAPM@silica) as a novel stationary phase was synthesized by a simple thermal immobilization to separate multiple polar compounds for the first time. The successful immobilization of HAPM on the silica support was confirmed by elemental analysis, scanning electron microscopy (SEM) and the Brunauer–Emmett–Teller (BET). The thickness of HAPM coating is crucial and the one-layer HAPM@silica stationary phase was demonstrated the highest separation efficiency. Compared with the bare silica and amino modified silica, the new stationary phase showed better separation performance for multiple polar compounds such as bases, alkaloids, carbohydrates and amino acid compounds under the experimental conditions. The chromatographic behaviors were evaluated by investigating the effects of acetonitrile content, water content, mobile phase pH on separation. A typical hydrophilic interaction liquid chromatography (HILIC) retention feature of HAPM based column was observed at the low percentage of water content. The packing material also showed excellent chromatographic repeatability with intraday RSDs of the retention time of five bases less than 0.46% (n = 10) and interday RSDs less than 1.45% (n = 5). In summary, the new chromatographic material can be used for a feasible option for analysis of polar compounds.

Oil recovery performance of a modified HAPAM with lower hydrophobicity, higher molecular weight: A comparative study with conventional HAPAM, HPAM

Adaptability in improving hydrophobically associating polyacrylamide (HAPAM) flooding by reducing hydrophobicity (to decrease retention) while increasing molecular weight (to ensure viscosity), was researched by the comparative study of an accordingly modified HAPAM (M-HAPAM), a conventional HAPAM (C-HAPAM) and a classical hydrolyzed polyacrylamide (HPAM). Attention is paid to their thickening ability, injectivity and propagation, retention, and finally oil-displacing performance. Results show that hydrophobicity reduction helps retention decrement and propagation enhancement of M-HAPAM, making it outperform C-HAPAM with regard to injectivity, propagation, and oil recovery: however, HPAM works best at permeabilities of ∼1μm2∼3μm2, and M-HAPAM needs more hydrophobicity reduction.

Conformation and adsorption behavior of associative polymer for enhanced oil recovery using single molecule force spectroscopy

Hydrophobically associating polyacrylamide (HAPAM) is considered as a promising candidate as a mobility control agent in enhanced oil recovery because of its excellent thickening ability and adsorption capacity. Previous studies have shown that the adsorption capability of HAPAM is higher than that of traditional polyacrylamide, but the reasons are still unclear. In order to uncover why HAPAM can establish a higher resistance factor, the conformations and adsorption behavior of HAPAM on the silica surface were studied by single molecule force spectroscopy (SMFS). For comparison, the partially hydrolytic polyacrylamide (HPAM) was also studied by SMFS under identical conditions. Two types of force profiles with plateau were obtained; indicating that train-like structure was predominant when HPAM was adsorbed on the substrate. For HAPAM, besides the above two types of force profiles, three types of representative force profiles demonstrating single-molecule characteristics were observed. The SMFS results show a strong attachment of the hydrophobic microblock to the silica surface with an adhesion force of 200-280pN in contrast to a weaker adhesion force of only 79.5 pN for HPAM chains on the silica surface. The adhesion force of HAPAM is higher than that of HPAM, so the desorption of HAPAM from silica surface is more difficult than HAPM, leading to the higher retention capacity of HAPAM than that of HPAM.

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

ABSTRACTOrganic/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.

Adaptability of a hydrophobically associating polyacrylamide/mixed‐surfactant combination flooding system to the Shengli Chengdao oilfield

ABSTRACTWe investigated the performance of a combination flooding system composed of hydrophobically associating polyacrylamide (HAPAM) and a mixed surfactant [fatty acid disulfonate anionic gemini surfactant (DMES) plus the nonionic surfactant Triton X‐100 (TX‐100)] under the reservoir conditions of the Shengli Chengdao oilfield. With 1800 mg/L HAPAM and 300–3000 mg/L mixed surfactant, the surfactant–polymer (SP) flooding system reached an ultralow oil–water interfacial tension, and the viscosity of the system was greater than 40 mPa s. After the solution was aged for 120 days, its viscosity was still more than 40 mPa s; this indicated a good aging stability. The core flooding experiments with different porous media permeabilities showed that the SP flooding system created a higher resistance factor and residual resistance factor. In addition, the indoor flooding experiments indicated that the SP combination flooding system increased the enhanced oil recovery by more than 30% over that of the original oil in place compared with the water flooding system. Therefore, it was feasible to use an SP flooding system in the Chengdao oilfield. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40390.

Interaction between Aqueous Solutions of Hydrophobically Associating Polyacrylamide and Dodecyl Dimethyl Betaine

The interaction between hydrophobically associating polyacrylamide (HAPAM) and dodecyl dimethyl betaine (BS-12) is studied through surface tension, interfacial tension (IFT), apparent viscosity, aggregation behavior, and microscopic morphologies. Results show that surface and interface properties of BS-12 are largely affected by HAPAM. BS-12 critical micelle concentrations are increased with the increment of polymer concentrations. Abilities of reduced air-water surface tension and oil-water interfacial tension are dropped. The oil-water interfacial tension to reach minimum time is increased. HAPAM can form network structures in the aqueous solution. Mixed micelles are formed by the interaction between BS-12 micelles and hydrophobic groups of HAPAM in aqueous solution and self-assembly behavior of HAPAM is affected. With the increment of surfactant concentrations, the apparent viscosity, apparent weight average molecular weights (Mw, a), root mean square radius of gyration (〈Rg〉), and hydrodynamic radius of HAPAM increase first and then decline. Moreover, microscopic morphologies of the mixed system are formed from relatively loose network structures to dense network structures and then become looser network structures and the part of network structures fracture.

Effective Viscosity in Porous Media and Applicable Limitations for Polymer Flooding of an Associative Polymer

Hydrophobically associating polyacrylamide (HAPAM) is considered to be a promising candidate for polymer flooding because of its excellent apparent viscosifying capability. Compared with partially hydrolyzed polyacrylamide (HPAM), the resistance factor and residual resistance factor caused by HAPAM tend to be higher. However, the effective viscosity of HAPAM is lower than that of conventional polymer at a concentration of 2 000 mg/L. The dynamic retention capacity of HAPAM is about 2.3 times that of HPAM. The oil displacement efficiency of HAPAM is lower than that of conventional polymer at a concentration of 2 000 mg/L in the homogeneous sandpack model. The oil displacement efficiency of HAPAM is higher than that of HPAM only in the heterogeneous model (permeability ratio 2.8). Neither high nor low permeability ratios are good for the oil displacement efficiency of HAPAM.

The solution behavior of hydrophobically associating zwitterionic polymer in salt water

ABSTRACTThe acrylamide‐based hydrophobically associating zwitterionic polymer was prepared, which was composed of dimethyl‐dodecyl‐allyl ammonium chloride as hydrophobic group and carboxyl betaine 2‐(4‐acrylamido‐propyl‐dimethyl ammonic)‐sodium acetate as functional group. Hydrophobically associating polyacrylamide (HAPAM) was also prepared for comparative study. The behaviors of polymers in pure water and salt solutions were investigated by the means of apparent viscosity test, laser light scattering, atomic force microscope, and fluorescence experiments. The viscosities of polymer solution increased with the increasing of salt concentration, which indicated that the addition of salt resulted in significant antipolyelectrolyte effect in the zwitterionic polymer solution. The results of dynamic laser light scattering experiment also showed that the average hydrodynamic diameters of the zwitterionic polymer molecules increased with the increasing of salt concentration. The network structures had been observed by atomic force microscope and the addition of salt strengthened the formation of network structures. The results of fluorescence experiment showed that the addition of salt could enhance the association of hyrophobically zwitterionic polymer. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39707.

Displacement Characters of Combination Flooding Systems consisting of Gemini-Nonionic Mixed Surfactant and Hydrophobically Associating Polyacrylamide for Bohai OffshoreOilfield

In this paper, the injectivity and displacement characters of a new polymer–surfactant (SP) flooding system consisting of gemini–nonionic mixed surfactant and hydrophobically associating polyacrylamide (HAPAM) have been studied under Bohai offshore oilfield reservoir conditions. The injectivity tests have shown that the SP system could build higher resistance factor (RF) and residual resistance factor (RRF) to expand sweep efficiency in nonheterogeneous reservoirs. A total of 10 core flooding tests were carried out to investigate the effect of heterogeneity, slug composition, and polymer molecular structure. The results have shown that the system could obtain higher recovery owing to higher viscosity and ultralow interfacial tension (IFT) compare to water flooding and polymer flooding. The slug composition, with 0.175% polymer and 0.3% mixed surfactant, which forms a composite with the ratio of 4:1 gemini surfactant to nonionic surfactant, could allow full play to viscosity and IFT economically. Moreover, we found that the SP system with HAPAM could obtain a higher oil recovery by 6–13% original oil in place (OOIP) than a nonmodified one, as a result of viscoelastic rheology. The laboratory core tests provided credible proofs for large scale application with this SP system in Bohai offshore oilfield.

The effect of microstructure on performance of associative polymer: In solution and porous media

Hydrophobically associating polyacrylamide (HAPAM) is considered as a promising candidate of polymer flooding because of its excellent apparent viscosifying capability. However, the effective viscosity and the oil displacement efficiency of HAPAM are lower than those of conventional polymers at a concentration of 2000mg/l. Therefore, the microstructures of two types of polymers were investigated by scanning electron microscopy (SEM) to reveal the relationship between the morphology and properties. The specimens were prepared by accelerated freeze-drying in order to keep polymers with their original morphology without distortion. In aqueous solution, associative polymer exhibited a compact three-dimensional network structure, while only loose network structure was found in conventional polymer. A number of filaments are attached to the associative polymer skeletons when the polymer concentration is higher than the critical association concentration (CAC). But in the porous media, most of the networks of conventional polymer were larger and more integrated than those of associative polymer. It may be interpreted by absorption loss of HAPAM and spatial confinement in porous medium.

Solution Property Investigation of Combination Flooding Systems Consisting of Gemini–Non-ionic Mixed Surfactant and Hydrophobically Associating Polyacrylamide for Enhanced Oil Recovery

The aim of this work was to investigate the solution properties of a new polymer–surfactant (SP) flooding system, including hydrophobically associating polyacrylamide (HAPAM) and mixed surfactant [mixture of fatty acid disulfonate anionic gemini surfactant (DMES) and non-ionic surfactant Triton X-100 (TX-100)]. The critical micelle concentrations (cmc’s) of four gemini surfactants were smaller than 100 mg L–1. Furthermore, their interfacial tensions (IFTs) could reach an ultralow value with Bohai oil at lower concentrations. Through optimized formulation, we found that DMES-14 had better properties and was selected as the major component of the surfactant. We designed an optimal formulation of the SP system with 1750 mg L–1 HAPAM and 3000 mg L–1 mixed surfactant (the mass ratios of DMES-14 and TX-100 are from 4:1 to 5:1). The SP system (ratio of 4:1) with a very small surfactant concentration could reach ultralow IFT with different crude oils, which proved that the simpler component surfactant had better reservoir compatibility. TX-100 could widen the “window” of increasing viscosity and weaken the disadvantage of the interaction between HAPAM and the surfactant. The stability of this SP system was evaluated by the temperature, mineralized degree, shearing, aging time, adsorption, and chromatographic separation. All of experiments showed that it still keeps higher viscosity and ultralow IFT with different evaluation conditions; therefore, it is feasible to use as a SP combination flooding system for enhanced oil recovery (EOR).

Self-Assembly of Hydrophobically Associating Polyacrylamide and Gemini Surfactant

The self-assembly of hydrophobically associating polyacrylamide(HAPAM) and the effect of adding gemini surfactant(dimyristic acid glycol ester di(α-sodium sulfonate),DMES-14) were studied by static light scattering,dynamic light scattering,and fluorometry.HAPAM formed hydrophobic microdomains in solution through self-assembly,which decreased the fluorescence intensity ratio(I1/I3) of the first peak(373 nm) and the third peak(383 nm) in the emission spectrum of pyrene as the polymer HAPAM concentration(C P) was increased until a plateau was reached at high C P.When surfactant was added to the polymer solution,the interaction between HAPAM and surfactant resulted in the formation of mixed micelles.This caused I1 /I3 to decrease as the surfactant concentration(C S) was increased at the same polymer concentration until C S was greater than 30 mg · L-1,after which point I1 /I3 showed little change.The aggregation number of aggregates in the mixed system containing surfactant and polymer decreased at first and then increased as C P was increased.A certain amount of surfactant could enhance interchain interactions,while excess surfactant broke down interchain interactions between the hydrophobic groups of HAPAM,which resulted in maximum values of the apparent weight average molecular weight(M w,a),root-mean-square radius of gyration(R g ),and hydrodynamic radius(R h ) of HAPAM as C S was increased.Rg/Rh increased slowly as C S was increased,which reflected the relative stretch of the polymer chains.

Self-Assembly Behavior of Hydrophobically Associating Polyacrylamide in Salt Solution

The self-assembly behavior of hydrophobically associating polyacrylamide(HAPAM)in salt solution was studied by static light scattering,dynamic light scattering,and atomic force microscopy(AFM). The apparent weight average molecular weight(Mw,a ),root mean square radius of gyration(Rg), hydrodynamic radius(Rh),and the second virial coefficient(A2),were investigated.The ratio ofRg toR h was used to determine the molecular shape of the polymer in salt solution.As the salt concentration increased,the polymer chain transformed from stretch to curl.

Studies on the self‐assembly behavior of the hydrophobically associating polyacrylamide

AbstractContrasted with partially hydrolyzed polyacrylamide (HPAM), the self‐assembly behavior and microstructure of hydrophobically associating polyacrylamide (HAPAM) in aqueous solution have been studied by means of fluorescence spectrum, transmission electron microscopy (TEM), atomic force microscope (AFM), and apparent viscosity test in this article. The fluorescent probe analysis indicates that the HAPAM molecules will form associating aggregates in pure water. The results show that HAPAM can easily self‐assemble to form an aggregate by hydrophobic driving force in dilute aqueous solution. The association of hydrophobic groups of the HAPAM causes the formation of supermolecule, so there are associating aggregates formed at very low concentration and then leads to the formation of network at a higher concentration. TEM and AFM measurements show that a distinct network structure has been formed in 1000 mg L−1 of HAPAM solution, indicating the strong association of hydrophobic groups. These results are consistent with the viscosity measurement and reveal that the excellent viscosification of HAPAM is due to the association of hydrophobic groups in the aqueous solution. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Interaction of Hydrophobically Associating Polyacrylamide with Gemini Surfactant

A fatty acid disulfonate anionic gemini surfactant was prepared and the structure of the surfactant was characterized by 1 H-NMR.Hydrophobically associating polyacrylamide was prepared according to a procedure from literature.The interaction between the hydrophobically associating polyacrylamide (HAPAM) and the anionic gemini surfactant was studied by surface/interfacial tension,apparent viscosity,and atomic force microscopy (AFM).Experimental results show that HAPAM can form a network structure in the aqueous solution by self assembly.Mixed micelles are formed by the interaction of gemini surfactant micelles and the hydrophobic microdomain of the hydrophobically associating polyacrylamide in aqueous solution,which plays a remarkable role in the surfactant and polymer assembly.Mixed micelles can enhance the inter-or intra-molecular association between the polymer molecules and the surfactant,which increases the strength of the network formed by the hydrophobically associating polyacrylamide.The apparent viscosity of the solution increased by the addition of the gemini surfactant.When the addition of the gemini surfactant exceeded a certain amount,the association between the hydrophobic groups of the polymer decreased and the network formed by hydrophobically associating interaction was weakened by the surfactant micelles,which led to a decrease in solution viscosity.The polymer also largely influenced the interfacial properties of the gemini surfactant,especially the dynamical interfacial tension.A high polymer concentration led to an increase in the time required to reach equilibrium.

Retention Behaviors of Hydrophobically Associating Polyacrylamide Prepared via Inverse Microemulsion Polymerization Through Porous Media

The retention behavior of hydrophobically associative polyacrylamide (HAPAM) with homogeneous composition in porous media was investigated. The results showed that HAPAM could exhibit different retention behavior, compared to PAM due to the existence of hydrophobic association group in HAPAM molecular frame. The critical association concentration could also be reflected by the curves between HAPAM concentration and retention amount. The retention amount of HAPAM was higher than that of polyacrylamide (PAM) and was smaller than the absorption amount of HAPAM. The retention mechanism was mainly controlled by adsorption mechanism.

Solution Association Characterization of Hydrophobically Associating Polyacrylamide Obtained from Produced Fluids

The hydrophobically associating polyacrylamide (HAPAM) obtained from produced fluids with compositional homogeneity was systematically investigated by zero-shear viscosity, fluorescence, sand-pipes experiment and adsorption behavior. The results showed that HAPAM obtained from produced solution through porous media has been possession in hydrophobic association character. The critical association concentration (CAC) determined by viscosity method, fluorescence spectroscopy method and micro-pore method have no obvious change compared with the original polymer. The hydrophobic associative capability of HAPAM obtained from produced fluids was smaller than that of original HAPAM. Compared to original PAM and PAM obtained from produced fluids, HAPAM obtained from produced fluids still exhibits promising applied potential. It reveals the possibility that HAPAM obtained from produced could be re-used for enhance oil recovery.

Dissolution Characteristics of Hydrophobically Associating Polyacrylamide in Stirred Tanks

Enhanced oil recovery (EOR) by means of polymer flooding is an important technology for the strategic development of offshore oilfields in China. Hydrophobically associating polyacrylamide (HAPAM) has been recently proposed as a new flooding agent. The solubility of HAPAM is low, which is the bottleneck for further improving the oil recovery through polymer flooding in offshore oilfield. Stirred tanks have been used on offshore platforms to enhance HAPAM dissolving. But there is little literature on the study of HAPAM dissolving characteristics in stirred tanks. In this paper, effects of temperature, salinity, stirring speed, impeller type and stirring method on the dissolution of HAPAM are reported. The experimental results manifest that the dissolving rate of HAPAM increases with temperature and stirring speed, but the viscosity of the polymer solution decreases. There is an optimal range of salinity for polymer dissolving. Combining the operation mode of up-pumping with varying stirring speed, hydrofoil impeller can accelerate the dissolution of HAPAM and maintain a high solution viscosity.

Solution and Adsorption Properties of Hydrophobically Associating Polyacrylamide Prepared in Inverse Microemulsion Polymerization

The hydrophobically associative polyacrylamide (HAPAM) with homogeneous composition was prepared in inverse microemulsion polymerization. The homogeneity was proved by polymerization kinetic. The critical association concentration (CAC) was measure by three methods: viscosity method, fluorescence method and micro-pore method. The results showed that the HAPAM still could exhibit hydrophobic association interaction in porous media under flowing condition. HAPAM could present adsorption of multi-layer due to the hydrophobic association interaction. It's the hydrophobic association interaction that made the adsorption behavior differ from neutral PAM.