Preparation and Solution Characteristics of a Novel Hydrophobically Associating Terpolymer for Enhanced Oil Recovery

Hydrophobically associating terpolymers were prepared by the micellar copolymerization technique using acrylamide (AM), 2-trimethylammonium ethyl methacrylate chloride (TMAEMC) as a cationic monomer, and small amounts of 5,5,5-triphenyl-1-pentene (TP<0.5 mol-%) as the hydrophobe. The structure of the copolymer was characterized by FT-IR and ¹H-NMR. The aqueous solution properties of the terpolymers were also investigated as functions of polymer concentration, salinity, temperature and shear rate. The results showed that the thickening behavior of these terpolymers are remarkably dependent on both the number and length of hydrophobic segments in the copolymer chains. As expected, the terpolymers exhibited improved viscosity enhancement properties as the concentration exceeded 0.25 g⋅dL⁻¹, due to intermolecular hydrophobic association. Additional evidence for hydrophobic microdomains was obtained utilizing pyrene-probe fluorescence. Additionally, the ternary copolymers showed favorable salt tolerance, temperature resistance, and recoverable viscosity after shearing.     

Characterization, Solution Behavior, and Microstructure of a Hydrophobically Associating Nonionic Copolymer

To obtain an oil-displacement polymer with good thermal stability and solution properties, self-assembling acrylamide (AM)/4-butylstyrene (BST) copolymers (PSA) were synthesized by the micellar copolymerization technique. The resulting polymer was characterized by elemental analysis and UV and FT-IR spectroscopy. Conventional DSC measurement was used successfully to characterize the hydrophobic microblock structure of PSA, and two glass transition temperatures were found in the polymer: at 203 °C for the AM segments and at 106 °C for the hydrophobic BST segments. The initial decomposition temperature (234 °C) of the polymer is higher than that of polyacrylamide (210 °C). The DSC and TG results suggest that incorporation of BST into PSA enhances the molecular rigidity and thermal stability of the polymer. The apparent viscosity of a PSA solution greatly depends on the amount of BST in the polymer, and the polymer exhibits salt-thickening, temperature-thickening, thixotropy, pseudo-plastic behavior, anti shearing, and good anti-aging properties at 80 °C. In addition, the apparent viscosities of PSA solutions are increased remarkably by the addition of a small amount of surfactant. AFM measurements show that large block-like aggregates and small compact aggregates are formed in aqueous solutions of 0.4 g⋅dL⁻¹ PSA because of strong intermolecular hydrophobic associations, despite the low molecular weight, and their sizes increase upon addition of a small amount of salt.     

疏水缔合(丙烯酰胺十六烷基二甲基烯丙基氯化铵-2-丙烯酰胺基-2-甲基丙磺酸)三元共聚物的合成与性能研究

疏水缔合水溶性聚合物是指在聚合物亲水性大分子链上引入少量疏水基团的一类水溶性聚合物[1～5].在水溶液中,疏水基团之间由于憎水作用而发生聚集,使大分子链产生分子内与分子之间缔合.在临界缔合浓度以上,以分子间缔合为主,增大了流体力学体积,因此,具有较好的增粘作用.疏水基的加入可大幅度地改变聚合物的流变性能.在聚合物驱油中的流度控制,提高波及效率、以及调剖中起到非常重要的作用.     

Solution properties of thermothickening copolymers bearing hydrocarbon end‐capped oxyethylene units

Novel thermothickening copolymers composed of acrylamide and a macromer bearing hydrocarbon end‐capped oxyethylene units were synthesized. Influences of polymer concentration, salt content, shear rate, and temperature on the solution behavior were investigated. The polymer solution exhibited shear‐thickening behavior at low‐to‐moderate shear rates (<50 s^?1), and the shear‐thickening behavior was dependent on polymer concentration, NaCl content, and temperature. With the increase of salinity, apparent viscosity of polymer solution increased dramatically (especially at low shear rates). At higher NaCl content (>20 wt %), polymer solutions became physical gel, and the apparent viscosity increased by several orders of magnitude. The polymer solutions exhibited excellent thermothickening behavior, even at the low concentration of 0.15 wt %. The results of rheological measurements showed that the storage and loss modulus were successfully fitted to a single Maxwell element at low temperature (<60 °C). © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1799–1808, 2010     

Stimuli‐responsive ampholytic terpolymers of N‐acryloyl‐valine,acrylamide, and (3‐acrylamidopropyl)trimethylammonium chloride: Synthesis,characterization, and solution properties

Low‐charge density ampholytic terpolymers composed of acrylamide (AM), (3‐acrylamidopropyl)trimethyl ammonium chloride (APTAC), and N‐acryloyl‐valine were prepared via free‐radical polymerization in 0.5 M NaCl to yield terpolymers with random charge distributions. Sodium formate (NaOOCH) was employed as a chain transfer agent during the polymerization to suppress gel effects and broadening of the molecular weight distribution (MWD). Terpolymer compositions were determined by ¹³C NMR spectroscopy. Terpolymer molecular weights (MWs) and polydispersity indices (PDIs) were obtained via size exclusion chromatography/multi‐angle laser light scattering (SEC‐MALLS). Intrinsic viscosity values determined from SEC‐MALLS data using the Flory–Fox relationship were compared with those determined by low‐shear dilute solution viscometry and found to be in good agreement. SEC‐MALLS experiments allowed examination of radius of gyration‐MW (R_g‐M) relationships and the Mark‐Houwink‐Sakurada intrinsic viscosity‐MW ([η]‐M) relationships for terpolymers. The R_g‐M and [η]‐M relationships indicated little or no excluded volume effects under SEC conditions indicating that the terpolymers were in near theta conditions in an aqueous buffer solution. Potentiometric titration experiments were performed in deionized (DI) water. These studies revealed that the apparent pK_a of the AMVALTAC terpolymers increases with increasing VAL content. The solution properties of low‐charge density ampholytic terpolymers have been studied as functions of solution pH, ionic strength, and polymer concentration. The charge‐balanced terpolymers exhibit polyampholyte behavior at pH values ≥ 6.5. As solution pH is decreased, these charge‐balanced terpolymers become increasingly cationic due to the protonation of the VAL repeat units. Charge‐imbalanced terpolymers generally exhibit polyelectrolyte behavior, although the effects of intramolecular electrostatic interactions (e.g., polyampholyte effects) on the hydrodynamic volume are evident at certain values of solution pH and salt concentration. The solution behavior of the terpolymers in the dilute regime correlates well with that predicted by various polyampholyte solution theories. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3125–3139, 2006     

孪尾疏水缔合水溶性共聚物聚(丙烯酰胺/丙烯酸钠/N,N-二己基丙烯酰胺)/十二烷基硫酸钠水溶液的粘度行为

水溶性三元共聚物;孪尾疏水缔合水溶性共聚物聚(丙烯酰胺/丙烯酸钠/N;N-二己基丙烯酰胺)/十二烷基硫酸钠水溶液的粘度行为     

孪尾疏水缔合三元共聚物的粘度行为:水解度的影响

以十二烷基硫酸钠(SDS)为表面活性剂,利用氧化还原体系、采用前加碱共聚-共水解的方法制备了孪尾疏水缔合水溶性三元共聚物聚(丙烯酰胺／丙烯酸钠／N,N-二己基丙烯酰胺)[P(AM/NaAA／DiC6AM)],研究了P(AM／NaAA／DiC6AM)稀溶液及亚浓溶液的性能。随理论水解度的增加,P(AM／NaAA／DiC6AM)水溶液的特性粘数[η]增加,Huggins常数KH减小。P(AM／NaAA／DiC6AM)水溶液的表现粘度随理论水解度的增加而增加,随温度、剪切速率的增加而降低,随剪切速率的增加开始时降低较快而后变化较小。P(AM／NaAA/DiC6AM)在盐溶液中随NaCl、CaCl2质量浓度的增加,出现盐增粘现象;理论水解度不同的P(AM／NaAA／DiC6AM)与SDS水溶液的表现粘度在wSDS=0．050～0．400g／L范围内随SDS质量浓度的变化差别不大。     

pH‐responsive ampholytic terpolymers of acrylamide,sodium 3‐acrylamido‐3‐methylbutanoate,and (3‐acrylamidopropyl)trimethylammonium chloride. II. Solution properties

The solution properties of low‐charge‐density ampholytic terpolymers of acrylamide, sodium 3‐acrylamido‐3‐methylbutanoate, and (3‐acrylamidopropyl)trimethylammonium chloride were studied as functions of the solution pH, ionic strength, and polymer concentration. Terpolymers with low charge densities, large charge asymmetries, or both exhibited excellent solubility in deionized (DI) water, and higher charge density terpolymers were readily dispersible in DI water; however, the higher charge density terpolymer solutions separated into polymer‐rich and polymer‐poor phases upon standing over time. Charge‐balanced terpolymers exhibited antipolyelectrolyte behavior at pH values greater than or equal to the ambient pH (6.5 ± 0.2); the same terpolymers behaved increasingly as cationic polyelectrolytes with decreasing solution pH because of the protonation of the 3‐acrylamido‐3‐methylbutanoate (AMB) repeat units. Unbalanced terpolymers generally exhibited polyelectrolyte behavior, although the effects of intramolecular electrostatic attractions (i.e., polyampholyte effects) on the hydrodynamic volume of the unbalanced terpolymer coils were evident at certain values of the solution pH and salt concentration. The dilute‐solution behavior of the terpolymers correlated well with the behavior predicted by several polyampholyte solution theories. In the semidilute regime, solution viscosities increased with increasing terpolymer charge density, and this indicated a significant enhancement of the solution viscosity by intermolecular electrostatic associations. Upon the addition of NaCl, semidilute‐solution viscosities tended to decrease because of the disruption of the intermolecular electrostatic associations. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3252–3270, 2004     

Polyampholyte terpolymers of amphoteric,amino acid‐based monomers with acrylamide and (3‐acrylamidopropyl)trimethyl ammonium chloride

Low‐charge‐density amphoteric copolymers and terpolymers composed of acrylamide, (3‐acrylamidopropyl)trimethyl ammonium chloride, and the amino acid derived monomers (e.g., N‐acryloyl valine, N‐acryloyl alanine, and N‐acryloyl aspartate) were prepared via free‐radical polymerization in aqueous media to yield terpolymers with random charge distributions and homogeneous compositions. Sodium formate (NaOOCH) was employed as a chain transfer agent during the polymerization to suppress gel effects and broadening of the molecular weight distribution. Terpolymer compositions were determined by ¹³C and ¹H NMR spectroscopy. Terpolymer molecular weights and polydispersity indices were obtained via size exclusion chromatography/multi‐angle laser light scattering, and hydrodynamic diameter values were obtained via dynamic light scattering. The solution properties of low‐charge‐density amphoteric copolymers and terpolymers have been studied as a function of solution pH, ionic strength, and polymer concentration. The low‐charge‐density terpolymers display excellent solubility in deionized (DI) water with no phase separation. The charge‐balanced terpolymers exhibit antipolyelectrolyte behavior at pH values ≥(6.5 ± 0.2). As solution pH is decreased, these charge‐balanced terpolymers become increasingly cationic because of the protonation of the anionic repeat units. Charge‐imbalanced terpolymers generally demonstrate polyelectrolyte behavior, although the effects of intramolecular electrostatic interactions (e.g., polyampholyte effects) on the hydrodynamic volume are evident at certain values of solution pH and salt concentration. The aqueous solution behavior (i.e., globule‐to‐coil transition at the isoelectric point in the presence of salt and globule elongation with increasing charge asymmetry) of the terpolymers in the dilute regime correlates well with that predicted by the polyampholyte solution theories of Dobrynin and Rubinstein as well as Kantor and Kardar. Examination of comonomer charge density, hydrogen‐bonding ability, and spacer group (e.g., the moiety separating the ionic group from the polymer chain) indicates that conformational restrictions of the amino acid comonomers result in increased chain stiffness and higher solution viscosities in DI water and brine solutions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4479–4493, 2006     

Compositional heterogeneity effects in multisticker associative polyelectrolytes prepared by micellar polymerization

An aqueous micellar radical polymerization technique has been used to prepare water‐soluble polyelectrolytes of acrylamide (AM) and sodium 2‐acrylamido‐2‐methylpropanesulfonate (NaAMPS) hydrophobically modified with low amounts (2–4 mol %) of N,N‐dihexylacrylamide (DiHexAM). This synthesis method leads to multisticker polymers, in which the number and length of the hydrophobic blocks vary with the degree of conversion. Kinetic studies show an appreciable compositional heterogeneity for these polymers, in contrast to their neutral analogues (i.e., AM/DiHexAM copolymers). The drift in composition observed for the AM/NaAMPS/DiHexAM terpolymers is attributed to the electrostatic repulsion between the negatively charged growing polymeric chains, located in the aqueous continuous medium, and the anionic sodium dodecyl sulfate micelles, inside of which the hydrophobic monomer is entrapped. It is shown that an optimization of the polymerization process can be achieved, which gives terpolymers of homogeneous and well‐defined compositions. The thickening ability of the hydrophobically modified polyelectrolytes is directly affected by the extent of their compositional heterogeneity: an increase in the sample homogeneity leads to a significant viscosity enhancement and marked elastic properties of the polymer solutions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3261–3274, 2003     

Rheologic Properties of a Water-Soluble Terpolymer with Vinyl Biphenyl

A water-soluble acrylamide-modified terpolymer (PAAP) with sodium 2-acrylamido-2-methylpropane sulfonate and vinyl biphenyl as the hydrophobic monomer was synthesized to obtain a polymeric thickening agent applied in middle- and low-permeability oil reservoirs. The polymer is expected to possess a low molecular weight and high solution viscosity. The steady-state consecutive shear cycles of PAAP in aqueous and brine solutions were measured, and the viscoelastic properties of PAAP solutions were investigated as a function of polymer, NaCl and sodium dodecylbenzene sulfonate (SDBS) concentrations. The aqueous PAAP solutions exhibits pseudoplastic and thixotropic behavior over the range of shear rate and shear thickening behavior at very low shear rate. The steady-state shear results show that some disrupted associating aggregates at high shear rate can be reformed during the shear reversion process and the suitable shear rate is favorable to the formation of hydrophobically associative structures in the brine solutions. Above 0.05 g⋅dL⁻¹ PAAP, aqueous PAAP solutions have predominantly elastic character over the range of angular frequency that is strengthened with increasing polymer concentration. The PAAP brine solutions exhibit predominantly elastic behavior only above 3 rad⋅s⁻¹ and a salt-thickening effect. By addition of an optimum amount of SDBS (0.5–0.8 mmol⋅L⁻¹), the complex viscosities become much higher than the dynamic viscosities, although the loss tangent values increase owing to the formation of loose associative structures.     

Self-assembly of hydrophobic associating polyacrylamide prepared by aqueous dispersion polymerization

Abstract

Hydrophobic associating polyacrylamide (PDH) was prepared via aqueous dispersion polymerization in the presence of ammonium sulfate. In order to dissolve the polymer at high salt solution concentration, a hydrophobic precursor monomer with two cationic heads was synthesized. Upon polymerization, spherical PDH polymer particles were obtained with an average size of about 9.1?µm. The PDH was fully dispersed in water in twenty seconds, leading to a transparent gel. PDH demonstrated superior properties compared to the partially hydrolyzed polyacrylamide, for instance, regarding salt tolerance and shear resistance. Addition of a small amount of an anionic surfactant significantly affected the PDH dispersion viscosity due to the formation of mixed micelles. The viscosity slightly decreased after strong shearing (>500?s^?1), showing excellent shear resistance. These features indicate that the synthesized PDH offers a great potential for application in hydraulic fracturing and enhanced oil recovery.     

Rheological behavior of an acrylamide-based terpolymer with p-vinylbenzyl-terminated octylphenoxy poly(ethylene oxide)

A comb-like associating terpolymer PAOE was synthesized from acrylamide (AM), sodium 2-aciylamido-2-methylpropane sulphonate (NaAMPS) and a novel macromonomer: p-vinylbenzyl-terminated octylphenoxy poly(ethylene oxide) (VOE, degree of polymerization: 4??using aqueous free-radical copolymerization technique. The polymer chains were still comparatively extended in the brine solutions at low polymer concentrations. This leaded to the formation of continuous network structures via the intermolecular hydrophobic associations of the octylphenyl groups in despite of the addition of NaCl. As a result, PAOE predominantly exhibited significant elastic characters in brine solutions at 0.5?C9 g/dL NaCl, as well as in aqueous solutions. The viscous and elastic character decreased slightly with increasing temperature from 25 to 45°C for the PAOE brine solution with 0.5 g/dL NaCl. The PAOE aqueous and brine solutions displayed obvious shear thickening behavior upon consecutive steady shear cycles. The brine solution also showed the excellent thickening properties, salt-thickening behaviors twice, and resistance to salt.     

丙烯酰胺-苯乙烯双亲嵌段共聚物水溶液的粘度性能

通过改变丙烯酰胺 (AM)与苯乙烯 (St)两单体的投料比 ,在微乳液介质中制备了分子组成系列变化的丙烯酰胺 苯乙烯双亲嵌段共聚物 (PAM b PSt) ,使用旋转粘度计测定了共聚物水溶液的表观粘度 ,详细考察了共聚物浓度、共聚物链结构、剪切速率、盐度及温度等因素对共聚物水溶液表观粘度的影响规律 .研究结果表明 ,由于PAM b PSt分子链中的PSt疏水嵌段链段之间具有强的疏水缔合作用 ,导致其具有独特的流变性能 .当共聚物水溶液的浓度高于某一临界值后 ,疏水缔合作用以分子间的缔合为主 ,大分子链之间会形成动态物理交联网络 ,增大了流体力学体积 ,使PAM b PSt水溶液可产生良好的增稠性能 ;疏水缔合作用是一吸热过程 ,升高温度有利于分子间的缔合 ,因此PAM b PSt水溶液具有良好的耐温性 ;聚合物水溶液中盐类物质的存在 ,会增强溶剂的极性 ,有利于分子间的缔合 ,使PAM b PSt水溶液具有良好的耐盐性 .     

Thickening and Associating Behavior in Aqueous Solutions of a Terpolymer with Poly(ethylene oxide) Side Chains

A water-soluble terpolymer (PAVA) was synthesized by aqueous free radical copolymerization technique using acrylamide(AM), sodium 2-acrylamido-2-methylpropane-sulphonate (NaAMPS) and a macromonomer: p-vinylbenzyl-terminated octylphenoxy poly(ethylene oxide) (VPEO, degree of polymerization: 10). The remarkable intermolecular hydrophobic associations were formed in water and a brine solution for this polymer, which resulted in a good thickening effect, resistance to salt and salt-thickening. The hydrophobically associating microstructures of PAVA in aqueous solutions were measured by the fluorescent probe and scanning electron microscope. As polymer concentration was increased in water and brine solutions, the associating strength and non-polarity of hydrophobic microdomains increased remarkably. However, at the polymer concentrations higher than 0.20 g/dL, the non-polarity of hydrophobic microdomains tended to remain constant, and the I ₁/I ₃ value changed slightly in 0.5 g/dL NaCl. The continuous associating structures were formed by the expanded polymer chains in brine solutions, as well as in water. As the NaCl concentration increased, the non-polarity of associating microstructures increased slowly, but the compact degree of these microstructures increased.     

SEM Morphologies of a Water-Soluble Terpolymer with Vinyl Biphenyl in Aqueous and Brine Solutions

A terpolymer PAAP, synthesized from acrylamide (AM), vinyl biphenyl (VP), and sodium 2-acrylamido-2-methylpropane sulfonate (NaAMPS), exhibits intermolecular hydrophobically associating behavior in water and aqueous brine solutions. A scanning electron microscope (SEM) was used to observe the conformations of polymer chains and morphologies of their associating microstructures in pure water and in brine solutions. This was done to reveal the relevant relationships between solution properties and associated microstructures for the PAAP polymer in pure water and brine solutions, and the mechanisms for the previously reported viscoelastic behavior of PAAP solutions. Continuous supermolecular associating network structures are formed via strong intermolecular hydrophobic association of biphenyl groups in an aqueous 0.1 g⋅dL⁻¹ PAAP solution, which leads to the excellent viscoelastic character of aqueous PAAP solutions. With increasing polymer concentration, the network structures of the polymer become much larger and more compact in aqueous solution, which results in the excellent thickening properties of their solutions. The SEM results reveal that the elongated conformations of molecular chains in aqueous PAAP solutions are favorable for intermolecular hydrophobic association. With the addition of NaCl, the associating network structures of PAAP are destroyed because of electrostatic shielding effects on the –SO₃^-\mathrm{SO}_{3}^{-} groups, and huge tree-like associated structures are formed. This results in a decrease in the solution viscosity and a loss of viscoelastic properties of PAAP solutions. However, with increasing NaCl concentration, the number and size of the aggregates increase, which results in the salt-thickening behavior of PAAP brine solutions.     

Synthesis and solution behavior of comb‐like terpolymers with poly(ethylene oxide) macromonomer

A novel macromonomer: p‐vinylbenzyl‐terminated octylphenoxy poly(ethylene oxide) (polymerization number: 18) (VBPEO) was synthesized. The comb‐like acrylamide‐based terpolymers (PVEA) were synthesized by aqueous free‐radical copolymerization technique using acrylamide (AM), VBPEO and sodium 2‐acrylamido‐2‐methylpropane sulphonate (NaAMPS). The macromonomer and PVEA polymer were characterized with Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance (¹H NMR). The polymers exhibited self‐assembly behavior in water and the brine solutions. The polymers could be employed in the oil reservoirs of either the high or medium to low permeability due to the low intrinsic viscosities. The optimum NaAMPS feed amount could not only increase the water solubility, but also facilitate the intermolecular associations. Implementing VBPEO into the polymer greatly increased the rigidity of molecular chains, resulting in a high apparent viscosity of the PVEA in water and the brine solutions. The PVEA brine solutions exhibited both excellent uni‐ and bi‐valent cation resistance, salt‐ and heat‐thickening twice, pseudoplastic behavior, and thixotropy. The SEM morphologies showed that the expanded polymer bundles as well as the associated structures with huge sizes were formed for PVEA in water and that the continuous network structures were still formed in the PVEA brine solutions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1241–1250, 2010     

Association in Unsalted and Brine Solutions of a Water-Soluble Terpolymer with <Emphasis Type="Italic">p</Emphasis>-Vinylbenzyl-Terminated Octylphenoxy Poly(ethylene oxide)

An associating terpolymer (PAOE) of acrylamide (AM), sodium 2-acrylamido-2-methylpropane sulphonate (NaAMPS), and a novel macromonomer: p-vinylbenzyl-terminated octylphenoxy poly(ethylene oxide) (VOE, degree of polymerization: 4) was synthesized by aqueous free-radical copolymerization. The PAOE polymer exhibited excellent thickening properties in unsalted and brine solutions. The electrostatic shielding of repulsive interactions of the polymer was much weaker than that of the linear associating polymers with small hydrophobic monomers. This brine solution exhibited unexpected salt-thickening behaviors twice, and good resistance to salt and ageing. The intermolecular hydrophobic association in unsalted and brine PAOE solutions, as functions of polymer and NaCl concentration, were characterized by fluorescence spectroscopy. With the addition of NaCl, the polymer chains were comparatively extended and continuous network structures were formed via the intermolecular hydrophobic association in brine solutions as well as in unsalted solutions at 0.15–0.25 g⋅dL⁻¹ PAOE, as observed by a scanning electron microscope (SEM).     

Synthesis and aqueous solution properties of hydrophobically modified anionic acrylamide copolymers

In this investigation, hydrophobically modified polyacrylamide with low amounts of anionic long‐chain alkyl was synthesized by the free radical polymerization in deionized water. This water‐soluble copolymerization method is more convenient compared with the traditional micellar copolymerization methods. The copolymers were characterized using Fourier transform infrared, ¹H NMR, and the molecular weight and polydispersity were determined using gel permeation chromatography. The solution behavior of the copolymers was studied as a function of composition, pH, and added electrolytes. As NaCl was added to solutions of AM/C₁₁AM copolymers or pH was lowered, the shielding or elimination of electrostatic repulsions between carboxylate groups of the C₁₁AM unit lead to coil shrinkage. The steady shear viscosity and dynamic shear viscoelastic properties in semidilute, salt‐free aqueous solutions were conducted to examine the concentration effects on copolymers. In addition, the shear superimposed oscillation technique was used to probe the structural changes of the network under various stresses or shear conditions. We prepared hydrophobically modified polyacrylamide with N‐alkyl groups in the aqueous medium. The advantage of this method is that the production is pure without surfactants. These results suggest that the unique aqueous solution behavior of the copolymers is different from conventional hydrophobically associating acrylamide. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2465–2474, 2008     

新型疏水缔合聚合物P(AM/POEA)与表面活性剂的相互作用

采用粘度法、荧光探针和透射电镜研究了新型疏水缔合聚合物P(AM/POEA)和表面活性剂SDS和CTAB在水溶液中的相互作用. 聚合物P(AM/POEA)结构中, 疏水体(2-苯氧乙基丙烯酸酯)呈嵌段状无序地分布在聚丙烯酰胺主链上. 这类聚合物很容易和表面活性剂相互作用, 通过疏水缔合, 形成混合胶束状聚集体, 导致溶液粘度剧增. 随聚合物溶液中SDS的加入, 溶液粘度发生大幅度起伏变化, 出现最大值. 粘度最大值对应的表面活性剂浓度c_S,max位于表面活性剂CMC附近, 并发现它的位置不随聚合物微结构而变化. 然而它们缔合作用的增粘程度却与聚合物疏水体含量X_H及疏水嵌段尺寸N_H有关. 在实验浓度范围内, X_H和N_H愈大, 溶液的粘度越高. 此外用透射电镜直接观察到聚合物/表面活性剂体系中聚集体的交联结构形貌.