Synthesis,characterization, rheological behavior,and shear response of hydrophobically modified polyacrylamide and network structure of its microhydrogel

Octylphenol polyoxyethylene acrylate (OP‐10‐AC) was synthesized, and then OP‐10‐AC was copolymerized with acrylamide (AM) to form hydrophobically modified polyacrylamide P(AM/OP‐10‐AC) through micellar copolymerization. OP‐10‐AC content and rheology behavior of P(AM/OP‐10‐AC) were investigated in detail. Especially, under the conditions of different test methods, P(AM/OP‐10‐AC) showed interesting shear responsive behavior. The results of rheology study show that OP‐10‐AC content, polymer solution concentration, salt solution concentration, and different test methods powerfully influenced shear viscosity of aqueous solutions of P(AM/OP‐10‐AC). In addition, according to the dynamic shear experimental results, the critical hydrogel concentration range (CHCR) could be confirmed for aqueous solutions of P(AM/OP‐10‐AC). Above CHCR, these polymer solutions were essentially a kind of microhydrogels, which could explain the effect of concentration and hydrophobe content on their shear viscosity and viscoelasticity from the microstructure's point of view. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of fluorocarbon‐modified poly(N‐isopropylacrylamide)

Poly(N‐isopropylacrylamide) copolymers (PNIPAMs) containing pendent perfluoroalkyl (R_F) or dodecyl groups have been synthesized by copolymerization of NIPAM with small amounts of R_R‐acrylates or ‐methacrylates containing a sulfonamido moiety between the acrylate and R_F groups or with dodecyl acrylate. Evidence for strong intermolecular hydrophobic association of the fluorocarbon groups is provided by large viscosity increases with copolymer concentration and upon addition of NaCl and surfactants. These interactions appear to be much stronger than that of the corresponding copolymers of poly(N,N‐dimethylacrylamide) with similar comonomer contents. Hydrophobic association between the R_F groups is found to be much stronger than that of the corresponding dodecyl groups. The viscosity of some of the copolymer solutions, particularly in the presence of perfluorocarbon surfactants, was unusually temperature sensitive, decreasing by a factor of at least 1000 upon increasing the temperature from 10 to 20 °C. This large decrease is most probably related to the collapse of the copolymer coils near the lower critical solution temperature. This is in sharp contrast to the corresponding polyacrylamide or poly(N,N‐dimethylacrylamide) R_F‐acrylate copolymers that show viscosity increases with increasing temperature in the 40–60 °C range. The NIPIAM copolymers were also found to be different from the acrylamide or N,N‐dimethylacrylamide perfluorocarbon acrylate copolymers in that they were found to be Newtonian at a low R_F content but dilatant at a higher comonomer content. © 2000 Society of Chemical Industry     

Viscosity behavior and surface and interfacial activities of hydrophobically modified water‐soluble acrylamide/N‐phenyl acrylamide block copolymers

In this study, the viscosity behavior and surface and interfacial activities of associative water‐soluble polymers, which were prepared by an aqueous micellar copolymerization technique from acrylamide and small amounts of N‐phenyl acrylamide (1.5 and 5 mol %), were investigated under various conditions, including the polymer concentration, shear rate, temperature, and salinity. The copolymer solutions exhibited increased viscosity due to intermolecular hydrophobic associations, as the solution viscosity of the copolymers increased sharply with increasing polymer concentration, especially above a critical overlap concentration. An almost shear‐rate‐independent viscosity (Newtonian plateau) was also displayed at high shear rates, and typical non‐Newtonian shear‐thinning behavior was exhibited at low shear rates and high temperatures. Furthermore, the copolymers exhibited high air–water and oil–water interfacial activities, as the surface and interfacial tensions decreased with increasing polymer concentration and salinity. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2290–2300, 2003     

Hydrophobic microblock length effect on the interaction strength and binding capacity between a partially hydrolyzed microblock hydrophobically associating polyacrylamide terpolymer and surfactant

Poly(acrylamide/sodium acrylate/N‐dodecyl acrylamide)s [poly(AM/NaAA/C₁₂AM)s] with different hydrophobic microblock lengths (N_H's) were prepared by the micellar copolymerization of acrylamide and sodium acrylate with a low amount of N‐dodecyl acrylamide (0.2 mol %), and the molecular structure was characterized by Fourier transform infrared spectroscopy, ¹H‐NMR, and static light scattering. A combination of experiments involving viscosity measurement, fluorescence, and conductometry was applied to investigate the effect of N_H on the interaction strength and binding capacity between poly(AM/NaAA/C₁₂AM)s and C₁₂H₂₅SO₄Na [sodium dodecyl sulfate (SDS)]. The viscosity, I₃/I₁ (the intensity ratio of the third vibrational band to the first band of pyrene molecules), and conductivity of the mixed system of copolymers with SDS all had different variation trends with the concentration of SDS. The binding capacity of the copolymers with SDS was calculated according to quantitative differences between the critical micelle concentration of the pure SDS solution and the mixed system. All of the results show that the interaction strength of SDS with the copolymers rose, and the binding capacity decreased with increasing N_H. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40633.     

A water‐soluble CO2‐triggered viscosity‐responsive copolymer of N,N‐dimethylaminoethyl methacrylate and acrylamide

A series of copolymers PDAMs were synthesized with varying monomer ratio of acrylamide (AM) and N,N‐dimethylaminoethyl methacrylate (DMAEMA). The resulting copolymer solution shows an interesting property of viscosity‐response which is CO₂‐triggered and N₂‐enabled. Tertiary amine groups of PDAMs experience a reversible transition between hydrophobic and hydrophilic state upon CO₂ addition and its removal, which induced different rheological behavior. A combination of zeta‐potential, laser particle‐size analysis, and electrical conductivity analysis indicated that, when the monomer mole ratio of DMAEMA and AM is less than or equal to 3 : 7, the hydrophobic association structure between the copolymer molecules was destroyed by the leading of CO₂ and caused a viscosity decrease in its solution. On the contrary, when the monomer mole ratio of DMAEMA and AM is more than 3 : 7, a more extended conformation due to the protonated tertiary amine groups is formed and the enhanced repulsive interactions among the copolymer molecule results in a rise of its solution viscosity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40872.     

疏水缔合型聚合物P(AM/TA)溶液性质的研究

采用沉淀聚合法制备了疏水缔合型聚合物丙烯酰胺 /丙烯酸十四酯共聚物P(AM/TA)。研究了在链结构中引入不同疏水基团摩尔分数的共聚物的溶液性质。结果表明该共聚物在w(NaCl) =1 5 %的溶液中的黏度较之水溶液有较大提高 ,表现出明显的抗盐性质 ,而临界缔合质量分数和特性黏度均出现下降趋势。该聚合物是一种性能优异的疏水缔合型增稠剂。作者对共聚物溶液的黏度 -温度性质和剪切速度对溶液黏度的影响也进行了研究。     

Synthesis and clay stabilization of a water‐soluble copolymer based on acrylamide,modular β‐cyclodextrin,and AMPS

A modular β‐cyclodextrin copolymer for clay stabilization was prepared from 2‐O‐(allyloxy‐2‐hydroxyl‐propyl)‐β‐cyclodextrin (XBH), acrylamide (AM), 2‐acrylamido‐2‐methyl propane sulfonic acid (AMPS), and sodium acrylate (NaAA) via redox free‐radical copolymerization. The effects of reactive conditions (such as initiator concentration, monomer ratio, reaction temperature, and pH) on the apparent viscosity of the copolymer were investigated and the optimal conditions for the copolymerization were established. The copolymer obtained was characterized by infrared spectroscopy, scanning electron microscope, viscosity measurements, rheological measurement, core stress test, and X‐ray diffractometry. The crystalline interspace of MMT could be reduced from 18.95323 Å to 15.21484 Å by copolymer AM/NaAA/AMPS/XBH. And this water‐soluble copolymer also showed remarkable anti‐shear ability, temperature resistance, and salt tolerance (1000 s^?1, viscosity retention rate: 35%; 120°C, viscosity retention rate: 75%; 10,000 mg/L NaCl, viscosity retention rate: 50.2%; 2000 mg/L CaCl₂, viscosity retention rate: 48.5%; 2000 mg/L MgCl₂, viscosity retention rate: 42.9%). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Study of P(AM‐NVP‐DMDA) hydrophobically associating water‐soluble terpolymer

A new kind of hydrophobically associating water‐soluble terpolymer P(AM‐NVP‐DMDA) was synthesized by free radical terpolymerization. Compared with micellar terpolymerization, this terpolymerization can be conducted in aqueous solution in absence of external surfactant, because the hydrophobic monomer is surface active. Synthesis, structure, and solution properties of P(AM‐NVP‐DMDA) terpolymer were studied, including its electrolyte effect, rheological behavior, temperature dependence of viscosity, dilute solution property, and the polymer–alkali, polymer–surfactant interaction. The terpolymer shows strong hydrophobic effect, and the terpolymer aqueous brine solution exhibits high viscosity at low polymer concentration. Incorporation of N‐vinyl‐pyrrolidone into the terpolymer causes an improvement in thermal stability of the terpolymer. The transmission electron photomicrograph analysis of the terpolymer indicates that the presence of the microphase separation of the terpolymer in aqueous solution plays an important role in the viscosification efficiency of the terpolymer. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 211–217, 1999     

Solution and interfacial behavior of hydrophobically modified water-soluble block copolymers of acrylamide and N-phenethylacrylamide

Hydrophobically modified water-soluble block copolymers were prepared by aqueous micellar copolymerization of acrylamide and small amounts (2 and 3 mol %) of a hydrophobe (N-phenethylacrylamide) that is characterized by a long spacer that places the aromatic ring far away from the backbone, with the objective of investigating the copolymers' rheological behavior and surface and interfacial activities under various conditions such as polymer concentration, shear rate, temperature, and salinity. As expected, the block copolymers exhibit improved thickening properties attributed to intermolecular hydrophobic associations as the solution viscosity of the copolymers increases sharply with increasing polymer concentration. Additional evidence for intermolecular association is provided by the effect of NaCl, the presence of which substantially enhances the viscosity. An almost shear rate–independent viscosity (Newtonian plateau) is also exhibited at high shear rate and a typical non-Newtonian shear thinning behavior appears at low shear rates and high temperatures. Furthermore, the block copolymers exhibit high air–liquid surface and liquid–liquid interfacial activities as the surface and interfacial tensions decrease with increasing polymer concentration, indicating strong adsorption of the copolymer at the interface. The surface and interfacial tensions exhibited by the copolymers were found to be relatively insensitive to the concentration of salt (NaCl). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 467–476, 2001     

pH‐responsive polyzwitterions: A comparative study of acrylamide‐based polyampholyte terpolymers and polybetaine copolymers

A comparative study of pH‐responsive polyzwitterions (PZs) with polyampholyte or polybetaine architectures was conducted with well‐defined model polymer systems. Low‐charge‐density PZs, including ampholytic terpolymers composed of acrylamide (AM), sodium 3‐acrylamido‐3‐methylbutanoate, and (3‐acrylamidopropyl)trimethylammonium chloride and carboxybetaine copolymers composed of AM and 3‐(3‐acrylamidopropyldimethylammonio)propionate, were prepared via free‐radical polymerization in 0.5M NaCl to yield ter‐ and copolymers with random termonomer and comonomer distributions. Sodium formate was used as a chain‐transfer agent during the polymerizations to eliminate the effects of the monomer feed composition on the degree of polymerization (DP) and to suppress gel effects and broadening of the molecular weight distributions. The polymer compositions were determined via ¹³C‐NMR spectroscopy, and the residual counterion content was determined via elemental analysis for Na⁺ and Cl^?. The molecular weights (MWs) and polydispersity indices (PDIs) were determined via size exclusion chromatography/multi‐angle laser light scattering (SEC–MALLS); the polymer MWs ranged from 1.4 to 1.5 × 10⁶ g/mol, corresponding to DPs of 1.6–1.9 × 10⁴ repeat units, with all the polymers exhibiting PDIs less than or equal to 2.1. The intrinsic viscosities determined from SEC–MALLS data and the Flory–Fox relationship agreed with the intrinsic viscosities determined via low‐shear dilute‐solution viscometry. Data from the SEC–MALLS analysis were used to analyze the radius of gyration/molecular weight (R_g–M) relationships and the Mark–Houwink–Sakurada intrinsic viscosity/molecular weight ([η]–M) relationships for the PZs. The R_g–M and [η]–M relationships and viscometric data revealed that under size exclusion chromatography conditions, the poly[acrylamide‐co‐3‐(3‐acrylamidopropyldimethylammonio)propionate] betaine copolymers had more open, random‐coil conformations and greater polymer–solvent interactions than the ampholytic poly[acrylamide‐co‐sodium 3‐acrylamido‐3‐methylbutanoate‐co‐(3‐acrylamidopropyl)trimethylammonium chloride] terpolymers. The pH‐ and salt‐responsive dilute‐solution viscosity behavior of the PZs was examined to assess the effects of the polymer structure and composition on the solution properties. The polyampholyte terpolymers had greater solution viscosities and more pronounced stimuli‐responsiveness than the polybetaine copolymers because of their stronger intramolecular interactions and increased chain stiffness. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 24–39, 2004     

Synthesis and solution properties of fluorocarbon‐modified poly(N,N‐dimethylacrylamide)

Poly(N,N‐dimethylacrylamide) (PDMA) containing perfluoro‐octyl pendent groups was prepared by solution polymerization of N,N‐dimethylacrylamide in benzene with 0.16 –1.25 mol% 2‐(N‐ethylperfluoro‐octane sulfonamido) ethyl acrylate (FX‐ 13®) or 2‐(N‐ethylperfluoro‐octane sulfonamido) ethyl methacrylate (FX‐14®). The copolymer intrinsic viscosity strongly decreases with increasing comonomer content due to intramolecular association. However, the Huggins constant increases more than 40‐fold with increasing comonomer content, indicating that intermolecular association increases with increasing comonomer content. Strong Brookfield viscosity enhancements are observed above a critical copolymer concentration varying between 0.5 and 2.0 wt% depending on comonomer type and content. Some of the copolymers show pseudoplastic behaviour whereas others show shear‐thickening or both types of behaviour. These observations are consistent with competing inter‐ and intramolecular micellar association. Fluorescence studies using a perfluorocarbon‐substituted pyrene as a probe indicate the formation of hydrophobic microdomains formed by the association of perfluorocarbon groups. © 2001 Society of Chemical Industry     

Hydrophobically modified poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate): synthesis and viscosity of aqueous solution

BACKGROUND: Hydrophobically modified polyelectrolytes are widely used polymers due to their good water solubility, stretched configuration in water and strong hydrophobic association. The study reported here aimed at researching the double action of hydrophobic association and electrostatic effect of novel hydrophobically modified polyelectrolytes in solution. RESULTS: A series of novel hydrophobically modified polyelectrolytes were synthesized by micellar copolymerization with various feed ratios of sodium 2‐acrylamido‐2‐methylpropanesulfonate, N‐n‐dodecylamine and sodium dodecylsulfonate. Their structure was characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance and gel permeation chromatography, and the viscosities of their aqueous and salt solutions were studied. CONCLUSION: The results show that the addition of the hydrophobic comonomer results in a decrease in molecular weight (M_w). The smaller the initial number of hydrophobes in one micelle, the higher is M_w of the resulting copolymer. The viscosity of PAD‐1.73 polyelectrolyte is less sensitive to salt than those of the others. According to the zero shear viscosity and corresponding concentration, the critical cluster‐forming concentration, critical overlap concentration and critical entanglement concentration of these polymer solutions were determined. Moreover, in the dilute regime the viscosity decreases with increasing salinity, while in the semi‐dilute regime the viscosity decreases first and then increases. It is suggested that in dilute and semi‐dilute regimes, hydrophobic intramolecular association and intermolecular association dominate, respectively. Copyright © 2009 Society of Chemical Industry     

Synthesis,characterization, and properties of amphiphilic block copolymer of acrylamide‐styrene by self‐emulsifying microemulsion method

The copolymerization system of acrylamide (AM) and styrene (St) was acquired by using amphiphilic block copolymer PAM‐b‐PSt with lower molecular weight as polymeric surfactant, and then the microemulsion phase diagram was drawn. The appropriate copolymerization systems were chosen in the phase diagram, and higher molecular weight amphiphilic block copolymers PAM‐b‐PSt were prepared by self‐emulsifying microemulsion method. The chemical composition and structure of the products were analyzed by FTIR, ¹H‐NMR, ¹³C‐NMR, GPC, and UV; the block structure of products was characterized by DSC, and the hydrophobic association property of the products was studied by the fluorescence probe and rotating viscosity measurement. The results showed that O/W microemulsion was also acquired by using the polymeric surfactant; 3 g polymeric surfactant was only used to disperse 0.25 g St into aqueous solution, which showed higher emulsifying efficiency. At the same time, the use of self‐emulsifying microemulsion copolymerizing system can avoid back treatment of small molecular surfactant and the purified block polymer was prepared in one step; the prepared copolymers have good hydrophobic association properties and their aqueous solution showed evident viscosity increment. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Resultant synergism in the shear resistance of acrylic pressure‐sensitive adhesives prepared by emulsion polymerization of n‐butyl acrylate/2‐ethyl hexyl acrylate/acrylic acid

Acrylic emulsion pressure‐sensitive adhesives (PSAs) were synthesized by the copolymerization of n‐butyl acrylate with various levels of 2‐ethyl hexyl acrylate (2EHA) and a small constant amount of acrylic acid. The effect of varying the n‐butyl acrylate/2EHA monomer composition on the kinetic behavior of the polymerization and the characteristics of the copolymers prepared in a batch process were investigated. The results showed that increasing the amount of 2EHA in the monomer caused the polymerization rate and the glass‐transition temperature of the acrylic copolymers to decrease. Increasing the amount of 2EHA caused the gel content of the copolymers to decrease, reaching a minimum at 50 wt %; thereafter, the gel content increased at higher 2EHA levels. For the acrylic emulsion, the peel‐fracture energy of the PSAs decreased as the amount of 2EHA in the monomer was increased up to 50 wt %. At higher 2EHA levels, the peel‐fracture energy was relatively constant. Interestingly, a synergistic effect of increased shear resistance at 25 wt % 2EHA was observed without a significant trade‐off in terms of the peel and tack properties. This behavior was attributed to a good interconnection between the microgels and the free polymer chains inside the contacting particles in the adhesive film. Cooperation between various levels of 2EHA in the copolymer structure simultaneously changed the crosslink molecular weight (M_c) of the microgels and the entanglement molecular weight (M_e) of the free chains in the adhesive network morphology. The adhesive performance of the PSAs was found to be correlated with their M_c/M_e values as the 2EHA proportion was varied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and caracterization of macromonomers of poly (2-methyl-2-oxazoline)-allyl by an acid exchanged clay as eco-catalyst

The different polymer networks were constructed by two kinds of associations, one is host-guest inclusion between P(AM/A-β-CD/NaA) and P(AM/BHAM/NaA), and the other is hydrophobic association of P(AM/BHAM/NaA). Under the high-speed shearing, the viscosity survival and recovery rate of different systems were investigated. The results show the inclusion complex (CD:BHAM = 2:1) has excellent shearing resistance performance, and it was also verified by dynamic light scattering (DLS). This is mainly because the strength of inclusive association is stronger than that of hydrophobic one. The conclusion was proved by time-temperature superposition as well. It shows that the activation energy E _a of the inclusion complex (CD:BHAM = 2:1), which represents the strength of association, has a maximum value, while the activation energy E _b of P(AM/BHAM/NaA) has also a maximum one because of the multiple associative sites of hydrophobic associations. The activation energy values of the inclusion complex (CD:BHAM = 1:1) are intermediate since there are two kinds of associations in this solution. This is exactly the reason that the complex (CD:BHAM = 1:1) has the best emulsifying property. Moreover, the conclusions related to emulsifying property have been verified by using a laser particle size analyzer and Turbiscan lab stability.     

Study on the morphology of the novel hydrophobically associative acrylamide‐based terpolymer in aqueous solution by AFM measurements

The synthesized hydrophobically associating water‐soluble polymer P(AM‐BST‐NaAMPS) (PASA) exhibits good viscosification properties in the aqueous and brine solution. To study the viscosifying mechanisms of the polymer in the aqueous solution and brine solution, atomic force microscope (AFM) was applied to observe the micromorphology of the polymer solution. The AFM measurements show that continuous network structures have been formed in the aqueous solution of 0.05 g dL^?1 PASA, and with the increase in PASA concentration, the network structures become much bigger and more condensed. The network structures of PASA are collapsed by the addition of salt, and tree‐like crystals are formed, leading to the decrease in the apparent viscosity of PASA solution. However, by increasing the NaCl concentration or the polymer concentration in the brine solution, the sizes of crystals increase. These results are consistent with the ESEM and viscosity study results. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3996–4002, 2006     

Optical and electronic properties of 3,4‐dialkylthiophene‐based p‐/n‐alternating copolymers

Four novel highly soluble p‐/n‐poly[(2,5‐divinyl‐3,4‐dialkylthiophene)‐alt‐2,6‐pyridine] (PA₂TV‐Py) and poly[(2,5‐divinyl‐3,4‐dialkylthiophene)‐alt‐(2,5‐diphenyl‐1,3,4‐oxadiazole)] (PA₂TV‐OXD) are prepared by Heck coupling approach to compare their photoelectric properties. Characterizations of the copolymers include FT‐IR, ¹H‐NMR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), UV–vis spectroscopy, photoluminescence (PL), and electroluminescence (EL). Four alt‐copolymers exhibit excellent solubility in common organic solvents (e.g., CHCl₃, THF) and good thermal stabilities, losing less than 5% on heating to ～ 250°C. The optical properties depict that the band‐gap energy of PA₂TV‐Py and PA₂TV‐OXD is similarly, ranging from 2.68 to 2.80 eV in solid film and 2.90–2.97 eV in CHCl₃ solution. PA₂TV‐Pys can emit bright turquoise light with quantum efficiencies (QE) of 30.6 and 53.9%, which about 10‐18 times higher than that of homopolymer in CHCl₃ solution. Furthermore, the QE of two PA₂TV‐OXDs (purple fluorescence) are increased to 43.6 and 68.5%, respectively, about 1.3–1.4 times higher than that of PA₂TV‐Pys. Electrochemical results indicate that the electron affinity (E_a) of four alt‐copolymers range from 2.79 to 3.09 eV, which are propitious to electrons injecting and transporting from the cathode. As a result, these novel copolymers present expected good electroluminescence(EL) performance in their single layer polymer light‐emitting device (PLED) with configuration of ITO/polymer/Al, which turn‐on voltages are between 4.0 and 5.8 V and emit bright green–yellow (538 nm) and yellow (545–552 nm) EL light. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Use of a CO2‐switchable hydrophobic associating polymer to enhance viscosity–response

A series of copolymers, poly(acrylamide)‐co‐poly(N,N‐dimethylaminoethyl methacrylate)‐co‐poly(N‐cetyl DMAEMA) (abbreviation PDAMCn), was synthesized with different monomer ratios. The resulting copolymer solution shows pronounced viscosity–response property which is CO₂‐triggered and N₂‐enabled. Electrical conductivity experiment shows that tertiary amine group on DMAEMA experiences a protonate and deprotonate transition upon CO₂ addition and its removal. In addition, different incorporation rates of DMAEMA leads to two kinds of morphological change in the presence of CO₂ and thus induces different rheological behaviors. PDAMCn incorporating longer hydrophobic monomer (C₁₈DM) show more pronounced initial viscosity and higher critical stress required to cause network deformation, which consequently enhances the viscosity–response property of the solution. The addition of NaCl could also tune the viscosity of PDAMCn solution. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41468.     

Solution properties of anionic hydrophobic association polyacrylamide modified with fluorinated acrylate

The anionic hydrophobic association polyacrylamide (AFPAM) modified with fluorinated acrylate have been synthesized of acrylamide (AM), 2-acrylamide-2-methyl propanesulfonic acid (AMPS) and 2-(perfluorooctyl)ethyl acrylate (FEA) by free radical micellar copolymerization in aqueous solution utilizing sodium dodecyl sulfate(SDS) as the surfactant and potassium persulfate(KPS)/sodium bisulfite(SBS) as the redox initiator. The solution properties of these polymers were investigated. The results show that there are strong hydrophobic associations in the AFPAM aqueous solution. The intrinsic viscosity decreases and Huggins constant increases with the increase of hydrophobic FEA content. The addition of NaCl and CaCl₂ results in an increase of solution viscosity which indicate the good salt-resistant performance. The polymers exhibit good temperature tolerance property, shear-thickening and thixotropy behavior. Additionally, the AFPAM has higher surface activity in salt solution than in water.     

A novel hydrophobically associating polyampholytes of poly(AM/AA/AMQC12): preparation,characterization, and solution properties

A novel hydrophobically associating polyampholytes of poly(AM/AA/AMQC12) were synthesized by the free radical copolymerization of acrylamide (AM), acrylic acid (AA), and dimethyldodecyl(2-acrylamidoethyl)ammonium bromide (AMQC12) in water without any surfactants (named AAQ series). The structures of polymers were confirmed by ¹H NMR and ¹³C NMR. The molecular weight and polydispersity were obtained using gel permeation chromatography (GPC). The hydrophobically associated properties of polymer solution were characterized by rheology, steady-state fluorescence probe, and ¹H NMR relaxation time (T ₂). Isoelectric points (IEPs) of polymer solution were determined by the effect of pH on viscosity below critical association concentrations (cac), and the reduced viscosities of samples at IEPs were increased in the presence of NaCl. Moreover, the steady-shear viscosity of sample at IEP was also greatly enhanced in NaCl solutions when the polymer concentration is above the cac. Meantime, the storage modulus and the loss modulus of copolymers showed that the sample behaved as gel in salt media.