Rheological behaviors and structure of hydrophobically associating AM–SMA copolymers synthesized by microemulsion polymerization

A series of hydrophobically associating copolymers of acrylamide and hydrophobic stearyl methacrylate as comonomers were prepared by microemulsion polymerization. The rheological properties of the copolymers in aqueous solution depended on the content of hydrophobic monomer, initiator amount, surfactant concentration, the copolymer concentration and the addition of salt. The hydrophobically associating copolymers showed good temperature, shear, and salt resistance with the critical aggregation concentration around 0.6 g dL^?1. In addition, the apparent viscosities of hydrophobically associating copolymer solutions are increased remarkably by the addition of a small amount of NaCl and CaCl₂, respectively. FTIR and ¹H-NMR spectra indicate the structure of hydrophobically associating copolymers. The shear-thinning behavior of hydrophobically associating copolymer makes it useful in enhanced oil recovery and drilling fluids.     

水溶性疏水缔合聚合物单体的合成

水溶性疏水缔合聚合物含有大量的亲水基团和少量的疏水基团,疏水基团间的疏水缔合作用使这种聚合物具有独特的增粘、抗剪切、耐温和耐盐的溶液性能,通常采用亲水单体和疏水单体共聚制备这类聚合物。对常用亲水单体AMPS及各类疏水单体如季铵盐不饱和单体AMPDAC和DAMAB、长链丙烯酸酯,N-烷基丙烯酰胺和N-芳烷基丙烯酰胺的合成进行了综述。     

疏水改性阳离子高分子絮凝剂P（AM—DMC—CnDMB）的合成与性能研究

以丙烯酰胺（AM）、甲基丙烯酰氧乙基三甲基氯化铵（DMC）、疏水单体CnDMB为原料,通过自由基水溶液共聚合法制备了疏水改性阳离子絮凝剂P（AM—DMC—CnDMB）,考察了不同合成工艺条件下得到的不同结构的聚合产物的絮凝性能。研究结果表明,疏水单体为C4DMB和C8DMB、疏水单体含量为1mol％、絮凝剂加量为20mg／L时,综合絮凝效果较好。用所制备的疏水改性阳离子絮凝剂和普通阳离子型絮凝剂P（AM—DMC）处理城市生活污水,结果发现,疏水改性阳离子型絮凝剂处理效果优于阳离子型絮凝剂。     

Effect of hydrophobic group on flocculation properties and dewatering efficiency of cationic acrylamide copolymers

Three kinds of hydrophobically modified copolymers of acrylamide with 3-acrylamido-2-hydroxypropyltrialkylammonium chloride were prepared, in which alkyls were ethyl, butyl and octyl, respectively. The conformations of the hydrophobically modified copolymers were studied using TEM micrograph. The flocculation performances and the dewatering efficiencies were investigated. The results showed that the hydrophobic group could enhance the flocculation properties. The longer the hydrophobic alkyl chain was, the better the flocculation result was. Compared with poly-diallyldimethyl ammonium chloride (PDADMAC) and poly-acrylamide (PAM), the hydrophobically modified polymers showed better performances in turbidity removal and were quite more efficient in dewatering examination.     

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.     

基于香豆胶的疏水改性阴离子聚电解质溶液性能

将十二烷基（Dod）与十六烷基（Cet）以酯键方式分别引入经羧甲基化改性的香豆胶大分子骨架上,制备了基于香豆胶的疏水改性阴离子聚电解质衍生物（HmCmFG）。通过荧光探针芘的激发光谱、发射光谱以及紫外光谱研究了HmCmFG溶液中的疏水缔合行为,研究发现,此疏水缔合行为受到HmCmFG大分子上烷基链长与取代度以及溶液中小分子电解质NaCl的显著影响,增加烷基链长、提高烷基取代度或增大NaCl浓度均有利于溶液中疏水缔合微区的形成。采用黏度法研究了溶液中HmCmFG大分子与NaCl、表面活性剂十六烷基三甲基溴化铵（CTAB）及十二烷基硫酸钠（SDS）的相互作用。结果表明,Dod取代度小于5.7时,NaCl的加入以增强HmCmFG分子间缔合为主,溶液黏度增加,加入CTAB对于Dod取代度小于5.7时的溶液黏度值的影响高于SDS;Dod取代度为10.2或Cet取代度为6.3时,加入NaCl、CTAB或SDS后使HmCmFG分子内缔合占优势,溶液黏度降低。     

Rheological evaluation of synthesized template‐hydrophobically modified acrylamide based copolymers in brine

The newly hydrophobically modified associating acrylamide‐based copolymers were prepared by the inverse miniemulsion polymerization method in order to investigate the copolymers rheological and associating properties in water and brine solutions. Dimethyldodecane (2‐acrylamidopropyl) ammonium bromide (DDPAB) was synthesized and used as a hydrophobic monomer and was later copolymerized with acrylamide in the presence of poly(acrylic acid‐co‐maleic acid) and various molecular weights of poly(acrylic acid) as templates. The chemical compositions and functional groups of the resulting hydrophobic monomer and copolymers were characterized using the ¹H nuclear magnetic resonance and Fourier transform‐infrared spectroscopy. According to the studies on the solutions viscosity behavior, incorporation of small amount of hydrophobic monomer improved the thickening properties due to the intermolecular hydrophobic association. The apparent viscosity of the copolymers with a template was much greater than those prepared without a template. The molecular weight of the template strongly influenced the thickening behaviors of the copolymers. A template copolymer with 1 mol % of a hydrophobic monomer was the one most efficient. The addition of electrolyte saline improved the polarization of the solutions and enhanced the thickening ability. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43588.     

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。     

Rheology control by modulating hydrophobic and inclusion associations in modified poly(acrylic acid) solutions

The rheology of modified poly(acrylic acid) (PAA) solutions can be tuned by controlling the inclusion interactions between α-cyclodextrins and alkyl hydrophobes. We demonstrate three modes of control: (1) using free cyclodextrins (CD) to displace hydrophobe-hydrophobe association in hydrophobically modified poly(acrylic acid) (HMPAA) polymers—which reduces fluid viscosity, (2) using competitive inclusion interactions where stronger SDS:CD binding can be used to ‘unmask’ CD:hydropobe inclusion interactions—which increases viscosity, and (3) employing HMPAA inclusion interactions with CD groups grafted to PAA chains (CDPAA)—which produces higher viscosities than purely hydrophobic association systems at the same concentration. The inclusion association between alkyl side-group in HMPAA and CD, either free or grafted onto PAA, obeys a 1-to-1 stoichiometry at low polymer concentrations (<1 wt%). In contrast to purely hydrophobically associating polymers, the CD:hydrophobe interaction is only binary, and, therefore, these associated networks should be ideal model systems to test theoretical predictions for associative fluids.     

疏水缔合型聚丙烯酰胺的研究进展

疏水缔合型聚丙烯酰胺（HAPAM）是疏水缔合水溶性聚合物（HAWSP）中研究最多的一种,它可以通过共聚反应在聚丙烯酰胺中引人少量疏水基团而得到。由于疏水基团的憎水作用,共聚物水溶液中产生分子间缔合作用,从而具有独特的流变性能。在石油开采、污泥处理、涂料工业及生物医学等方面具有良好的应用前景。综述了国内外学者在HAPAM的合成、性质和应用等方面的研究进展,并对其发展前景进行了展望。     

Solution microstructure of a micro-crosslinked acrylamide-based terpolymer

The hydrophobically associating copolymer poly (acrylamide/butyl styrene/sodium 2-acrylamido-2-methylpropane sulphonate) (PASA) is micro-crosslinked with a small amount of phenolic aldehyde (PL) to obtain the micro-crosslinked polymer PASA–PL with excellent liquidity and water solubility. After crosslinked, the critical association concentration of copolymer reduces in the brine solution with high NaCl concentration and PASA–PL displays much better thickening and anti-aging properties in brine solutions at low polymer concentrations. The contribution of micro-crosslink of PASA with PL to the associating structures is investigated by fluorescent probe and scanning electron microscope (SEM). The fluorescent probe results show that a large amount of hydrophobic microdomains with very strong non-polarity are formed because of greatly strengthened intermolecular hydrophobic association for the PASA–PL polymer in aqueous and brine solutions, and PASA and NaCl concentration greatly influence intermolecular hydrophobic association in PASA–PL brine solutions. SEM measurements show that continuous associative structures with huge sizes are formed in PASA–PL aqueous and brine solution.     

Copolymers of N‐alkyl‐ and N‐arylalkylacrylamides with acrylamide: influence of hydrophobic structure on associative properties. Part II: rheological behaviour in semi‐dilute solution

BACKGROUND: Hydrophobically associating water‐soluble polymers are of great interest because they possess unique rheological behaviour that results from the reversible association/dissociation process of their hydrophobic moieties. In this study, we focused on the structure of hydrophobic monomers related to the rheological and viscoelastic behaviours in semi‐dilute solutions of acrylamide polymers modified with small amounts of N‐alkyl‐ and N‐arylalkylacrylamides (0.5 and 1 mol%). RESULTS: Associative efficiency increases with the length of the graft alkyl chain, with its proportion in the copolymer and with the presence of an aromatic group at the end of the alkyl graft chain. Introduction of hydrophobic groups induces a slowing down of the dynamics of the system, particularly marked for copolymers containing phenyldecyl chains. CONCLUSION: At low frequencies, solutions behave as Newtonian liquids; at higher frequencies, solutions of strongly associative systems behave as a solid with a storage modulus higher than the loss modulus and little dependency on the frequency. The system is a transient network whose dynamics depend on entanglements and hydrophobic associations. The presence of the hydrophobic groups induces an increase of the final relaxation time, even more pronounced since these associations are strong. Copyright © 2008 Society of Chemical Industry     

疏水缔合型阳离子聚丙烯酰胺的溶液性能与应用研究

以丙烯酰胺(AM)、二甲基二烯丙基氯化铵(DMDAAC)、丙烯酸十八酯(OA)为单体,用氧化-还原引发体系,通过自由基胶束共聚法制得疏水缔合型阳离子共聚物PADO。研究了共聚物组成对PADO溶液性能的影响,以及PADO对造纸中段废水的絮凝效果。结果表明,PADO水溶液中存在强烈的分子间缔合作用,在处理造纸中段废水时,其应用效果优于聚合硫酸铁、聚合氯化铝和非离子PAM。     

Synthesis and solution properties of poly(acrylamide-styrene) block copolymers with high hydrophobic content

Hydrophobically associating block copolymers of polyacrylamide/styrene with a high hydrophobe content were synthesized using micellar copolymerization under various conditions of surfactant and initiator concentrations with the objective of determining the conditions that produce optimum solution properties for enhanced oil recovery. Solubilities, aqueous solution viscosities and interfacial properties with air and oil of the copolymers were investigated. The influence of salt on the solution properties was also studied. Nature of hydrophobic sites and onset of hydrophobic association were studied by measuring the fluorescence of pyrene in polymer solutions. Optimum solution properties were obtained for copolymers synthesized under conditions of high surfactant and initiator concentrations. The copolymers displayed substantial thickening properties at low concentrations with enhanced thickening in the presence of salt. The interfacial tensions of the aqueous solutions with n-decane and air were also reduced. Interfacial properties were slightly sensitive to salt concentration. The copolymer solutions showed shear and temperature thinning behaviors typical of polymer solutions.     

AM/AMPS/SMA三元共聚物的合成及其性能研究

采用自由基胶束聚合法制备了丙烯酰胺/甲基丙烯酸十八酯/2-甲基-2-丙烯酰胺基丙磺酸三元疏水缔合共聚物(HAPAM),系统研究了HAPAM水溶液的流变行为。结果表明,在聚丙烯酰胺大分子主链上引入阴离子基团和疏水基团后。阴离子的电粘效应与疏水基团的疏水缔合作用相互协同作用,使得共聚物水溶液的粘度明显提高;盐溶液对疏水缔合作用的增强效应与阴离子基团的耐盐性相互结合,使HAPAM水溶液的抗盐性能得以明显提高;HAPAM在水溶液中可以有效的形成大量疏水微区,因而具有较好的耐温耐盐和增粘性能。     

Autoassociative natural polymer derivatives: the alkylchitosans. Rheological behaviour and temperature stability

Chitosan may be chemically modified by reductive amination leading to the grafting of hydrophobic alkyl chains along the hydrophilic macromolecular chain. This allows to obtain amphiphilic polymers whose the hydrophobicity (or the hydrophile-lipophile balance, HLB) may be adjusted according to the length of the grafted alkyl chain or the degree of substitution of the amine functions. The existence of hydrophobic interactions between the alkyl chains will change the physico-chemical properties of the solutions of the modified chitosans. These properties are studied and the study is particularly focused on the influence of the polymer concentration and temperature on them and applications as rheology modifiers. Threshold concentrations, over which the polymer solutions have peculiar temperature behaviour, were defined. According to their structure it is possible to prepare solutions with constant viscosity or increasing one with temperature.     

Rheological properties of semidilute solutions of poly(acrylic acid) modified with hydrocarbon and fluorocarbon end‐capped poly(ethylene glycol) macromonomer

Hydrocarbon and fluorocarbon end‐capped poly(ethylene glycol) (PEG) macromonomers with 9, 23, and 45 ethylene oxide units were synthesized by the esterification method. Copolymerization of these macromers with acrylic acid (AA) resulted in hydrophobically grafted poly(AA)s (PAAs) containing different lengths of PEG spacers. Their solution properties were investigated by rheological measurements and compared to those without hydrocarbon and fluorocarbon groups and without PEG spacers. Evident hydrophobic association was found to exist in the aqueous solution of these hydrophobically grafted copolymers, and the associating efficiency was improved by the flexible PEG spacer compared to those counterparts without them. However, the intramolecular association became predominant with the spacer length increase and the solution viscosity decreased. A wide viscosity plateau was observed for macromer modified polyelectrolytes in the alkalization process, which was unavailable for hydrophobically modified ones without PEG spacers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 12: 2777–2783, 2003     

Rheological Behaviour of Poly (Acrylamide-G-Propylene Oxide) Solutions: Effect of Hydrophobic Content,Temperature and Salt Addition

Abstract

The viscosity of hydrophobically modified polyacrylamide was investigated as a function of polymer concentration in aqueous and in salt solutions, and also as a function of temperature. The graft copolymers were constituted of polyacrylamide backbone and different amount of hydrophobic polypropylene oxide) graft chains. Measurements of intrinsic viscosities have been performed by using a Contraves low-shear LS-40 rheometer. From these results, a dependence of the intrinsic viscosity of the polymer solution with the molecular weight was observed, where an increase of the latter resulted in higher intrinsic viscosity. In this case, the effect of the molecular weight was more emphasized than the effect caused by the slightly different degrees of hydrophobic incorporation. When enhancing the temperature, it was not verified a significant change on the reduced viscosities of the copolymer solutions and the graft chain length was also observed.     

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.     

Synthesis and swelling behaviour of hydrophobically modified responsive polymers in dilute aqueous solutions

New series of associating polymers were synthesised in order to investigate opposite behaviours of hydrophobically modified water-soluble polymers and thermoresponsive water-soluble polymers carrying LCST stickers. On the basis of a poly(acrylic acid) backbone, amino-terminated poly(N-isopropylacrylamide), poly(ethylene oxide-co-propylene oxide) and/or dodecyl chains were grafted following a reaction of condensation activated by carbodiimide. Two homologous series of well-defined single grafted and double grafted copolymers were obtained, with double grafted chains containing both C12 and LCST grafts. The dilute solution properties of these copolymers were carefully studied by capillary viscometry. At low salt concentration and below the LCST of the grafts, the swelling properties of macromolecular chains are controlled either by intramolecular associations between hydrophobes, excluded volume effect exerted by hydrophilic grafts or by a balance between these opposite interactions. The deswelling of macromolecular chains, induced by hydrophobic interactions, is amplified at higher ionic strength and more particularly above the transition temperature of the side chains.