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.     

A novel flocculant of Al(OH)3-polyacrylamide ionic hybrid

A novel flocculant based on hybrid Al(OH)(3)-polyacrylamide (HAPAM) has been synthesized using a redox initiation system ((NH(4))(2)S(2)O(8)-NaHSO(3)) at 40 degrees C in aqueous medium. The HAPAM was characterized by viscometry, IR spectroscopy, TEM, conductivity, and TGA. The flocculation behavior for 0.25 wt% kaolin suspension was evaluated by spectrophotometry and phase contrast microscopy. It was found that an ionic bond exists between Al(OH)(3) colloid and polyacrylamide (PAM) chains in the HAPAM and the flocculation efficiency of HAPAM is much better than that of commercial polyacrylamide (PAM) and PAM/AlCl(3) blend.     

反相微乳液中疏水缔合型聚丙烯酰胺的合成及其性能研究

在反相微乳液体系中合成了疏水缔合型聚丙烯酰胺 (HAPAM ) ,用Brookfield旋转粘度计测定了其水溶液性能 ,并与传统胶束聚合法制备的HAPAM作了比较 .结果显示 ,前者有更优越的耐盐和抗剪切性能 ,这主要是因为前者的大分子链上疏水共聚单体呈无规分布而后者呈嵌段分布 ,其疏水分子链以分子间而不是分子内缔合为主     

An Alternative Way towards Preparation of Hydrophobically Associating Polyacrylamide:Chemical Post-Modification

Hydrophobically associating polyacrylamides (HAPAMs) are derivatives from polyacrylamides by incorporating a small amount of hydrophobic moieties along the water-soluble mainchain. They are now becoming a class of promising candidates as thickeners or rheology modifiers in the formulations where rheology is necessary to be regulated, such as tertiary oil recovery, drilling fluids, hydraulic fracturing and coatings. Due to association of hydrophobes in nano-domains, their aqueous solutions exhibit very interesting rheological properties and better stability against salts than the unmodified precursor, polyacrylamide.Generally, there are two synthetic routes to introduce hydrophobic portion onto water-soluble polymer chains; i.e., direct copolymerization of hydrophobic and hydrophilic monomers, and post-polymerization functionalization[1]. In the case of HAPAM polymers, a commonly accepted method is micellar copolymerization in which an appropriate surfactant is employed to solubilize both monomers. However, it is widely reported[2] that the obtained polymers via micellar polymerization are characterized by: (i) blocky distribution of the hydrophobes; (ii) compositional inhomogeneity and (iii) strong dependence of solution properties on the block length.In this work, the alternative process, i.e., chemical post-modification, is employed to synthesize HAPAM polymers by direct N-alkylation of parent polyacrylamide (Figure 1) in dimethyl sulfoxide[3,4].PAM HAPAMFig. 1 Schematic route to prepare HAPAM by direct N-alkylation of PAMIt is found that the final incorporation of hydrophobic groups is in good agreement with the feed ratio[4], in contrast with that from micellar copolymerization which always brings about composition drift. Furthermore, unique rheological responses to shear rate, salt, temperature are also evidenced[5].     

疏水缔合聚丙烯酰胺与双子表面活性剂的自组装

通过荧光光谱、动/静态激光光散射研究了疏水缔合聚丙烯酰胺(HAPAM)自组装行为及双子表面活性剂(双十四酸乙二酯双磺酸盐(DMES-14))对其的影响.实验结果表明:聚合物HAPAM在溶液中能够通过自组装形成疏水微区,表现出芘的发射光谱中第一振动峰(373nm)与第三振动峰(383nm)的荧光强度之比(I1/I3)值随聚合物浓度的增大而下降,当聚合物HAPAM浓度(CP)达到一定值后,I1/I3值不再变化;当加入表面活性剂时,HAPAM能够与双子表面活性剂在溶液中形成混合胶束,在聚合物浓度一定时,I1/I3值随表面活性剂浓度(CS)的增大急速下降,当表面活性剂浓度达到30mg·L-1时,I1/I3值趋于恒定;当表面活性剂浓度一定时,聚合物/表面活性剂二元体系中聚集体的聚集数随HAPAM浓度的增大出现先下降再增加的过程;一定量的双子表面活性剂对HAPAM分子间的缔合起促进作用,过量的双子表面活性剂对HAPAM分子间的缔合起抑制作用,使HAPAM的表观重均分子量(Mw,a)、均方根回转半径()和流体力学半径()随表面活性剂浓度增加先增大后减小,而HAPAM的/比值则随表面活性剂浓度增大出现一定程度的上升,表明HAPAM分子链段变得相对舒展.     

疏水改性聚丙烯酰胺的荧光研究

使用荧光探针技术,跟踪了疏水改性聚丙烯酰胺(HMPAM)在溶液中的变化过程,对HMPAM在溶液中的聚集行为进行了研究。同时也对部分水解聚丙烯酰胺(HPAM)作了对比研究。发现HMPAM在溶液中具有独特的变化规律:由疏水缔合形成超分子聚集体,再由超分子聚集体形成布满整个溶液空间网络结构的过程。并使用粘度法对其宏观流变性能进行了研究,发现两种手段所得的结果具有较好的对应关系。     

聚丙烯酰胺絮凝效果的母液浓度依赖性及其影响

考察了相同剂量下不同浓度阴离子型聚丙烯酰胺絮凝剂(PAM)母液对三氧化二铁悬浮液的絮凝效果.通过电导率和流变行为测试,阐明了随母液浓度增大絮凝效果先变好后变差的原因.研究结果表明,母液浓度为0.3 g/L时PAM絮凝效果最佳.根据聚电解质标度理论及流变测试结果,认为此最佳母液浓度(cop)接近临界缠结浓度.母液电导率及加入絮凝剂后的搅拌过程中水体电导率变化表明,絮凝剂浓度高于最佳母液浓度时出现的电荷屏蔽现象使得有效电荷减少,导致高母液浓度下絮凝效果变差.向低浓度母液中添加适量β-环糊精后,环糊精分子通过氢键作用搭桥使PAM分子间距变小,发生协同絮凝形成足够大的絮体,从而使絮凝效果得到改善.这一结果表明,低于最佳母液浓度时由于PAM分子相对孤立形成的絮体不足以沉降,是导致絮凝效果较差的原因.     

疏水缔合聚丙烯酰胺与双子表面活性剂的相互作用

制备了一种脂肪酸酯双磺酸盐型双子表面活性剂, 利用粘度法、界面张力法和原子力显微镜研究了疏水缔合聚丙烯酰胺与双子表面活性剂在溶液中的相互作用. 实验结果表明: 疏水缔合聚丙烯酰胺在溶液中能够通过自组装形成疏水微区并发展成网络结构, 疏水微区与表面活性剂在溶液中能形成混合胶束; 当一定量的表面活性剂加入时, 对疏水缔合聚丙烯酰胺的自组装起促进作用, 而过多双子表面活性剂的加入又会对聚合物分子的自组装起抑制作用, 从而显著影响疏水缔合聚丙烯酰胺的溶液性质, 随着表面活性剂浓度的增加, 聚合物溶液粘度先增加、再降低; 同时, 疏水缔合聚丙烯酰胺对双子表面活性剂的界面性能也有较大影响, 聚合物的加入使双子表面活性剂降低油/水界面张力的能力下降, 油/水界面张力达到平衡所需时间延长.     

疏水改性聚丙烯酰胺的增粘机理研究

通过与聚丙烯酰胺（PAM）对比,使用荧光光谱、紫外光谱、原子力显微镜以及流变性实验对疏水改性聚丙烯酰胺(HMPAM)的溶液行为和微观结构进行了研究.通过荧光实验I3/I1值的变化确定了HMPAM的临界缔合浓度.结合荧光、紫外及流变性实验,对HMPAM在溶液中通过疏水缔合形成疏水微区、超分子聚集体及发展到空间网络的结构变化进行了研究.用原子力显微镜证实了HMPAM溶液中网络结构的存在.对HMPAM表现出的特殊流变性从微观上找到了依据,提出了HMPAM的增粘机理.     

疏水缔合聚丙烯酰胺在盐水中的自组装行为

使用静态光散射、动态光散射以及原子力显微镜(AFM)研究了疏水缔合聚丙烯酰胺(HAPAM)在盐水溶液中的自组装行为.研究了聚合物分子在不同盐浓度中的表观重均分子量(Mw,a),均方根回转半径(),流体力学半径(),第二维里系数(A2)的变化,并根据/的比值得出聚合物分子的聚集形态.实验结果表明:随着盐浓度的增强,聚合物溶液的分子链由舒展变得卷曲.     

坡缕石/聚丙烯酰胺无机-有机杂化絮凝剂的合成、表征与应用

将酸活化坡缕石(PGS)与氯化乙醇胺(EACl)所得氯化乙醇胺改性坡缕石(PGS-EACl)与高价铈盐(Ce⁴⁺)组成氧化还原非均相引发体系,引发丙烯酰胺单体聚合得到了坡缕石/聚丙烯酰胺(PGS/PAM)无机-有机杂化物.用¹HNMR、FTIR、粘度法和电导法对杂化物进行了结构表征,表明杂化物中存在PGS^Θ⊕NH₃R离子键合作用.考察了PGS-EACl用量、聚合反应时间和单体浓度对杂化物特性粘数的影响.由PGS/PAM杂化絮凝剂分别处理高岭土和氧化铁红两种配制废水,发现杂化絮凝剂的絮凝效果明显优于纯PAM絮凝剂.     

半互穿海藻酸钠/聚丙烯酰胺凝胶吸附结晶紫动力学/热力学行为和吸/脱附机理

将含有大量—COO-的聚阴离子海藻酸钠(SA)引入聚丙烯酰胺(PAM)凝胶网络中,采用自由基溶液聚合法制备半互穿网络结构的SA/PAM水凝胶.采用扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和傅里叶变换红外光谱(FTIR)分析了SA/PAM水凝胶吸附结晶紫(CV)前后的孔洞形态和化学组成变化,采用多种模型研究了SA/PAM水凝胶对CV分子的吸附动力学和热力学行为,并探讨了脱附效率,提出了吸脱附机理.研究结果表明,SA的引入降低了孔径尺寸,增加了孔洞数量;SA/PAM-10凝胶对CV分子吸附量最大,达到13.5838 mg/g,符合伪一级吸附动力学模型,吸附速率受膜扩散和粒子内扩散过程共同影响;等温吸附过程符合Temkin和D-R模型,属于微孔多层吸附;热力学分析结果表明,吸附过程由熵驱动引起,非化学诱导因素影响所致;采用HCl进行脱附,最大脱附率高达94.18%,加入Na OH可实现SA/PAM水凝胶的可逆吸附;较高的吸附量主要源于SA分子链上的COO-与CV分子的—C N+—存在的静电作用,低pH值时由于—COO-和—NH2质子化导致与CV分子的静电斥力增大,脱附率随之增加.     

聚丙烯酰胺与混合表面活性剂的相互作用

通过粘度和紫外吸收光谱的测定，研究了ＰＡＭ与Ｒ１２ＳＯ３Ｎａ－Ｒ１１ＣＯＯＮａ混合表面活性剂之间的相互作用，结果表明，ＰＡＭ可与混合表面活性剂形成复合物，从而使体系表现出典型聚电解质的粘度行为。可能的机理是，以疏水力形成的Ｒ１２ＳＯ３＾－—Ｒ１１ＣＯＯＨ（Ｎａ）预胶束或二聚体通过ＰＡＭ－Ｒ１１ＣＯＯＨ间的氢键力相结合。进而使大分子链上带有大量负电荷，静电斥力引起大分子链伸展，因而产生电粘效应。     

Coarse-grained molecular dynamics simulation of self-assembly of polyacrylamide and sodium dodecylsulfate in aqueous solution

Coarse-grained molecular dynamics simulations have been performed to study the self-assembly of polymer, polyacrylamide (PAM) and surfactant, sodium dodecylsulfate (SDS) in aqueous solution. Our simulations revealed that PAM curled into clusters in the absence of SDS, while it was stretched if SDS was added. For the SDS-PAM complexes, the aggregate formation process can be divided into three stages: firstly, PAM quickly absorbs some SDS monomers until the radius of gyration (Rg) of polymer reaches a minimum; then, PAM stretches and the Rg of PAM increases due to more and more adsorbed SDS; ultimately, the commonly accepted "necklace" structure is formed with PAM located at the interface of the hydrophobic and hydrophilic regions of the SDS micelle. The main driving force for the association was hydrophobic interactions between the polymer backbone and the surfactant hydrophobic tails. As the concentration of SDS increased, the Rg of PAM increased up to a maximum, indicating the polymer was saturated with surfactant.     

Grafting polyelectrolytes onto polyacrylamide for flocculation 1. Polymer synthesis and characterization

Low-molecular-weight high-charge-density cationic diallyldimethylammonium chloride homopolymer (polyDADMAC) was grafted onto high-molecular-weight nonionic polyacrylamide (PAM) via a free radical mechanism using a gamma radiation technique. The graft copolymer systems were characterized in terms of viscosity, composition, gel content, degree of grafting and grafting efficiency. Degree of grafting was a strong function of radiation dose, dose rate and polyelectrolyte concentration. Gels were formed at high radiation doses and high PAM levels. Crosslinking between the electrolyte polymers was limited due to electrostatic repulsion. Gelation was mainly caused by coupling of PAM chains. High grafting efficiency was achieved: the lower the poly(DADMAC) concentration, the higher the grafting efficiency observed. The grafting mechanism and the effect of ion interactions on copolymer structural properties are also elucidated and discussed. Received: 6 April 1998 Accepted in revised form: 28 August 1998     

Solution properties of poly(acrylamide-co-3,5,5-trimethylhexane methacrylate) and its polyelectrolyte derivative

The physicochemical properties of hydrophobically modified polyacrylamide (HAPAM) containing a small amount of hydrophobic groups (3,5,5-trimethylhexane methacrylate) and its partially hydrolyzed derivative (HAPAM-10N500) were investigated. The ¹³C spectrum was used to establish the degree of hydrolysis of HAPAM-10N500. Small-angle X-ray scattering (SAXS) was employed to highlight the polyelectrolyte character of HAPAM-10N500, estimate the chain conformation in the semidilute regime, and evaluate the influence of the ionic strength and the type of salt. The weight average molecular weight, the second virial coefficient, and radius of gyration were determined by static light scattering (SLS). The polymers showed different rheological properties in aqueous solution, with significant increase in viscosity due to partial hydrolysis of HAPAM, however, with strong dependence on ionic strength of the medium. Results showed that the polymers HAPAM and HAPAM-10N500 are suitable for application in processes of moderate temperatures and salinities.     

PAM与月桂酸钠的相互作用

通过PAM/月桂酸钠(R^1 COONa)混合溶液比浓粘度和紫外-可见吸收光谱的测定, 考察了两者之间的相互作用机理。 结果表明, 在中性或弱酸性溶液中, PAM大分子可与R^1 COOH发生氢键缔合, 而R^1 COOH则以疏水力与R^1 COO^-缔合成二聚体、预胶束或胶束, 从而使PA分子链上带有大量电荷, 混合溶液表现出聚电解质的粘度行为。     

Novel hydrophobically associative polyacrylamide with tunable viscosity

Hydrophobically associative polyacrylamide(HAPAM) were prepared in aqueous solution by radical copolymerization of novel cationic surface-active monomer,dimethylhexadecyl(3-acrylamidopropyl)ammonium bromide(DMHAB),with acrylamide(AM) in the presence of DMHAB/CTAB mixed micelles.The length of hydrophobic microblock(N_H) in HAPAM is controlled by the molar fraction of DMHAB in mixed micelles,which can be mediated by the ratio of CTAB to DMHAB.The results of steady-state fluorescence probe and viscometry ex...     

疏水缔合聚丙烯酰胺在表面活性单体胶束溶液中的制备及其流变特性

配制了表面活性单体2-丙烯酰胺基十二烷磺酸钠(NaAMC12S)与十二烷基硫酸钠(SDS)的胶束溶液,分别测定了强疏水单体N-正十二烷基丙烯酰胺(C12AM)在两种胶束溶液中的增溶性能;在此基础上,于两种胶束溶液中分别进行了丙烯酰胺(AM)与C12AM的胶束共聚合,制备了疏水缔合聚丙烯酰胺(HAPAM),它们分别为二元共聚物C12AM/AM与三元共聚物C12AM/NaAMC12S/AM;测定了两种共聚物的红外光谱;采用荧光探针法与表观粘度法重点研究了它们的疏水缔合性与流变性能.结果表明,在表面活性单体NaAMC12S的胶束溶液中,可顺利地实现AM与疏水单体的胶束共聚合,由于表面活性单体也参与了共聚合,故制得的产物为三元共聚物C12AM/NaAMC12S/AM;与在SDS胶束溶液中制备的二元共聚物C12AM/AM相比,前者的疏水缔合性更强,其强疏水缔合性以强疏水单体C12AM的贡献为主,以表面活性单体NaAMC12S的贡献为辅.     

Study on Associative Polymerizable Inverse Microemulsion

In an effort to determine the suitable polymerizable inverse microemulsion region in pseudoternary phase diagram (PPD), the pseudoternary system of Span80‐Tween80/isopar M/aqueous solution of acrylamide and 2‐(methacryloyloxyl) ethyl hexadecyl dimethyl ammonium bromide (DM16) was investigated at 40°C. The PPD was obtained by a combination method of turbidimetry and conductivity (CMTC). The reliability of the PPD line was checked by investigating the state of selected experimental points near the boundary line using the Pulsed Near Infrared Light Scattering (PNILS) and centrifugation. Based on the achieved PPD, a series of hydrophobically associating polyacrylamide (HAPAM) microlatex were successfully prepared by choosing the right formulation. It shows that CMTC could be used as a good method in ascertaining a polymerizable inverse microemulsion region, from which optimized HAPAM can be prepared. The factors governing the area of the polymerizable inverse microemulsion region were also discussed.