Critical Association Concentration Research Articles

Novel, rosin‐based, hydrophobically modified cationic polyacrylamide for kaolin suspension flocculation

ABSTRACTA novel, hydrophobically modified cationic polyacrylamide (HMPAM) was synthesized via the copolymerization of acrylamide, diallyl dimethyl ammonium chloride (DMDAAC), and diallylmethyl dehydroabietic acid propyl ester ammonium bromide. Optimum conditions for preparing HMPAM were such that the amount of initiator was 0.075 wt % of the total monomer mass, the monomer concentration was 20 wt %, and the amount of DMDAAC was 18 mol % of the total monomer molar mass. HMPAM was characterized with an UV–visible spectrometer, 1H‐NMR, Ubbelohde viscometer, rotational viscometer, and rotational rheometer. HMPAM solutions exhibited strong hydrophobic associations, and the critical association concentration of the HMPAM aqueous solution was about 0.7 wt %; the HMPAM solutions also showed salt thickening and shear resistance. The surface morphologies of the freeze‐dried HMPAM samples (1 wt %) were also observed via scanning electron microscopy. Compared with unmodified cationic polyacrylamide, Synthesis of HMPAM‐0.5 exhibited a stronger flocculation capacity, and the optimal transmittance of the supernatants was above 95%. HMPAM‐0.5 showed significant flocculation performances for 3–4 and 3–5 wt % kaolin suspensions at 40 and 50 mg/L, respectively. Moreover, the flocculation performance was enhanced with the addition of NaCl and CaCl2. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46637.

Association of Chitosan in Aqueous-Alcohol Solutions

The association of chitosan in aqueous-alcohol solutions is studied via probe fluorescence spectroscopy and dynamic light scattering. It is shown that, if a certain critical concentration is reached, the associates of macromolecules 12–38 nm in size are formed in chitosan solutions. The addition of 5–60 vol % ethanol to the solvent leads to reduction in the critical association concentration. The tendency of chitosan macromolecules toward association is the most pronounced at 34 vol % alcohol.

Thermosensitive behavior of hydrophobically associating anionic guar gum solutions and gels

Herein, we describe the syntheses of novel thermoassociating anionic guar gums (TGGs) with long aliphatic and polyethylene glycol (PEG) segments and characterize these gums by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy. Additionally, we explore the properties of TGG solutions and gels by viscometry, dynamic light scattering, fluorescence spectroscopy, and rheometry, revealing the thermoresponsive behavior of these systems. Thus, TGG solution viscosity increases with decreasing PEG segment length below 35°C, with an opposite trend observed at 60°C. Similarly, the critical association concentration increases with increasing PEG segment length at room temperature, with an opposite dependence detected at 50°C. High temperature results in almost complete hydrophobization of PEG segments, endowing TGG solutions with unique thermoassociating behavior. Moreover, TGG gels feature both coordination and physical crosslinking, with the latter enhanced by increased hydrophobic group length, and therefore exhibit viscosities much higher than that of the parent sulfo-hydroxypropyl guar gum (SHG) gel. The storage moduli of TGG gels reach their maxima with increasing temperature. Additionally, the addition of NaCl increases the viscosities of TGG gels to maximum values exceeding that of the SHG gel.

Ultrasound-initiated synthesis of cationic polyacrylamide for oily wastewater treatment: Enhanced interaction between the flocculant and contaminants

Weak interaction between flocculants and oil is a main bottleneck in the treatment of oil-containing wastewater. To solve this problem, a novel flocculant PAB with cationic micro-block structure and hydrophobic groups of benzene rings was synthesized by ultrasound initiated polymerization technique and applied to remove turbidity and oil from water. To avoid unnecessary addition of reagents in traditional template and micellar copolymerization, surface-active monomer benzyl(methacryloyloxyethyl)dimethylammonium chloride (BMDAC) with self-assembly ability in aqueous solution was employed to synthesize flocculants. The critical association concentration of BMDAC measured by conductivity and surface tension methods was 0.014 mol·L−1. The results of reactivity ratio, statistical analysis of sequence-length distribution and 1H NMR provided evidence for the synthesis of copolymer with cationic micro-block. In addition, the apparent viscosity measurement indicated that PAB had an obvious hydrophobic association property. Finally, flocculation tests demonstrated that flocculation performance was greatly improved by adding PAB and the removal rate of oil and turbidity both reached the maximum (87.5% and 92%) at dosage of 40 mg·L−1 and pH of 7.0. Flocculation mechanism investigation demonstrated that the cooperation of charge neutralization, adsorption bridging, and hydrophobic association effect played an important role. The formed flocs by PAB was large, compact, difficult to break, and easy to regrow because of the enhanced interaction between flocculants and oil. In summary, this study can provide important reference in the design of organic flocculants in oily wastewater treatment applications.

Association of chitosan in the presence of an anionic surfactant in aqueous-glycerol solutions

The effect of additions of sodium tetradecyl sulfate as an anionic surfactant on the association of chitosan macromolecules in aqueous-glycerol solutions was studied by fluorescence probe spectroscopy and dynamic light scattering. Associates of 40–170 nm size are formed on reaching a certain critical concentration of chitosan in solutions. The critical association concentration of chitosan in solutions containing 10–30 vol % glycerol is higher than in aqueous solutions. Formation of chitosan–surfactant complexes enhances the tendency of chitosan macromolecules to association in water–glycerol mixed solvents.

Synthesis and properties of fluorinated hydrophobic association polyacrylamide as thickener for hydraulic fracturing fluid

A novel, anionic fluorinated hydrophobic association polyacrylamide (FAPAM) was successfully synthesized from acrylamide (AM), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylic acid (AA), and 1H,1H,2H,2H-heptadecafluorodecyl acrylate (HFA) by radical micellar polymerization using sodium dodecyl sulfonate and potassium persulfate as a surfactant and an initiator, respectively. This synthesis was confirmed by Fourier transform infrared and nuclear magnetic resonance spectroscopy techniques. The results showed that the optimal content of the added HFA monomer was 0.3–0.5% in weight to the as-prepared FAPAM, which possessed 300–400 mg L−1 of critical association concentration. The results also showed that the properties of FAPAM3-0.4 were best for the appropriate mass ratio of AM:AA:AMPS = 7:1:2. The apparent viscosity of FAPAM3-0.4 was 1350 mPa s in the aqueous solution, and the apparent viscosities of other samples were 161.5 and 148.3 mPa s when the Na+ and Ca2+ concentrations were 5000 and 2000 mg L−1, respectively. Moreover, the FAPAM3-0.4 showed excellent temperature resistance and shearing resistance, in which the apparent viscosity was approximately 478.8 mPa s at 100 °C for 120 min. The viscosity could be completely restored or even it could be slightly higher than its original value when the shearing rate decreased. The results indicated that the excellent performance of FAPAM3-0.4 may make it a potential candidate as thickener for hydraulic fracturing fluid in oil and gas fields.

Salt stimulus response of a carboxyl betaine amphoteric hydrophobic associative polyacrylamide

A carboxyl betaine amphoteric hydrophobic associative polyacrylamide (CBAHAPAM) was synthesized in water solution through radical polymerization, which was made of polyacrylamide, N,N′-dimethyl octadecyl allyl ammonium chloride (DOAC), 1-carboxy-N,N′-dimethyl-N-(3-methylacryl-amidopropyl) ethanaminium inner salt (CBMAA-1) and 2-acrylamide-2-methyl propanesulfonic acid (AMPS). Self-assembly associative properties in CBAHAPAM solution and the effects of salt and temperature on the associative behavior were investigated by the means of viscosimetry, rheological test, fluorescence spectroscopy, and environmental scanning electron microscope (ESEM). Results showed that the critical association concentration (CAC) of the CBAHAPAM was about 0.30–0.32 wt %. The addition of the calcium chloride made the apparent viscosity of CBAHAPAM solution improve drastically than NaCl. Meanwhile, CBAHAPAM solution with NaCl and CaCl2 showed up better heat and shearing resistance than CBAHAPAM solution itself. The network structures of CBAHAPAM aqueous or salt solution was observed by ESEM. NaCl and CaCl2 reinforced the network structures, which further indicated that CBAHAPAM solution had a excellent capacity of salt thickening.

Entrapment and delivery of α-tocopherol by a self-assembled, alginate-conjugated prodrug nanostructure

The aim of the study was to deliver α-tocopherol by a combination of prodrug and entrapment techniques, and to evaluate the ability of entrapped α-tocopherol to inhibit lipid oxidation in an oil-in-water emulsion. The amphiphilic alginate-α-tocopherol conjugate was synthesized via esterification reaction and confirmed by IR, 1H NMR, and fluorescence spectroscopy as well as esterase hydrolysis. The bound α-tocopherol in the conjugate was 20.6 μmol/g. The conjugate self-assembled into nanostructures in water, with a critical association concentration of 0.076 g/L. The percent entrapment and loading efficiency of α-tocopherol in the self-assembled nanostructures of the conjugate were, respectively, 4.92–16.82% and 78.83–92.32%, depending on the initial loading of α-tocopherol. Both blank and α-tocopherol-loaded nanostructures presented a negative zeta potential ranging from −50 to −65 mV and exhibited spherical shape with particle sizes in the range of 190–253 nm. More than 40% of α-tocopherol was retained after 216 h (i.e. 9 days) in phosphate buffer solutions (pH 7.4). The release of α-tocopherol was faster for nanostructures with lower α-tocopherol theoretical loading. Based on the thiobarbituric acid reactive substances assay for lipid oxidation, the blank nanostructures of the conjugate did not show antioxidant activity while the α-tocopherol-loaded nanostructures protected lipids against oxidation better than free α-tocopherol entrapped in the oil phase or in Tween 20 micelles. The results indicated that the newly prepared α-tocopherol-loaded nanostructure is a promising platform for solubilizing and delivering antioxidant activity of α-tocopherol in aqueous dispersions.

Nanoscale isoindigo-carriers: self-assembly and tunable properties.

Over the last decade isoindigo derivatives have attracted much attention due to their high potential in pharmacy and in the chemistry of materials. In addition, isoindigo derivatives can be modified to form supramolecular structures with tunable morphologies for the use in drug delivery. Amphiphilic long-chain dialkylated isoindigos have the ability to form stable solid nanoparticles via a simple nanoprecipitation technique. Their self-assembly was investigated using tensiometry, dynamic light scattering, spectrophotometry, and fluorometry. The critical association concentrations and aggregate sizes were measured. The hydrophilic–lipophilic balance of alkylated isoindigo derivatives strongly influences aggregate morphology. In the case of short-chain dialkylated isoindigo derivatives, supramolecular polymers of 200 to 700 nm were formed. For long-chain dialkylated isoindigo derivatives, micellar aggregates of 100 to 200 nm were observed. Using micellar surfactant water-soluble forms of monosubstituted 1-hexadecylisoindigo as well as 1,1′-dimethylisoindigo were prepared for the first time. The formation of mixed micellar structures of different types in micellar anionic surfactant solutions (sodium dodecyl sulfate) was determined. These findings are of practical importance and are of potential interest for the design of drug delivery systems and new nanomaterials.

Preparation and in vitro characterization of retinoic acid-loaded poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) micelles.

In order to achieve the controlled release of all-trans-retinoic acid (ATRA), poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL) copolymer with average molecular weight of 5.34 kDa was synthesized. The nanosized micelles were prepared from copolymer by nano-precipitation method. Critical association concentration (CAC) of micelles was measured by fluorimetry and results indicated low CAC value of micelles (1.9 × 10-3 g/L). ATRA was encapsulated in the core of micelles using different ratios of drug to copolymer. In the case of 10% drug to polymer ratio, more than 80% of the drug was released within 3 days, whereas for ratio of 2% more than 90% of the drug was released within 3 h. The cytotoxic study performed by MTT assay showed that H1299 survival percent decreased significantly (P ≤ 0.05) after exposure to drug-loaded micelles, while no proliferation inhibition effect was observed by either free ATRA or blank PCL-PEG-PCL micelles.

Highly Stable Fluorinated Nanocarriers with iRGD for Overcoming the Stability Dilemma and Enhancing Tumor Penetration in an Orthotopic Breast Cancer.

The stability dilemma and limited tumor penetration of nanocarriers in cancer chemotherapy remain two predominant challenges for their successful clinical translation. Herein, the pH-sensitive fluorocarbon-functionalized nanocarriers (SFNs) with a tumor-homing and penetrating peptide iRGD are reported to overcome the stability dilemma and enhance tumor accumulation and penetration in an orthotopic breast cancer. The highly stable SFNs with a low critical association concentration provide a safe and spacious harbor for hydrophobic drugs. Furthermore, the stimulus-responsive evaluation and in vitro drug release study show that the SFNs can balance intracellular dissociation for drug release and extracellular stability in the blood circulation. Additionally, the tumor penetration capacity has been dramatically enhanced in 3D multicellular spheroids, effectively affecting cells far from the periphery. This can be ascribed to the coadministration of iRGD having tumor-penetrating ability and fluorocarbon chains having good cell membrane permeability. The combination of SFNs and iRGD is a viable approach to assist drugs' effective accumulation in primary and metastasized tumor sites, significantly inhibiting the breast tumor growth and curbing lung and liver metastases in an orthotopic-tumor-bearing mouse model. Taken together, this pH-sensitive fluorinated nanosystem having excellent stability and tumor accumulation and penetration properties paves the way to combat cancer.

Solution properties of hydrophobically modified polyacrylamides and their potential use for polymer flooding application

We tested nine hydrophobically modified polyacrylamides with molecular weights situated between 1.58 and 0.89×106g/mol for enhanced oil recovery applications. Their solution properties were investigated in the distilled water, brine solution, formation water and sea water. Their critical association concentrations were determined from the relationship between their concentrations and the corresponding apparent viscosities (ηapp) at 30°C at shear rate 6s−1. They were between 0.4 and 0.5g/dl. The brine solutions of 0.5g/dl of HM-PAMs were investigated at different conditions regarding their apparent viscosities. Such conditions were mono and divalent cations, temperature ranging from 30 to 90°C, the shear rate ranging from 6 to 30s−1 and the aging time for 45days. The surface and interfacial tensions for the HM-PAMs were measured for concentration range from 0.01 to 1g/dl brine solutions at 30°C and their emulsification efficiencies were investigated for 7days. The discrepancy in the properties and efficiencies of the tested copolymers was discussed in the light of their chemical structure.

Superamphiphilic nanocontainers based on the resorcinarene – Cationic surfactant system: Synergetic self-assembling behavior

Self-organization in the mixed system based on water-soluble aminomethylated calix[4]arene with sulfonatoethyl groups at the lower rim and classical cationic surfactant cetyltrimethylammonium bromide has been studied by the methods of tensiometry, conductometry, spectrophotometry, dynamic and electrophoretic light scattering. The values of the critical association concentration, the size and zeta potential values, and the solubilization capacity of mixed aggregates toward the hydrophobic probe (Sudan I) were determined.

Physicochemical and biological characterizations of Pxt peptides from amphibian (Xenopus tropicalis) skin.

Pxt peptides (Pxt-1 through Pxt-12) have been isolated from amphibian, Xenopus tropicalis Pxt-related peptides (Pxt-2, Pxt-5, Pxt-12, reverse Pxt-2, reverse Pxt-5 and reverse Pxt-12) with significant foaming properties were further characterized. In the physicochemical experiments, all Pxt-related peptides formed significant amphiphilic α-helices in 50% 2,2,2-trifluoroethanol by circular dichroism measurements. Among Pxt-related peptides, both Pxt-5 and reverse Pxt-5 were the most effective in reducing their surface tensions. Moreover, Pxt-2, Pxt-5 and reverse Pxt-5 produced constant surface tensions above their critical association concentrations, suggesting the micelle-like assemblies. In the biological experiments, Pxt-5 possessed the most potent hemolytic activity, while reverse Pxt-5 exhibited the most remarkable gene expression of interleukin 8 and heme oxygenase 1 and the most potent cytotoxicity in HaCaT cells. In contrast, Pxt-12 and reverse Pxt-12 were much weaker in antimicrobial assays for Gram-negative bacteria, Gram-positive bacteria and yeasts, as well as in hemolytic, cell viability and cytotoxicity assays in HaCaT cells. All Pxt-related peptides exhibited about 20-50% of the total cellular histamine release at 10(-5) M, as well as mastoparan and melittin in mast cells. Real-time polymerase chain reaction analysis confirmed the gene expressions of Pxt-5 in testis and Pxt-12 in muscle, in addition to skin, while Pxt-2 was only in skin.

Influence of RNA Strand Rigidity on Polyion Complex Formation with Block Catiomers.

Polyion complexes (b-PICs) are prepared by mixing single- or double-stranded oligo RNA (aniomer) with poly(ethylene glycol)-b-poly(L-lysine) (PEG-PLL) (block catiomer) to clarify the effect of aniomer chain rigidity on association behaviors at varying concentrations. Here, a 21-mer single-stranded RNA (ssRNA) (persistence length: 1.0 nm) and a 21-mer double-stranded RNA (small interfering RNA, siRNA) (persistence length: 62 nm) are compared. Both oligo RNAs form a minimal charge-neutralized ionomer pair with a single PEG-PLL chain, termed unit b-PIC (uPIC), at low concentrations (<≈ 0.01 mg mL(-1)). Above the critical association concentration (≈ 0.01 mg mL(-1)), ssRNA b-PICs form secondary associates, PIC micelles, with sizes up to 30-70 nm, while no such multimolecular assembly is observed for siRNA b-PICs. The entropy gain associated with the formation of a segregated PIC phase in the multimolecular PIC micelles may not be large enough for rigid siRNA strands to compensate with appreciably high steric repulsion derived from PEG chains. Chain rigidity appears to be a critical parameter in polyion complex association.

Amphiphilic core cross-linked star polymers as key building blocks of the hydrogels with hydrophobic domains for drug delivery

Event Abstract Back to Event Amphiphilic core cross-linked star polymers as key building blocks of the hydrogels with hydrophobic domains for drug delivery Dunyin Gu1, Katharina Ladewig1*, Molly Klimak1*, David Haylock2, Keith M. Mclean2, Andrea J. O'Connor1 and Greg G. Qiao1 1 The University of Melbourne, Department of Chemical and Biomolecular Engineering, Australia 2 Commonwealth Scientific and Industrial Research Organisation, Manufacturing Flagship, Materials Science and Engineering, Australia Introduction: Core cross-linked star (CCS) polymers represent an intriguing platform in the application of drug delivery. CCS polymers as drug carriers are more robust to environmental variations, compared with the self-assembled micelles or vesicles, which tend to disassemble below their critical association concentration or under external stimuli, followed by an undesired burst release of drugs[1],[2]. Also, the ease of designing the size or functionality of arms and cores separately makes CCS polymers more attractive than other types of unimolecular containers[3]. Like many other molecular carriers, however, the limited circulation period of CCS polymers in body would decrease the duration of drug action. In order to overcome this constraint, CCS polymers can be built into hydrogel to form a stable drug-delivery implant. Materials and Methods: In this work, CCS polymers were obtained by using ring-opening polymerization (ROP) in two steps, with firstly poly(ethylene glycol)-poly(ε-caprolactone) (PEG-PCL) copolymers being formed as macroinitiators (MIs) and then these MIs being cross linked by [4, 4'-bioxepane]-7, 7'-dione (BOD) (Fig1)[4]. Various characterization tools, such as NMR, GPC, DLS, TEM, UV-Vis spectroscopy, flow cytometry and CLSM, have been adopted to investigate the structures, drug loading and release properties (pirarubicin and doxorubicin used as model hydrophobic drugs), cytotoxicity and cellular uptake of the resulting CCS polymers. Furthermore, the functionalized PEG arm was used to introduce the reactive end groups in the outer layer of the CCS, allowing for the formation of hydrogels in the presence of certain cross-linkers (Fig2). Results and Discussion: A range of CCS polymers were made with different hydrophilic/hydrophobic balance by tuning the ratio of PEG to CL and BOD blocks. These star polymers are soluble in both organic solvents and water and exist in a unimolecular state, as characterized by DLS and TEM, which provides the opportunity to easily stabilise hydrophobic drugs in aqueous environment without the need for lengthy encapsulation techniques. Their drug loading capacity is heavily influenced by the hydrophobicity and core size. The in vitro drug release study illustrated high stability of CCS-drug complex at neutral pH and a faster release profile under acidic conditions due to the degradation of pH-sensitive PCL segments. The CCS polymers also demonstrated very low toxicity, with cell viability remaining above 80% even up to high polymer concentrations. CLSM and flow cytometry analyses indicated highly efficient cellular uptake. The hydrogels based on the PEG-PCL-BOD CCS polymers feature the uniform distribution of hydrophobic domains as the hydrophobic drug depots. The swelling, mechanical and drug loading properties of the hydrogels are largely determined by the variations in hydrophobic content of the embedded CCS polymers. Conclusions: A library of well-defined amphiphilic PEG-PCL-BOD CCS polymers was prepared through facile ROP. They have large loading capacities for hydrophobic drugs, with the CCS-drug complex displaying high stability at neutral pH and a faster release under acidic condition. The unimolecular drug containers are bio-compatible and can be internalised by cells with high efficiency. The functionalized CCS polymers could become key building blocks of the hydrogels with hydrophobic domains as drug-delivery implants for cancer therapy. The authors acknowledge the Australian Research Council under the Future and Super Science Fellowship Schemes (FT110100411, G.G.Q.; FS110200025, G.G.Q. & K.L.).; D.G. thanks The University of Melbourne for the provision of MIRS.

Interaction of Sodium Hyaluronate with a Biocompatible Cationic Surfactant from Lysine: A Binding Study.

Mixtures of natural and biodegradable surfactants and ionic polysaccharides have attracted considerable research interest in recent years because they prosper as antimicrobial materials for medical applications. In the present work, interactions between the lysine-derived biocompatible cationic surfactant N(ε)-myristoyl-lysine methyl ester, abbreviated as MKM, and the sodium salt of hyaluronic acid (NaHA) are investigated in aqueous media by potentiometric titrations using the surfactant-sensitive electrode and pyrene-based fluorescence spectroscopy. The critical micelle concentration in pure surfactant solutions and the critical association concentration in the presence of NaHA are determined based on their dependence on the added electrolyte (NaCl) concentration. The equilibrium between the protonated (charged) and deprotonated (neutral) forms of MKM is proposed to explain the anomalous binding isotherms observed in the presence of the polyelectrolyte. The explanation is supported by theoretical model calculations of the mixed-micelle equilibrium and the competitive binding of the two MKM forms to the surface of the electrode membrane. It is suggested that the presence of even small amounts of the deprotonated form can strongly influence the measured electrode response. Such ionic-nonionic surfactant mixtures are a special case of mixed surfactant systems where the amount of the nonionic component cannot be varied independently as was the case for some of the earlier studies.

Amphiphilic graft copolymers: Effect of graft chain length and content on colloid gel

A series of amphiphilic graft copolymers were synthesized by varying the number of graft chains and graft chain lengths. The polarity of the hydrophobic graft chain on the copolymers was varied their solution properties. The glass transition temperature of the copolymers was in the low-temperature region, because of the amorphous nature of poly (trimethylene carbonate) (PTMC). The surface morphology of the lyophilized colloid gel had a bundle structure, which was derived from the combination of poly(N-hydroxyethylacrylamide)( poly(HEAA)) and PTMC. The solution properties were evaluated using dynamic light scattering and fluorescence measurements. The particle size of the graft copolymers was about 30-300 nm. The graft copolymers with a higher number of repeating units attributed to the TMC (trimethylene carbonate) component and with a lower macromonomer ratio showed high thermal stability. The critical association concentration was estimated to be between <TEX>$2.2{\times}10^{-3}$</TEX> and <TEX>$8.9{\times}10^{-2}mg/mL$</TEX>, using the pyrene-based fluorescence probe technique. These results showed that the hydrophobic chain of the graft copolymer having a long PTMC segment had a low polarity, dependent on the number of repeating units of TMC and the macromonomer composition ratio. These results demonstrated that a higher number of repeating units of TMC, with a lower macromonomer composition, was preferable for molecular encapsulation.

불화계 양친매성 폴리아크릴아마이드의 합성과 용액거동

A series of hydrophobically associating fluorinated amphiphilic polyacrylamide copolymers with remarkably high heat resistance and salt tolerance were synthesized by free radical micellar copolymerization, using acrylamide (AM) and sodium 2-acrylamido-tetradecane sulfonate (<TEX>$AMC_{14}S$</TEX>) as amphiphilic monomers, and 2-(perfluorooctyl) ethyl acrylate (PFHEA) as hydrophobic monomer. The structure of the terpolymer was characterized by FTIR, <TEX>$^1H$</TEX> NMR and <TEX>$^{19}F$</TEX> NMR. The solution properties of the terpolymers were investigated in details, and the results showed that the terpolymer solution had strong intermolecular hydrophobic association as the concentration exceeded the critical association concentration 1.5 g/L. The terpolymer solution possessed high surface activity, viscoelasticity, excellent heat resistance, salt tolerance and shearing resistance. The viscosity retention rate of copolymer solution was as high as 59.9% under the condition of fresh wastewater, <TEX>$85^{\circ}C$</TEX> and a 60-days aging test.

Self-assembly properties of hydrophobically associating perfluorinated polyacrylamide in dilute and semi-dilute solutions

Hydrophobically associating perfluorinated polyacrylamide (HACFP) is a kind of novel cationic polyacrylamide prepared with acrylamide (AM), methacryloxyethyl trimethylammonium chloride (DMC) and 2-(perfluorohexyl)ethyl acrylate (FHA) through radical micellar polymerization. Macroscopic and microscopic self-assembly associative properties in solutions of HACFP as well as the effects of salt, temperature and shearing on the associative behavior were studied via viscosimetry, rheology, fluorescence spectroscopy (FS) and dynamic light scattering (DLS). Results showed that the critical association concentration (CAC) was ~0.24 wt.%, as determined via apparent viscometry and FS. The mixed hydrophobic macro-domains, which can be indicated by a change in I1/I3 FS values, and their associating behavior had apparent effects on the apparent average aggregate size (d*) observed by DLS. Also, incorporation of FHA endowed polyacrylamide with strong salt, heat and shearing resistance because of the intra- and inter-molecular hydrophobically associating aggregates which lead to a dynamic physical cross-linking network in its structure. The maximum apparent viscosity occurred when the polarity of the solution was enhanced in salt solution and the polymer coils were expanded with increased temperature.