Prevention Strategy of Cement Slurry Sedimentation under

Article pubs.acs.org/JPCC

Cite This: J. Phys. Chem. C 2019, 123, 18573−18584

Prevention Strategy of Cement Slurry Sedimentation under High Temperature. Part 1: A Polymer with Continuous ThermoThickening Behavior from 48 to 148 °C Xin Chen,†,§ Chengwen Wang,*,†,‡ Yanji Wang,† Huan Wang,† and Ruihe Wang†,‡ †

School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China Key Laboratory of Unconventional Oil & Gas Development, China University of Petroleum (East China), Qingdao 266580, China § School of Mining and Petroleum Engineering, Faculty of Engineering, University of Alberta, Edmonton T6G 1H9, Canada Downloaded via BUFFALO STATE on August 5, 2019 at 15:48:33 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

‡

ABSTRACT: Traditional thermoresponsive polymers with amphiphilicity exhibit acute thermo-thickening behaviors through phase transition and cannot be used as stabilizer to prevent high-viscosity liquid from viscosity reduction versus increasing temperature. Therefore, this study aims to develop a watersoluble polymer that has both thickening ability and continuous thermothickening ability in a wide temperature range. Inspired by the researches about hydrophobically associating polymers, a novel thermo-thickening polymer with strong hydrophobicity (HTP) has been synthesized, which consists of acrylamide (AM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and a hydrophobic monomer with surfactant character (SHM). HTP has good thermal stability and moderate resistance to the salt and alkali. In particular, HTP exhibits a continuous thermo-thickening behavior from 48 to 148 °C and can mitigate the consistency reduction of cement slurry under high temperatures. A series of experimental results (including environmental scanning electron microscope, gel permeation chromatography, differential scanning calorimeter, and pyrene fluorescence probe) indicate that the microstructure changes of HTP molecules in solution determine the thickening and thermo-thickening behaviors of HTP. The thickening behavior of HTP is due to the generation of spatial molecular networks in solution. The formed networks become more tangled and larger along with increasing HTP concentration resulting in a higher viscosity of solution. Under higher temperature, the tangled HTP molecular chains may stretch and fabricate much larger and denser networks causing the thermo-thickening behavior of HTP. It is hoped that the thermo-thickening polymer presented in this paper can be applied in various fields.

1. INTRODUCTION With the depletion of oil and gas stored in shallow reservoirs, an enormous amount of research effort has gone into the exploration and development of deep oil and gas resources. However, the high temperature in the deep bottom hole may cause several challenges on well cementing.1−4 The particles within cement slurry are prone to sedimentation under high temperature resulting in slurry instability when cementing deep well sections. This seriously threatens the quality of well cementing and the safety of oil and gas production.5−7 Based on the Stokes’ law,8 the settling velocity of small spheres in fluid can be presented as eq 1. γp − γf v = Kgr 2 μ (1)

viscosity variation of cement slurry (or other liquids with high viscosity) versus temperature can be presented as curve (a) in Figure 1 and the viscosity of slurry continuously decreases with increasing temperature. Thus, preventing slurry viscosity from reduction versus temperature through adding chemicals should be a practicable and effective tactic to improve slurry stability. In other words, we need to invent a novel additive that can achieve the thermo-thickening behavior like the curve (b) in Figure 1 to stabilize slurry. Note that the cement slurry is one of the liquid mixtures with high viscosity. So only when the chemicals exhibit both strong thickening behavior (i.e., significantly improving the solution viscosity with relatively low dose) and thermothickening behavior (i.e., the thickening behavior becoming stronger with increasing temperature) in water (with low viscosity), can they be expected to prevent the viscosity reduction and help to realize the constant viscosity of cement slurry versus temperature shown as the curve (c) in Figure 1.

where v is the settling velocity, K is the shape coefficient (for 1 example, K = 18 for the small spheres), γ is the specific gravity (the subscripts p and f mean particle and fluid, respectively), g is the acceleration of gravity, r is the radius of the particle, and μ is the dynamic viscosity of the fluid. Clearly, the viscosity reduction may increase the settling velocity of cement particles resulting in the slurry segregation and sedimentation.3 The © 2019 American Chemical Society

Received: June 2, 2019 Revised: July 5, 2019 Published: July 9, 2019 18573

DOI: 10.1021/acs.jpcc.9b05255 J. Phys. Chem. C 2019, 123, 18573−18584

Article

The Journal of Physical Chemistry C

suspensions for drilling fluids and cement slurries, but those suspensions did not perform thermoresponsive behaviors and their application temperatures were not very high (below 120 °C).33,34 However, most available literature introduced the effect of polymer concentration, surfactant, shear stress, salinity and pH on the rheological properties of hydrophobically associating polymer solutions.35−38 Recently, few paper focused on the viscosity variation of hydrophobically associating polymer solution versus temperature, although in 1998, McCormick et al. hinted that some hydrophobically associating polymers containing long carbon chains might exhibit thermothickening ability.39 Nevertheless, Hourdet et al. stated that the polymers with strong hydrophobicity could perform a thermothinning behavior in solution.40 Therefore, in order to clear the controversy, it is significant and interesting to verify if the polymers with strong hydrophobicity can yield a thermothickening behavior. In this paper, based on previous researches about amphiphilic thermoresponsive polymers and hydrophobically associating polymers, we synthesize a thermo-thickening polymer with strong hydrophobicity (HTP). Thermo-thickening mechanism of HTP would be determined by a series of analysis experiments. Admittedly, with lots of studies have been carried out on the amphiphilic thermoresponsive polymers, the characterizing measurement and experimental process have been fixed.9,10 For example, the molecular structure, thermal stability and hydrophobicity of polymer are usually determined through infrared spectroscopy (IR), thermogravimetric and differential thermal analysis (TG-DTA) and pyrene fluorescence probe (PFP), respectively, which have also been adopted in this study. However, the strong hydrophobicity of HTP leads to failure analyses through some traditional experimental methods. Therefore, we modified the analytical approaches of some traditional experiments. For instance, gel permeation chromatography (GPC) always helps to determine and compare the weight of macromolecules.41 However, in this study, the molecular weight of HTP obtained from GPC was not reliable. Howbeit, GPC could be used to contrast the hydrodynamic volume of microstructure formed by HTP molecules.42 Besides, differential scanning calorimeter (DSC) would be used for heat flow detection to indicate the solubility change of polymer with increasing temperature in this study rather than determining the phase transition temperature.43,44 More significantly, the intermolecular interaction plays a pivotal role on the thickening behavior of polymer.45,46 In this study, we directly observed the microstructure of HTP molecules in solution through environmental scanning electron microscope (ESEM). In summary, this study provides a synthesized strategy for thermo-thickening polymer. This thermo-thickening polymer has the potential to prevent the viscosity reduction of cement slurry or other high-viscosity liquid and its solution viscosity can continuously grow with increasing temperature. The thermothickening mechanism of this polymer displayed in this paper may also lay the foundation for the future development of smart polymers.

Figure 1. Schematic of viscosity variation trend of four liquids versus temperature.

When it comes to the thermo-thickening materials, the poly(N-isopropylacrylamide) (PNIPAM) and poly(ethylene glycol) (PEG) are deemed as two of the most widely used thermoresponsive polymers.9 Some researchers have also presented good literature overviews about the PNIPAM-based polymers, PEG-based polymers, and their homologues.10−12 It is believed that their amphiphilicity (both hydrophilic and hydrophobic groups within the polymer molecules) brings about the thermo-thickening behavior.13 At the temperature below lower critical solution temperature (LCST), the polymer molecules easily dissolve in the aqueous phase under the impact of hydrophilic groups and the solution exhibits a low viscosity. With increasing temperature and approaching to LCST, hydrophobic groups come into playing leading effect to reduce the solubility of polymer and form intermolecular hydrophobic microdomains, resulting in the viscosity increase.14,15 After over LCST, the polymer precipitates significantly and the intermolecular networks collapse simultaneously, causing the solution viscosity slump.16 The viscosity variation of amphiphilic polymer solution versus temperature has been presented as the curve (d) in Figure 1. This acute thermoresponsive model induced by phase transition may be favored by biotechnology, pharmacy and textile industry.9,17−23 However, obviously, this viscosity variation model cannot contribute to compensate for the consecutive viscosity reduction of cement slurry. Moreover, the bottomhole temperatures of oil and gas wells are typically more than 100 °C, while the LCSTs of PEG-based polymers and PNIPAM-based polymers are usually below 80 °C.24,25 Although the phase-transition temperature can be improved through polymerizing with hydrophilic monomer (such as N,Ndimethylacrylamide, PDMA), the thickening ability of polymer will also become pale.26−28 On the contrary, polymerizing with hydrophobic monomer leads to the hydrophobically associating polymer with stronger thickening ability and the associated molecular chains within polymers impel the network generation under lower temperatures.29 Hence, we raise a question: Can improving the hydrophobicity of synthesized polymer induce a thermo-thickening behavior? Previously, in the petroleum and chemical industry, because of the high viscosity of solution, the water-soluble hydrophobically associating polymers have been emphasized on the application in enhanced oil recovery,30 which has been summarized by some researchers.31,32 Moreover, the hydrophobically associating polymers have ever been used as

2. SYNTHESIS AND CHARACTERIZATION OF THERMO-THICKENING POLYMER 2.1. Synthesis of Thermo-Thickening Polymer. In view of low cost and simple process, the novel thermo-thickening polymer would better be directly copolymerized in deionized water induced by a redox system, i.e., sodium bisulfite (NaHSO3) and ammonium peroxydisulfate ((NH4)2S2O8). 18574


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Through a series of optimization experiments, the formula of HTP has been determined and presented in Table 1. For

This convenient synthesis method is also conducive to future industrial production. Wever et al. stated that the synthesized AM-g-NIPAM copolymer distributed by random monomers exhibited a stronger thickening capability than that of copolymer distributed by block monomers.47 Thus, the monomers used for HTP synthesis would also be premixed well in the solution before adding initiator to ensure the random monomer distribution. Aiming to be used as an additive for cement slurry, the synthesized polymer should exhibit a good water-solubility. Previously, hydrophobically associating polymers are usually copolymerized in organic solvent or through surfactant micelle because of poor water-solubility of hydrophobic monomers.48−50 However, those polymerization methods would not produce polymers with good water-solubility and have high production costs.49,51 In this study, we would adopt a hydrophobic monomer with surfactant character (SHM) according to Peiffer’ theory.51 The typical SHM was prepared through the reaction between chloropropene and N,N-dimethyl long-chain alkylamine and the reaction process is shown as eq 2,

Table 1. Composition of Synthesized Polymer polymer name thermo-thickening polymer with strong hydrophobicity NIPAM-based copolymer AM-c-AMPS copolymer

code name

weight ratio of monomers

HTP

AM:AMPS:SHM = 6:3:1

NBP AAP

AM:AMPS:NIPAM = 2:1:3 AM:AMPS = 2:1

comparison purposes, the NIPAM-based copolymer (NBP) and AM-c-AMPS copolymer (AAP) have also been prepared through similar synthesis process of HTP. Table 2 lists the chemical materials used for polymer synthesis and following experiments. Table 2. List of Experimental Materials Adopted in This Study chemical

where n may be 11, 13, 15, or 17. In this study, the N,N-dimethyl octadecylamine was used for SHM synthesis (i.e., n = 17). The obtained SHM is well soluble in water and easily copolymerizes with other monomers. Acrylamide (AM) is one of the most used monomers due to its good thermal stability and high polymerization activity.52 Therefore, AM has been adopted as the major monomer in HTP. 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) has also been used for copolymerization to further improve the thermal stability of HTP.53 Equation 3 displays the polymerization process of HTP, where X, Y, and Z stand for the reacted molar ratio of AM, AMPS, and SHM.

purity

manufacturer

2-acrylamido-2-methyl propanesulfonic acid acrylamide

AR

anhydrous alcohol

CP

sodium hydroxide

CP

sodium bisulfite

CP

sodium chloride

CP

ammonium peroxydisulfate

CP

N-isopropylacrylamide chloropropene N,N-dimethyl dodecylamine

CP CP AR

pyrene acetone

CP

Guangdong Wengjiang Chemical Reagent Corp. Sinopharm Chemical Reagent Corp. Sinopharm Chemical Reagent Corp. Sinopharm Chemical Reagent Corp. Sinopharm Chemical Reagent Corp. Sinopharm Chemical Reagent Corp. Sinopharm Chemical Reagent Corp. Aladdin Chemical Reagent Corp. Aladdin Chemical Reagent Corp. Guangdong Wengjiang Chemical Reagent Corp. Aladdin Chemical Reagent Corp. Sinopharm Chemical Reagent Corp house-made

hydrophobic monomers with surfactant character deionized water

CP

house-made

For the convenience of application and analysis, the obtained polymer gel was needed to be dried and purified. The gel was first prepared as a diluted solution with a weight concentration of about 10%. Then the polymer solution was tiled on a plate and dried in vacuum at 80 °C for 3 days. Next the polymer solid was ground to fine powder through an agate mortar and rinsed with acetone and then dried in vacuum and ground again. The drying, grinding and rinsing process would be repeated by three times. The polymer powder after drying and purification was used for solution preparation and analysis experiments. 2.2. Verification for Molecular Structure. The infrared spectroscopy (IR) and nuclear magnetic resonance-hydrogen spectrum (1H NMR) are the two major experimental methods to characterize the molecular structure of polymer.54 However, the synthesized HTP is hardly dissolved in heavy water and other common deuterium reagents. Therefore, only IR (conducted by NEXUS 470 Fourier transformation infrared spectrometer, produced by Nicolet Instrument Technologies Inc., America) has been adopted to verify if the molecular

A representative synthesis procedure is presented here. The used monomers are dissolved in deionized water with a weight concentration of 20%, respectively. Then the monomer solutions are mixed well and the pH of mixed solution is also adjusted to 8−9 by 10% sodium hydroxide (NaOH) solution. After that, this solution is poured into a flask and stirred by an electric mixer at a constant speed of 100 r/min in a water bath with 50 °C. Until the temperature of the reaction solution also achieves to 50 °C, the initiator solution is slowly added into the reaction solution. The initiator solution is prepared by NaHSO3 and (NH4)2S2O8 with the weight concentrations of 1% and 1.6%, respectively. The effective weight ratio between the total used monomers and the total initiators is about 1000:6. The final weight concentration of all of the monomers in the reaction solution is about 15%. Stop stirring when the viscosity of the reaction solution starts to obviously increase (about 20 min after adding initiator solution). After cured under 50 °C for 10 h, a milky white polymer gel is obtained. 18575


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The Journal of Physical Chemistry C structure of synthesized polymer is consistent with the original designed one. The IR spectra of HTP, AAP, and SHM are presented as Figure 2 and the typical absorption peaks have been marked.

Figure 3. Viscosity variations of 0.4% HTP solution, 4% NBP solution, and 4% AAP solution versus temperature (20−90 °C).

viscosities of those solutions are significantly lower than those of HTP solution at all temperatures. This proves that the polymer with strong hydrophobicity is able to thicken solution intensely. Besides, the viscosity of AAP solution slightly decreases versus temperature while there is a sharp peak in the viscosity variation of NBP solution. This abrupt viscosity variation indicates the thermal-responsive behavior of NBP, which has been conformed by previous researches about NIPAM-based polymer.9 It is noteworthy that the viscosity of HTP solution gradually increases after 50 °C. Therefore, we can claim that our synthesis method of thermo-thickening polymer is practicable and feasible, i.e., the hydrophobic monomer can give the polymer with the thermo-thickening behavior. Notably, HTP exhibits both the thickening behavior and the thermo-thickening behavior. We discuss those performances with details and try to provide some explanations in section 3 and 4, respectively. 2.4. Thermal Stability. As mentioned before, the temperatures of deep oil and gas reservoirs are often above 100 °C or even exceed 150 °C.3 Therefore, it is a prerequisite for the polymer used in bottom hole to withstand high temperatures. The thermal stability of HTP has been determined by TG209F3 Tarsus thermo-microbalance (produced by NETZSCH Instruments Co., German) and the results are showed in Figure 4. The testing temperature range was 25−600 °C and the heating rate was about 5 °C/min.

Figure 2. IR spectra of HTP, AAP, and SHM synthesized in this study.

According to Figure 2, the IR spectrum of SHM shows the absorption peaks of ammonium radical at the wavenumber of 3420 cm−1, methyl and methylene at near 2944 and 2826 cm−1, and carbon−carbon double bond at 1620 cm−1. Besides, the absorption peaks of methyl, methylene and carbon−nitrogen bonds are superimposed at the wavenumber of 1452 cm−1. The long carbon chain generates the characteristic peak at 720 cm−1. From the IR spectrum of AAP, the wide absorption peak at 3120−3660 cm−1 and the high-intensity peak at 1675 cm−1 represent the amide. The absorption peaks of sulfonate appear at 1188, 1040, and 605 cm−1. Apparently, the IR spectrum of HTP is similar to that of AAP, where the absorption peaks of amide and sulfonates can be observed. However, the absorption peaks of methyl and methylene at 2944 and 1452 cm−1 in HTP exhibit stronger intensity than those in AAP, which indicate that there are more methyl and methylene within HTP. In addition, the characteristic peak at 720 cm−1 illustrates that HTP contains long carbon chain of SHM. Above results manifest that the synthesized HTP has both absorption peaks of AAP and SHM and is a terpolymer of AM, AMPS and SHM. Therefore, we can conclude that HTP has been successfully synthesized. 2.3. Verification for Thickening and Thermo-Thickening Behavior. In order to verify whether our synthesized polymer can yield a thermal-thickening behavior, in this section, we would compare the viscosity of HTP solution against NBP and AAP solutions. The polymer solutions of HTP, NBP and AAP were prepared with concentrations of 0.4%, 4% and 4%, respectively. Those polymers have been dissolved and stirred in deionized water for more than 48 h under 20 °C to ensure the complete dissolution. Then, we used a ZNN-D6 cylinder viscometer (produced by Qingdao Haitongda Instruments, China) to determine the apparent viscosities (under the rotational speed of 300 s−1) of those polymer solutions under different temperatures (20−90 °C). Note that this section was only a verification test, so we recorded the viscosities of solutions per 10 °C just to make clear the trends of viscosity variations. The experimental results are summarized in Figure 3. As seen in Figure 3, although the concentration of NBP and AAP solutions is one order higher than that of HTP solution, the

Figure 4. TG-DTA spectrum of synthesized HTP (25−600 °C). 18576


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The Journal of Physical Chemistry C The TG-DTA spectrum of HTP can be divided into four stages. The first stage is from 25 to 228 °C, where the residual mass slowly declines while thermoelectric potential gradually grows versus temperature. The mass loss during this stage is about 7.2%. This is mainly due to the evaporation of free water which was absorbed by sulfonate and hydrophobic groups in HTP. In the second stage, the residual mass decreases obviously from 228 to 332 °C and the mass loss is about 26.1%. In the same time, there is an wide valley on the curve of thermoelectric potential. Those indicate the thermal decomposition of oxygencontaining groups such as amide and sulfonate in HTP. With increasing temperature, the reduction of residual mass aggravates from 332 to 435 °C, where the mass loss is about 39.2%. This sharping reduction states that the polymer backbone begins to break down. After over 435 °C, the residual mass of HTP becomes stable and the final residual mass is about about 27.5%, indicating the thorough decomposition of HTP. In general, the molecule of HTP can keep intact below 228 °C and HTP has excellent thermal stability. 2.5. Salt and Alkaline Tolerances. Salts affect not only the thermoresponsive behavior of amphiphilic polymer but also the thickening ability of hydrophobically associating polymer.13,55 Moreover, the alkaline environment of cement slurry can also influence the properties of polymer.38 Hence, we investigated the effects of salt (NaCl) and alkali (NaOH) on the viscosity of 0.4% HTP solution under different temperatures and the results are displayed in Figure 5. The additions of NaCl and NaOH were based on the criteria of salinity and pH, respectively, shown in Table 3. According to Figure 5a, the viscosity of 0.4% HTP solution reduces with increasing NaCl addition. When the concentration of NaCl achieves 3% (i.e., saline water), the 0.4% HTP solution cannot exhibit the thermo-thickening behavior and keep low viscosity under different temperatures. Similarly, shown in Figure 5b, the viscosity of HTP solution decreases after adding NaOH. As the NaOH concentration is less than 1% (i.e., pH ≤ 13.4), the 0.4% HTP solution has relative high viscosity under lower temperatures and exhibits a distinct thermo-thickening behavior. The pH of common cement slurry is 9−13, so HTP is suitable for the alkalescent circumstance of cement slurry. On the whole, the synthesized HTP has a moderate resistance to the salt and alkali. This is because the sulfonate within AMPS improve not only the thermal stability of synthesized polymer but also the tolerance to salts.53,56

Figure 5. Effect of NaCl and NaOH on the viscosity of 0.4% HTP solution: (a) with NaCl concentration of 0%, 0.05%, 1%, and 3%; (b) with NaOH concentration of 0%, 0.01%, 0.1%, 1%, and 4%.

Table 3. Relationship between NaCl Concentration and Salinity and Relationship between NaOH Concentration and pH

3. THICKENING PERFORMANCE AND MECHANISM OF HTP The cement slurry is a tricky mixture containing kinds of additives and exhibiting high viscosity, so a good thickening ability of HTP is beneficial to the slurry stability. If the thickening ability of HTP was weak (i.e., a low viscosity of HTP solution under room temperature), the viscosity increment caused by HTP might be unable to compensate the viscosity reduction of cement slurry with increasing temperature or set off a radical change of slurry viscosity. In this section, we would test the thickening behavior of HTP with different concentrations in solutions and try to explain its thickening mechanism through ESEM and GPC tests. 3.1. Thickening Performance of HTP. HTP solutions were prepared with the concentrations of 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, and 0.6%, respectively. Then their thickening performances were determined through the experimental

NaCl concentration (%)

salinity (g/kg)

salinity levels

NaOH concentration (%)

pH

0.05

0.5

fresh water

0.01 0.1

11.4 12.4

1

10

brackish water 1

13.4

3

30

saline water 4

14

process presented in section 2.3 and the results are shown in Figure 6. As seen in Figure 6, the viscosities (under different temperatures) of HTP solutions rise with the increasing HTP concentrations. Both 0.1% and 0.05% HTP solutions have very low viscosities (below 35 mPa s) under different temperatures. Nevertheless, the viscosities of 0.2% HTP solution has increased to about 90 mPa·s. It is remarkable that the viscosity of 0.3% HTP solution will gradually increase after temperature above 50 °C. This shows that only with relatively high concentration can 18577


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thickening performance and those networks become more dense with increasing HTP concentration. 3.3. Hydrodynamic Volume of Polymer Structure. Proverbially, GPC is conducted to determine the weights of macromolecules and the molecular weights obtained from GPC are the indirect ones calculated based on the hydrodynamic volumes of polymers.41 Generally, some organic solvents are adopted as matrices to ensure the individual distribution of molecules in tested solution rather than swelling and crosslinked molecular groups.57,58 However, the HTP synthesized in this study is also hardly dissolved in tetrahydrofuran which is one of the most used organic solvents for GPC. Hence, the aqueous solutions of HTP were adopted for GPC tests. The measured molecular weights can refer to the hydrodynamic volumes of networks formed by HTP molecules rather than the real ones. In this study, we adopted GPC-20A gel permeation chromatography system with SB-806 M HQ chromatographic column (produced by Shimadzu Co., Japan) to test the polymer samples. The testing temperature and driving pressure were 40 °C and 1.7 MPa, respectively. Polyacrylamide was used as the standard sample to calculate the molecular weights. Table 4 lists the number-average and weight-average molecular weights of HTP determined through 0.2%, 0.4%, and 0.6% solutions and those of AAP (for comparison propose) determined through 0.5% and 1% solutions. In Table 4, the molecular weights of AAP determined through 0.5% and 1% solutions are approximate. By comparison, HTP solutions with different concentrations may produce a very wide range of molecular weights. Besides, the molecular weights of HTP are much larger than those of AAP. Although the SHM used for synthesized HTP contains a long carbon chain, its fraction in HTP is too small to improve molecular weight so greatly. Based on the observation in section 3.2, the molecular chains of HTP associate together to generate a spatial network. Therefore, the molecular weight of HTP determined by GPC may be the total weight of the spatial network rather than a single molecule. Because the synthesis processes of AAP and HTP are similar, the real number-average molecular weight of HTP should be also about millions like AAP. In addition, the increasing molecular weights indicate that the hydrodynamic volumes of spatial networks become larger with increasing HTP concentrations. Thus, with higher concentrations, the formed spatial networks are not only denser but also larger, which make the polymer solutions thickener. Based on the analyses of GPC and ESEM, we can conclude the thickening mechanism of HTP and draw a simple schematic shown in Figure 8. HTP exhibits an effective thickening behavior in solution through forming spatial network. With increasing HTP concentration, the formed spatial networks become more denser and larger resulting in a higher viscosity of HTP solution.

Figure 6. Viscosity variations of HTP solutions with different concentrations (0.05%−0.5%) versus temperature (20−90 °C).

HTP perform a thermo-thickening behavior. Certainly, 0.3% is still a low dosage, which may bring good economic benefits. In addition, HTP has been predissolved for a long time (48 h) before the test, so this thermo-thickening behavior can be considered as a characteristic of HTP rather than caused by the incomplete dissolution. The viscosities of 0.5% HTP solution after 70 °C becomes too high and exceeds the testing range of the rotational viscometer. Besides, the viscosities of 0.3% and 0.4% HTP solutions seem to maintain the growth trend after 90 °C. This indicates that HTP has a thermo-thickening potential under high temperatures (>100 °C). Therefore, this study would also determine the thermo-thickening performance of HTP with higher concentrations under higher temperatures through advanced rotational rheometer and the results are shown in Section 4.1. 3.2. Micromorphology of HTP in Solution. As mentioned before, the morphology of polymer in solution plays a critical role in the thermoresponsive and thickening behavior of polymer.45 In order to find out why HTP can produce the intense thickening behavior, we would directly observe the micromorphology of HTP in solution (with concentrations of 0.2% and 0.6%, respectively) through Quanta 250 FEG environmental scanning electron microscope (produced by Field Electron and Ion (FEI) Company, U.S.A.). 1% AAP solution was also observed for comparison propose. The representative photos are shown in Figure 7. All samples have been deep frozen and dehydrated under −10 °C through refrigeration and vacuum equipment attached to this ESEM before taking photos. As shown in Figure 7a,b, with a low concentration of 0.2%, HTP can form a spatial network in solution through associated molecular chains. This network contributes to the high viscosity of HTP solution. In Figure 7c,d, with a higher HTP concentration (0.6%), the spatial network becomes more denser than that of 0.2% HTP solution and the meshes within the network become smaller at the same time. Besides, some molecular chains have intertwined and tied together. Predictably, this tangled molecular chains may untie under high temperatures and cause a thermo-thickening performance. By contrast, in Figure 7e,f, even with a higher concentration (1%), AAP cannot form a network in solution and its molecular chains present a strip distribution and weak association. Thus, AAP exhibits a poor ability to thicken solution. Altogether, HTP can form molecular networks in solution resulting in good

4. THERMO-THICKENING PERFORMANCE AND MECHANISM OF HTP The experimental results in section 2.2 and 3.1 have stated that HTP shows a thermo-thickening performance after achieving a certain concentration. In this section, we would display the thermo-thickening behavior of HTP under higher temperatures. Then based on the endothermic and hydrophobic variations of HTP solutions versus temperature, we would provide a available interpretation for that thermo-thickening phenomenon. 4.1. Thermo-Thickening Performance of HTP in Deionized Water. The ZNN-D6 cylinder viscometer used in section 2.2 and 3.1 can only test the viscosity of HTP solution 18578


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Figure 7. Representative ESEM photos of different polymer solution: (a) and (b) taken from 0.2% HTP solution; (c) and (d) taken from 0.6% HTP solution; (e) and (f) taken from 1% AAP solution.

below 100 °C. Therefore, we would adopt HAAKE RheoStress 1 rotational rheometer (produced by Thermo Fisher Scientific Co., German) to determine the thermo-thickening behavior of HTP solutions (with concentration of 0.2%, 0.4%, and 0.6%) under higher temperatures. The shear rate was 430 s−1 and the testing temperature range was 25−185 °C with the heating rate of 2 °C/min. Eight data points would be recorded per minute. The obtained curves are shown in Figure 9 after being smoothed.

As seen in Figure 9, HTP solutions with higher concentrations have higher viscosities (under different temperatures) like the results presented in Section 3.1. The viscosities of those HTP solutions would rapidly decrease after 148 °C. According to the experimental results in Section 2.4, the molecular structure of HTP should remain intact below 228 °C. Thus, the possible reason for this violent viscosity reduction is the destruction of networks formed by HTP molecules rather than the decomposition of HTP itself. In addition, the viscosity of 0.2% HTP solution decreases slightly versus temperature before 148 18579


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drilling engineering.59 Therefore, the HTP exhibits continuous thermo-thickening behavior from 48 to 148 °C, which is in prospect of used as additives to the treatment fluids for drilling deep well. Moreover, in order to verify the thermo-thickening behavior of HTP in cement slurry, the consistency variations of hightemperature cement slurry system containing silica flour versus temperature have been determined. The compositions of hightemperature cement slurry system and the testing results are displayed in Table 5 and Figure 10, respectively. The high-

Table 4. Obtained GPC Molecular Weights of HTP Determined through 0.2%, 0.4%, and 0.6% Solutions and AAP Determined through 0.5% and 1% Solutions polymer name HTP

AAP

concentration

number-average molecular weight, Mn

weight-average molecular weight, Mw

0.2% 0.4% 0.6% 0.5% 1%

7.11 × 107 1.15 × 109 8.67 × 109 1.53 × 106 1.62 × 106

1.34 × 108 2.74 × 109 1.60 × 1010 1.94 × 106 2.19 × 106

Figure 8. Schematic of thickening mechanism of HTP.

Figure 10. Effect of HTP on consistency of high-temperature cement slurry system containing silica flour.

pressure cement consistometer DFC-0712B (produced by Shenyang Jinke Petroleum Instruments Company) with the testing temperature range 30−150 °C was adopted. As shown in Figure 10, without HTP, the consistency of hightemperature cement slurry containing silica flour gradually decreases versus temperature. The consistency has declined by 39.8% during test (shown in Table 5). This indicates that the cement slurry tends to be thin under high temperatures, which may be conducive to the settlement of cement particles. After adding 0.025% HTP, the consistency of high-temperature cement slurry remains relatively constant during temperature rising. This proves the thermo-thickening behavior of HTP in the cement slurry, which mitigates the consistency reduction. With a higher addition of HTP (0.05%), the consistency of hightemperature cement slurry increases versus temperature. Thus the thermo-thickening behavior of HTP in the cement slurry also becomes stronger with increasing addition just like that in the deionized water. It is noteworthy that the consistency of high-temperature cement slurry containing HTP does not drop at 150 °C, although the viscosity of HTP solution would rapidly decrease after 148 °C. There is a wider temperature range of HTP exhibiting thermo-thickening behavior in the cement slurry.

Figure 9. Viscosity variations of 0.2%, 0.4%, and 0.6% HTP solutions versus temperature (25−185 °C).

°C. Meanwhile, the viscosity of 0.4% HTP solution moderately increases from 48 to 148 °C while that of 0.6% HTP solution displays a dramatic rise versus temperature. The viscosity ratios between 48 and 148 °C of 0.4% HTP solutions is 1.55 and that of 0.6% HTP solutions is 1.91. The LCST of available thermoresponsive polymer with amphiphilicity (typically including PNIPAM-based polymers and PEG-based polymers) is usually 30−80 °C;24,25 thus, the traditional thermoresponsive polymers cannot work as thickener over 100 °C. In general, the formation temperature gradient is about 2.5−3 °C/100 m and the depth of formation temperature to achieve 150 °C is 4500− 6000m, which can be classified as the depth of deep well in

Table 5. Composition of High-Temperature Cement Slurry System Containing Silica Flour and the Consistency Variation during Test cement

silica flour (%)

water/solid (%)

HTP (%)

filtrate reducer (%)

high-temperature retarders (%)

consistency at 30 °C (Bc)

consistency at 150 °C (Bc)

consistency variation (%)

class-G class-G class-G

35 35 35

0.38 0.38 0.38

0 0.025 0.05

5 5 5

0.3 0.3 0.3

34.7 31.7 32.0

20.9 32.6 37.1

−39.8 2.8 15.9

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5 × 10−6 mol/L in HTP solution. The obtained fluorescence spectra are displayed in Figure 12.

4.2. Endothermic Variation of HTP versus Temperature. The phase transition of polymer in solution (i.e., from dissolved to undissolved) causes a thermal change. From this aspect, DSC is usually adopted to determine the LCST of amphiphilic thermoresponsive polymers.44 In this study, we also tested the endothermic variation of HTP solution (with the concentration of 0.2% and 0.6%, respectively) versus temperature through Q20 differential scanning calorimeter (produced by TA Instruments, U.S.A.). The testing temperature range was 30−90 °C with the heating rate of about 5 °C/min and the filling gas was nitrogen. The obtained DSC thermograms are displayed in Figure 11.

Figure 12. Fluorescence spectra of 0.6% HTP solution under 25, 50, and 90 °C.

The excitation wavelength was 334 nm in this test and two typical vibronic peaks of the emission spectra (i.e., I1 and I3) of pyrene located at near 372.5 and 383 nm, respectively. The intensity ratio I1/I3 usually refers to the degree of hydrophobicity (nonpolarity) of aqueous phase. The I1/I3 value of pure water is near 1.813. A low value of I1/I3 indicates hydrophobic microenvironment where pyrene can be soluble, while a high value indicates strong hydrophilicity. The I1/I3 intensity ratios of 0.6% HTP solution under different temperatures have been calculated and presented in Table 6.

Figure 11. DSC thermograms of 0.2% and 0.6% HTP solutions (testing temperature range: 30−90 °C).

In Figure 11, the DSC thermogram of 0.2% HTP solution is very smooth. This indicates that there is no obvious phase transition in 0.2% HTP solution during heating process. By contrast, there is a abrupt turning point at 47.8 °C in 0.6% HTP solution. This turning point matches the temperature that the viscosity of 0.6% HTP solution starts to increase in Figure 9. Commonly, when a phase transition occurred in amphiphilic thermoresponsive polymer solution, there should be a sharp valley (or peak) in DSC thermogram.26,44,60 However, the slope change of DSC thermogram after 47.8 °C indicates a continuous microdomain variation causing the viscosity increment rather than sudden phase transition. Based on the observation in section 3.2, with a higher concentration, the HTP molecular chains tend to intertwine and tie together besides forming spatial networks in solution. Therefore, it is conceivable that the stretching chains and further dissolution of HTP molecules resulting in the endothermic variation. Meanwhile, this also contributes to denser and larger networks and the increasing viscosity of HTP solution with temperature. 4.3. Hydrophobic Variation of HTP versus Temperature. It is necessary to determine the hydrophobic variation of HTP solution versus temperature because of the strong hydrophobicity of HTP. As far as available references are concerned, pyrene fluorescence probe (PFP) is considered as one of the most effective ways to characterize hydrophobic interactions.13,61,62 Accordingly, in this study, steady state fluorescence of 0.6% HTP solution (containing pyrene) was recorded under different temperatures (25, 50, and 90 °C) by a FLS980 Spectrometer (produced by Edinburgh Instruments, U.K.) equipped with a water bath. Pyrene in alcohol solution (1 × 10−4 mol/L) was used as a probe with a final concentration of

Table 6. Intensity ratio I1/I3 of 0.6% HTP solution under 25, 50, and 90 °C temperature (°C)

I1

I3

I1/I3

25 50 90

1117834.75 704347.75 434173.47

752873.50 477845.22 330367.75

1.485 1.474 1.314

As shown in Table 6, the intensity ratios I1/I3 of 0.6% HTP solution are lower than 1.8. This manifests the strong hydrophobicity of HTP. In addition, there is few variation of I1/I3 from 25 to 50 °C while a obvious reduction of I1/I3 when the temperature rises to 90 °C. This indicates that the hydrophobicity of 0.6% HTP solution does not change much during 25−50 °C but increases significantly during 50−90 °C. This hydrophobicity increment provides a firm support for the assumption about the further dissolution of HTP molecules after 48 °C proposed in section 4.2. A denser and larger network induced by the stretching molecular chains leads to the improved hydrophobicity as well as the thermo-thickening behavior of 0.6% HTP solution. Admittedly, there are lack of available experimental methods to directly observe the micromorphology of HTP molecules in solution under high temperatures. But combining with the experimental results obtained from ESEM, DSC and PFP, we can conjecture the themo-thickening mechanism of HTP and provide the schematic as Figure 13. Under relatively low temperature, some molecular chains of HTP have tied together resulting in tangled networks. With increasing temperature, the entwined chains may stretch in the solution and fabricate denser 18581


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Figure 13. Schematic of thermo-thickening mechanism of HTP.

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and larger networks, which contribute to the thermo-thickening behavior. After achieving a certain temperature, the viscosity slump of HTP solution was due to the spatial networks disintegration. Generally, the thermo-thickening ability of HTP is the outcome of the solubility increment and stretching molecules, which differs from that of amphiphilic thermoresponsive polymers yielded by phase transition.13−16

AUTHOR INFORMATION

Corresponding Author

*Phone: (86)15264259168. E-mail: [email protected]. ORCID

Xin Chen: 0000-0001-7467-3812 Notes

The authors declare no competing financial interest.

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5. CONCLUSIONS This study provides a synthesis method for polymer with continuous thermo-thickening behavior in a wide temperature range and reveals its thermo-thickening mechanism. The major experimental findings can be summarized as follows:

ACKNOWLEDGMENTS The authors greatly acknowledge the financial support from the National Natural Science Foundation of China (No. U1762212 and 51704325), project No. ZR2017MEE056 supported by Shandong Provincial Natural Science Foundation, and Changjiang Scholar Program of Chinese Ministry of Education (IRT_14R58). X.C. also greatly acknowledges the Ph.D. Scholarship from the China Scholarship Council (CSC; No. 201806450029) for the financial support.

• A novel thermo-thickening polymer with strong hydrophobicity (HTP) has been synthesized, which consists of AM, AMPS and a hydrophobic monomers with surfactant character (SHM). • HTP has excellent thermal stability and its molecular can maintains intact below 228 °C. • HTP can effectively thicken the solution and its thickening and thermo-thickening behaviors become both more violent with increasing concentration. • HTP molecular chains can form spatial networks in solution and the networks become more tangled, denser and larger with increasing HTP concentration resulting in a higher solution viscosity. • In contrast to the abrupt viscosity variation of amphiphilic thermoresponsive polymer in a narrow temperature range, HTP exhibits a continuous thermo-thickening behavior from 48 to 148 °C. • HTP has a moderate resistance to the salt and alkali and can mitigate the consistency reduction of cement slurry under high temperatures. • With increasing temperature, the tangled HTP molecular chains can stretch and fabricate further denser and larger networks in solution causing the thermo-thickening behavior. After achieving 148 °C, the networks formed by HTP molecular chains start to disintegrate causing the viscosity slump. The thermo-thickening mechanism of HTP is the gradual changes of solubility and microstructure, which differs from that of amphiphilic thermoresponsive polymers yielded by phase transition.

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REFERENCES

(1) Shaheen, M.; Schulz, J.; Haddad, G. S.; Helou, H. Cementing under Extreme Conditions of High Pressure and High Temperature. In SPE/IADC Middle East Drilling Technology Conference; United Arab Emirates, Abu Dhabi, 8−10 Nov 1999. (2) Bullard, J. W.; Jennings, H. M.; Livingston, R. A.; Nonat, A.; Scherer, G. W.; Schweitzer, J. S.; Scrivener, K. L.; Thoma, J. J. Mechanisms of Cement Hydration. Cem. Concr. Res. 2011, 41, 1208− 1223. (3) Nelson, E. B.; Guillot, D. Well Cementing, 2nd ed.; Schlumberger: Amsterdam, The Netherlands, 2006. (4) Xiong, M.; Liew, J. Y. R. Mechanical Behaviour of Ultra-high Strength Concrete at Elevated Temperatures and Fire Resistance of Ultra-High Strength Concrete Filled Steel Tubes. Mater. Des. 2016, 104, 414−427. (5) Matson, R. P.; Rogers, M. J.; Boncan, V. C. G.; Gandy, R. G. The Effects of Temperature, Pressure, and Angle of Deviation on Free Water and Cement Slurry Stability. In 66th Annual Technical Conference and Exhibition of the; Society of Petroleum Engineers, Dallas, TX, 1991. (6) Rosquoet, F.; Alexis, A.; Khelidj, A.; Phelipot, A. Experimental Study of Cement Grout: Rheological Behavior and Sedimentation. Cem. Concr. Res. 2003, 33, 713−722. (7) Peng, Y.; Jacobsen, S. Influence of Water/Cement Ratio, Admixtures and Filler on Sedimentation and Bleeding of Cement Paste. Cem. Concr. Res. 2013, 54, 133−142. (8) Song, Z.; Wu, T.; Xu, F.; Li, R. A Simple Formula for Predicting Settling Velocity of Sediment Particles. Water Sci. Eng. 2008, 1, 37−43. (9) Dimitrov, I.; Trzebicka, B.; Muller, A. H. E.; Dworak, A.; Tsvetanov, C. B. Thermosensitive Water-Soluble Copolymers with Doubly Responsive Reversibly Interacting Entities. Prog. Polym. Sci. 2007, 32, 1275−1343. (10) Liu, R.; Fraylich, M.; Saunders, B. R. Thermoresponsive Copolymers: From Fundamental Studies to Applications. Colloid Polym. Sci. 2009, 287, 627−643.

We hope that HTP will not only be adopted as a stabilizer for cement slurry but also used in other fields. The thermothickening mechanism provided in this paper may shed light into the further research on the development of thermo-thickening polymer. 18582


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Enhanced Oil Recovery-Article Review. Egyptian J. Petrol. 2017, 26, 757−762. (33) Xie, B.; Liu, X. Thermo-Thickening Behavior of LCST-Based Copolymer Viscosifier for Water-Based Drilling Fluids. J. Pet. Sci. Eng. 2017, 154, 244−251. (34) Lu, H.; Xie, C.; Gao, Y.; Li, L.; Zhu, H. Cement Slurries with Rheological Properties Unaffected by Temperature. SPE Drill. Completion 2016, 30, 316−321. (35) Lu, H.; Liu, Y.; Wang, B.; Zheng, C.; Huang, Z. Self-Assembling Transition Behavior of a Hydrophobic Associative Polymer Based on Counterion and pH Effects. Colloids Surf., A 2016, 490, 1−8. (36) Sarsenbekuly, B.; Kang, W.; Fan, H.; Yang, H.; Dai, C.; Zhao, B.; Aidarova, S. B. Study of Salt Tolerance and Temperature Resistance of a Hydrophobically Modified Polyacrylamide Based Novel Functional Polymer for EOR. Colloid Surface A: Physicochem. Eng. Aspects 2017, 514, 91−97. (37) Alves, L.; Lindman, B.; Klotz, B.; Bottcher, A.; Haake, H. M.; Antunes, F. E. On the Rheology of Mixed Systems of Hydrophobically Modified Polyacrylate Microgels and Surfactants: Role of the Surfactant Architecture. J. Colloid Interface Sci. 2018, 513, 489−496. (38) Feng, Y.; Billon, L.; Grassl, B.; Bastiat, G.; Borisov, O.; Francois, J. Hydrophobically Associating Polyacrylamides and Their Partially Hydrolyzed Derivatives Prepared by Post-Modification. 2. Properties of Non-Hydrolyzed Polymers in Pure Water and Brine. Polymer 2005, 46, 9283−9295. (39) McCormick, C. L.; Nonaka, T.; Johnson, C. B. Water-Soluble Copolymers: 27. Synthesis and Aqueous Solution Behaviour of Associative Acrylamide/N-Alkylacrylamide Copolymers. Polymer 1988, 29, 731−739. (40) Hourdet, D.; Gadgil, J.; Podhajecka, K.; Badiger, M. V.; Brulet, A.; Wadgaonkar, P. P. Thermoreversible Behavior of Associating Polymer Solutions: Thermothinning versus Thermothickening. Macromolecules 2005, 38, 8512−8521. (41) Maley, L. E. Application of Gel Permeation Chromatography to High and Low Molecular Weight Polymers. J. Polym. Sci., Part C: Polym. Symp. 1965, 8, 253−268. (42) Porath, J.; Flodin, P. Gel Filtration: A Method for Desalting and Group Separation. Nature 1959, 183, 1657−1659. (43) Nyamweya, N.; Hoag, S. W. Assessment of Polymer-Polymer Interactions in Blends of HPMC and Film Forming Polymers by Modulated Temperature Differential Scanning Calorimetry. Pharm. Res. 2000, 17, 625−631. (44) Boutris, C.; Chatzi, E. G.; Kiparissides, C. Characterization of the LCST Behaviour of Aqueous Poly(N-Isopropylacrylamide) Solutions by Thermal and Cloud Point Techniques. Polymer 1997, 38, 2567− 2570. (45) Annable, T.; Buscall, R.; Ettelaie, R.; Whittlestone, D. The Rheology of Solutions of Associating Polymers: Comparison of Experimental Behavior with Transient Network Theory. J. Rheol. 1993, 37, 695−726. (46) Xu, D.; Hawk, J. L.; Loveless, D. M.; Jeon, S. L.; Craig, S. L. Mechanism of Shear Thickening in Reversibly Cross-Linked Supramolecular Polymer Networks. Macromolecules 2010, 43, 3556−3565. (47) Wever, D. A. Z.; Riemsma, E.; Picchioni, F.; Broekhuis, A. A. Comb-Like Thermoresponsive Polymeric Materials: Synthesis and Effect of Macromolecular Structure on Solution Properties. Polymer 2013, 54, 5456−5466. (48) Volpert, E.; Selb, J.; Candau, F. Associating Behaviour of Polyacrylamides Hydrophobically Modified with Dihexylacrylamide. Polymer 1998, 39, 1025−1033. (49) Candau, F.; Biggs, S.; Hill, A.; Selb, J. Synthesis, Structure and Properties of Hydrophobically Associating Polymers. Prog. Org. Coat. 1994, 24, 11−19. (50) Valint, P. L.; Bock, J. Synthesis and Characterization of Hydrophobically Associating Block Polymers. Macromolecules 1988, 21, 175−179. (51) Peiffer, D. G. Hydrophobically Associating Polymers and Their Interactions with Rod-Like Micelles. Polymer 1990, 31, 2353−2360.

(11) Badi, N. Non-Linear PEG-Based Thermoresponsive Polymer Systems. Prog. Polym. Sci. 2017, 66, 54−79. (12) Roy, D.; Brooks, W. L. A.; Sumerlin, B. S. New Directions in Thermoresponsive Polymers. Chem. Soc. Rev. 2013, 42, 7214−7243. (13) Durand, A.; Hourdet, D. Thermoassociative Graft Copolymers Based on Poly(N-Isopropylacrylamide): Effect of Added Co-Solutes on the Rheological Behaviour. Polymer 2000, 41, 545−557. (14) Durand, A.; Hourdet, D. Synthesis and Thermoassociative Properties in Aqueous Solution of Graft Copolymers Containing Poly(N-Isopropylacrylamide) Side Chains. Polymer 1999, 40, 4941− 4951. (15) Hourdet, D.; L’Alloret, F.; Audebert, R. Synthesis of Thermoassociative Copolymers. Polymer 1997, 38, 2535−2547. (16) Zhang, X.; Zhou, L.; Zhang, X.; Dai, H. Synthesis and Solution Properties of Temperature-Sensitive Copolymers Based on NIPAM. J. Appl. Polym. Sci. 2010, 116, 1099−1105. (17) Boularas, M.; Radji, S.; Gombart, E.; Tranchant, J. F.; Alard, V.; Billon, L. Functional Film by Trigger-Free Self-Assembly of Adhesive Soft Microgels at Skin Temperature. Mater. Des. 2018, 147, 19−27. (18) Ahn, S.; Ahn, S. W.; Song, S. C. Thermosensitive Amphiphilic Polyphosphazenes and Their Interaction with Ionic Surfactants. Colloids Surf., A 2008, 330, 184−192. (19) Islam, M. R.; Serpe, M. J. Poly(N-Isopropylacrylamide) Microgel-Based Thin Film Actuators for Humidity Sensing. RSC Adv. 2014, 4, 31937−31940. (20) Jiang, S.; Liu, F.; Lerch, A.; Ionov, L.; Agarwal, S. Unusual and Superfast Temperature-Triggered Actuators. Adv. Mater. 2015, 27, 4865−4870. (21) Li, Y.; Zhao, D.; Li, Y.; Liu, Y.; Duan, Q.; Kakuchi, T. Synthesis of Water-Soluble and Thermoresponsive Phthalocyanine Ended Block Copolymers as Potential Photosensitizer. Dyes Pigm. 2017, 142, 88−99. (22) Guo, X.; Li, D.; Yang, G.; Shi, C.; Tang, Z.; Wang, J.; Zhou, S. Thermo-Triggered Drug Release from Actively Targeting Polymer Micelles. ACS Appl. Mater. Interfaces 2014, 6, 8549−8559. (23) Kakwere, H.; Leal, M. P.; Materia, M. E.; Curcio, A.; Guardia, P.; Niculaes, D.; Marotta, R.; Falqui, A.; Pellegrino, T. Functionalization of Strongly Interacting Magnetic Nanocubes with (Thermo)Responsive Coating and Their Application in Hyperthermia and Heat-Triggered Drug Delivery. ACS Appl. Mater. Interfaces 2015, 7, 10132−10145. (24) Sabhapondit, A.; Borthakur, A.; Haque, I. Characterization of Acrylamide Polymers for Enhanced Oil Recovery. J. Appl. Polym. Sci. 2003, 87, 1869−1878. (25) Panayiotoua, M.; Garret-Flaudy, F.; Freitag, R. Co-Nonsolvency Effects in the Thermoprecipitation of Oligomeric Polyacrylamides from Hydro-Organic Solutions. Polymer 2004, 45, 3055−3061. (26) Fischer, F.; Zufferey, D.; Tahoces, R. Lower Critical Solution Temperature in Superheated Water: The Highest in the Poly(N,NDialkylacrylamide) Series. Polym. Int. 2011, 60, 1259−1262. (27) Xu, J.; Jiang, X.; Liu, S. Synthesis of Low-Polydispersity Poly(NEthylmethylacrylamide) by Controlled Radical Polymerizations and Their Thermal Phase Transition Behavior. J. Polym. Sci., Part A: Polym. Chem. 2008, 46, 60−69. (28) Szilagyi, A.; Zrinyi, M. Temperature Induced Phase Transition of Interpenetrating Polymer Networks Composed of Poly(Vinyl Alcohol) and Copolymers of N-Isopropylacrylamide with Acrylamide or 2Acrylamido-2-Methylpropyl-Sulfonic Acid. Polymer 2005, 46, 10011− 10016. (29) Xie, B.; Qiu, Z.; Huang, W.; Cao, J.; Zhong, H. Characterization and Aqueous Solution Behavior of Novel Thermo-associating Polymers. J. Macromol. Sci., Part A: Pure Appl.Chem. 2013, 50, 230− 237. (30) Wever, D. A. Z.; Picchioni, F.; Broekhuis, A. A. Polymers for Enhanced Oil Recovery: A Paradigm for Structure-Property Relationship in Aqueous Solution. Prog. Polym. Sci. 2011, 36, 1558−1628. (31) Taylor, K. C.; Nasr-El-Din, H. A. Water-Soluble Hydrophobically Associating Polymers for Improved Oil Recovery: A Literature Review. J. Pet. Sci. Eng. 1998, 19, 265−280. (32) El-hoshoudy, A. N.; Desouky, S. E. M.; Elkady, M. Y. Hydrophobically Associated Polymers for Wettability Alteration and 18583


Article

The Journal of Physical Chemistry C (52) Myagchenkov, V. A.; Kurenkov, V. F. Applications of Acrylamide Polymers and Copolymers: A Review. Polym.-Plast. Technol. Eng. 1991, 30, 109−135. (53) Bock, J.; Valint, P. L.; Pace, S. J. Enhanced Oil Recovery with Hydrophobically Associating Polymers Containing Sulfonate Functionality. U.S. Pat. 1987, 4702319. (54) Yang, J. C.; Jablonsky, M. J.; Mays, J. W. NMR and FT-IR Studies of Sulfonated Styrene-Based Homopolymers and Copolymers. Polymer 2002, 43, 5125−5132. (55) Zhang, Y.; Furyk, S.; Bergbreiter, D. E.; Cremer, P. S. Specific Ion Effects on the Water Solubility of Macromolecules: PNIPAM and the Hofmeister Series. J. Am. Chem. Soc. 2005, 127, 14505−14510. (56) Liu, X.; Wang, Y.; Lu, Z.; Chen, Q.; Feng, Y. Effect of Inorganic Salts on Viscosifying Behavior of a Thermoassociative Water-Soluble Terpolymer Based on 2-Acrylamido-methylpropane Sulfonic Acid. J. Appl. Polym. Sci. 2012, 125, 4041−4048. (57) Johnson, J. F.; Porter, R. S.; Cantow, M. J. R. Gel Permeation Chromatography with Organic Solvents. J. Macromol. Sci., Polym. Rev. 1966, 1, 393−434. (58) Drott, E. E.; Mendelson, R. A. Determination of Polymer Branching with Gel-Permeation Chromatography. I. Theory. J. Polym. Sci. Part A 1970, 8, 1361−1371. (59) Zhao, Y. S.; Feng, Z. J.; Xi, B. P.; Yang, D.; Liang, W. G.; Wan, Z. J. Limit of crustal drilling depth. J. Rock Mech. Geotech. Eng. 2017, 9, 989−992. (60) Chuang, W. J.; Chiu, W. Y. Thermo-Responsive Nanofibers Prepared from Poly (N-Isopropylacrylamide-Co-N-Methylol Acrylamide). Polymer 2012, 53, 2829−2838. (61) Zhao, C. L.; Winnik, M. A. Fluorescence Probe Techniques Used To Study Micelle Formation in Water-Soluble Block Copolymers. Langmuir 1990, 6, 514−516. (62) Skvarla, J.; Zednik, J.; Slouf, M.; Pispas, S.; Stepanek, M. Poly(NIsopropyl Acrylamide)-Block-Poly(N-Butyl Acrylate) Thermoresponsive Amphiphilic Copolymers: Synthesis, Characterization and SelfAssembly Behavior in Aqueous Solutions. Eur. Polym. J. 2014, 61, 124− 132.

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