Thermo-thickening Behavior Research Articles

Thermo-thickening/amphoteric polymer nanocomposite incorporating vinyl-functionalized nano-silica as a viscosifier for high-salt and ultra-high temperature water-based drilling fluids

In the relentless extraction of oil and gas from deeper reservoirs, the harsh geological conditions pose significant rheological challenges for conventional polymer viscosifiers. Hence, the spotlight has turned to the unique potential of thermo-thickening polymers to enhance drilling fluid performance. In this study, a novel polymer nanocomposite (VMS-ATA) was designed to associate thermo-thickening responses, amphoteric characteristics, and vinyl-functionalized nano-silica (VMS) as nanofillers for the formation of a thermally stable polymer nanocomposite-bentonite hybrid system. VMS-ATA was prepared via in-situ polymerization under optimal synthetic conditions, and the unique chemical structure was analyzed using various techniques such as Fourier transform spectroscopy, proton nuclear magnetic resonance, elemental analysis, thermogravimetric analysis, X-ray spectroscopy, transmission electron microscopy, and scanning electron microscopy. The study systematically investigated the enhancement of in-situ covalent bonding characteristics of VMS on the thermo-thickening behavior of VMS-ATA, while comparing it with amine-nano-silica (AMS) incorporated in a polymer composite (AMS-CGBA). TGA analysis revealed that VMS-ATA exhibits excellent thermal stability compared to AMS-CGBA, attributed to the thermally stable VMS (370 °C) compared to AMS (355 °C). Interestingly, VMS-ATA displayed relatively stable and prolonged thermo-thickening responses (100–200 °C) owed to high thermal-induced activation responses above the lower critical solution temperature (LCST) in both salt-free and saturated salt contamination. The rheological results of VMS-ATA viscosity retention at 220 °C and 20 wt% NaCl, exceeded 60 %, which is twice that of AMS-CGBA-containing fluids. As demonstrated, VMS-ATA and AMS-CGBA exhibited similar macro-interactions with rigid imidazole and caprolactam rings, but significantly differed in their micro-interactions owed to in-situ covalent binding induced by VMS compared to hydrogen bonding in AMS. This breakthrough exhibited the potential of VMS nanofillers to effectively maintain thickening response by facilitating efficient heat distribution to minimize rapid viscosity decay and revolutionize the landscape of high-salt and high-temperature (HSHT) drilling applications.

Synthesis and characterization of chitosan-based graft copolymers with temperature-switchable and self-adaptive plugging performance for drilling in microporous formation

The increasing oil–gas explorations in microporous formations and the intensified environmental requirements necessitate the development of high-performance, environmentally friendly and sustainable plugging materials to maintain wellbore stability in drilling engineering. In this work, a series of graft copolymers of carboxymethyl chitosan-g-poly(oligo(ethylene glycol) methyl ether methacrylate-co-acrylic acid) (GCOA) is synthesized through free-radical graft-from polymerization. The oligo(ethylene glycol) methyl ether methacrylate (OEGMA) and acrylic acid (AA) can be well copolymerized in the grafts as confirmed by structural characterizations, and the incorporation of AA improves the grafting ratio and grafting efficiency. All obtained GCOAs possess the temperature-responsive aggregation behavior, which causes the formation of aggregated meso-assemblies from original nano-micelles when heating above their lower critical solution temperature (LCST), accompanied by the phase separation. Meanwhile, the presence of AA segments increases the LCST due to the resistance of enhanced polymer–polymer electrostatic repulsion to the hydrophobic attraction. By the delicate control of AA molar ratio from 0 to 50 mol%, the LCST values of GCOAs can be adjusted from 90 °C to 110 °C. Furthermore, the GCOAs are formulated as smart plugging fluids and the intelligent plugging evaluation method is established based on core flow test with continuous temperature control. The results indicate that the GCOAs can form effective plugging in both low- and median-permeability cores when temperature reaches above a switching point and the formed plugging can be partially removed after cooling, showing the temperature-switchable and self-adaptive plugging capacity as a consequence of reversible retention of GCOA aggregates and thermo-thickening behavior in pore-throat spaces. These features enable the implementation and removal of in-situ plugging in the specific temperature sections during drilling, and provide a new insight into the design of novel smart plugging materials with sustainable and recycling values.

An insight into the thermo-thickening behavior of wormlike micellar solutions based on ultra-long-chain surfactants

Generally, the solution viscosity of wormlike micelles (WLMs) assembled from common surfactants decreases upon an increase in the temperature, following the Arrhenius law. However, abnormal thermo-thickening behavior has been repeatedly observed for WLMs formed by ultra-long-chain (≥C18) surfactants. It would be useful to unravel the mechanism behind this phenomenon. Here, three C22-tailed surfactants with an erucyl tail, two of them containing carboxylate or sulfonate head groups (UC22DAB and UC22DAS) and a cationic one with an iodide counterion (UC22DAI), and two C18-tailed betaines with olemido- and stearamidopropyl hydrophobic chains (UC18DAS and C18DAS) were characterised in terms of their viscosity and viscoelastic behavior with increasing temperature to examine the roles of head groups, tail length and tail nature. Their micellar structures were elucidated at various temperatures using small angle neutron scattering (SANS), small angle neutron X-ray scattering (SAXS) and molecular dynamics simulation. It is found that the thermo-thickening behavior of ultra-long-chain surfactants is ascribed to the prolonged persistence length and increased entanglement points. When the temperature is increased, an increase in viscosity is always accompanied by a longer persistent length, thus a larger hydrodynamic volume. The iceberg structure around the hydrophobic tail of surfactants can be destroyed at high temperatures leading to the self-assembly of these surfactants. In this self-assembly process, compared to cationic surfactants, zwitterionic surfactants can form WLMs more readily due to weak electrostatic repulsions between their head groups; the longer tails give the surfactants enhanced hydrophobicity to form WLMs with a long breaking time; the cis-unsaturation and the resulting kink in the hydrophobic tails give the surfactants good solubility, which is not conducive to the formation of micelles. In brief, the zwitterionic, longer tail and saturated tail surfactants can form WLMs with a prolonged persistence length at elevated temperatures.

Design and synthesis of novel di‐ and triblock amphiphilic polyelectrolytes: Improving salt‐induced viscosity reduction of water solutions for potential application in enhanced oil recovery

AbstractIn the present study, three different block copolymers based on styrene, tert‐butyl methacrylate, and glycidyl methacrylate (GMA) were synthesized via sequential atom transfer radical polymerization. The addition of the GMA block was found to be best performed at 60°C. The polymers were then hydrolyzed and neutralized, to afford amphiphilic block copolymers, and the rheological properties of their aqueous solutions were measured, in order to investigate solution properties relevant for enhanced oil recovery, as a function of the polymer structure. It was observed that these polymers behave as thickening agents with shear thinning behavior. As expected, the polymers were sensitive to the presence of salt, as lower viscosities were recorded in saline water. However, the viscosity is less affected by high salinity, when compared to previously studied analogous diblock systems. In the best case, the viscosity only decreased by a factor of 1.8 upon salt addition whereas it decreased by a factor of 10 in previously reported non‐GMA containing polymers. Finally, thermo‐responsive behavior was found for one of the synthesized polymers. In particular, a hydrolyzed triblock poly[styrene‐b‐tert‐butyl methacrylate‐b‐glycidyl methacrylate], which synthesis is reported here for the first time, showed a thermothickening behavior, promising for the intended application in oil recovery.

Thermo-associating polymers based on cross-linked 2-acrylamido-methylpropane sulfonic acid, part B: Effect of co-solutes on solution behavior

Thermo-thickening copolymers have gained prominence in technological advancements due to its attractive properties and great potential to overcome the deficiency of viscosity of conventional copolymer upon increasing temperature and salinity. The work in this paper was devoted to examine the aqueous solution viscosity behavior of a new class thermo-thickening copolymer, poly(sodium 2-acrylamido-2-methylpropanesulfonic acid-co-N,N’-methylenebisacrylamide)-g-poly(acrylamide-co-N, N’-diethylacrylamide) denoted as CGBA in the presence of co-solutes. CGBA, which were reported in our previous work manifested notable viscosity enhancement macroscopically above the threshold temperature. However, the effect of small molecules on thermo-associative behavior was still unsettled. Based on structure/properties dependence of CGBA, this work aimed to explore the effect of small molecules and the role of molecular structure on aqueous solution viscosity behavior. The contributions of various added co-solutes such as anionic surfactant, acidic specie, monovalent and divalent salts were considered. For that purpose, three copolymers having distinctive composition of side-arms and length of side-arms were selected and their thermo-associating behaviors were followed by viscosity measurement. Results from rheological tests showed that these co-solutes induced notable modifications in the characteristic of thermo-thickening behavior. For all the co-solutes used, it was observed a strong dependence between the side-arms/water/co-solutes ternary system and the macroscopic property upon heating. Spectrofluorimetric and environmental scanning electron microscope (ESEM) tests were used to gain a deeper insight into the precise mechanism of phase transition process. Results from spectrofluorimetric experiment indicated that, only when the fraction of DEAm in CGBA was higher enough, it would appear strong abrupt macroscopic property above the threshold temperature, which could delay the offset of hydrophobic association phenomenon in the presence of anionic surfactant. Similar effect was also observed in the presence of added acidic specie. Conversely, the addition of monovalent and divalent salts showed dissimilar effects. ESEM revealed that, in comparison with monovalent salt, divalent salt favored the formation of larger and more condensed CGBA skeleton above the threshold temperature which led to an improved macroscopic response. This work demonstrates for the first time the micro-structure changes of copolymer, which was probably the main reason for the changes in magnitude of thermo-thickening effect in different divalent salt dosages.

Highly Branched Waxy Potato Starch-Based Polyelectrolyte: Controlled Synthesis and the Influence of Chain Composition on Solution Rheology

In the present work, a series of highly branched random copolymers of acrylamide (AM), sodium 2-acrylamido-2-methyl-1-propanesulfonate (SAMPS), and N-isopropylacrylamide (NIPAM) were prepared by using water-soluble waxy potato starch-based macroinitiator via aqueous Cu0-mediated living radical polymerization (25 °C). The AM/SAMPS/NIPAM ratio was varied to investigate the influence of chain composition on the aqueous rheological properties of the prepared copolymers. Rheological results indicated an optimum SAMPS intake (25 mol %) for the balanced performance of viscosity and salt resistance in saline water. The intake of NIPAM units (e.g., 25 mol %), contrary to what was expected, undermines the thickening ability of the copolymers in saline water because of hydrophobic association. In high salinity solution, thermo-thickening behavior can be observed at low shear rates (γ ≤ 3 s–1) because of the screening effect of salt on the negatively charged SAMPS units. At the high shear rate, the thermo-thickening behavior disappears because of the disruption of the NIPAM aggregates. These results pave the way toward the use of the prepared polymers as rheology modifiers in a variety of possible formulations for different applications, in particular in enhanced oil recovery.

Dynamics and Rheological Behavior of Chitosan-Grafted-Polyacrylamide in Aqueous Solution upon Heating.

In this work, the transformation of chitosan-grafted-polyacrylamide (GPAM) aggregates in aqueous solution upon heating was explored by cryo-electron microscope (cryo-TEM) and dynamic light scattering (DLS), and larger aggregates were formed in GPAM aqueous solution upon heating, which were responsible for the thermo-thickening behavior of GPAM aqueous solution during the heating process. The heating initiates a transformation from H-bonding aggregates to a large-sized cluster formed by self-assembled hydrophobic chitosan backbones. The acetic acid (HAc) concentration has a significant effect on the thermo-thickening behavior of GPAM aqueous solution; there is a critical value of the concentration (>0.005 M) for the thermo-thickening of 10 mg/mL GPAM solution. The concentration of HAc will affect the protonation degree of GPAM, and affect the strength of the electrostatic repulsion between GPAM molecular segments, which will have a significant effect on the state of the aggregates in solution. Other factors that have an influence on the thermo-thickening behavior of GPAM aqueous solution upon heating were investigated and discussed in detail, including the heating rate and shear rate.

Prevention Strategy of Cement Slurry Sedimentation under High Temperature. Part 1: A Polymer with Continuous Thermo-Thickening Behavior from 48 to 148 °C

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 v...

A thermothickening polymer as a novel flocculant for oily wastewater treatment

ABSTRACT In this work, the effectiveness of poly(acrylamide-co-N,N-diethylacrylamide-co-n-butylstyrene), designated as TTF which exhibits a thermothickening behavior, was examined as a novel flocculant for oily wastewater treatment. The effects of flocculant concentration, temperature, and electrolyte on TTF flocculation performance were examined in comparison with cationic polyacrylamide (CPAM). TTF exhibited a lower critical solution temperature (LCST) of 53°C when the monomer feed molar ratio of acrylamide/N,N′-diethyl acrylamide/n-butylstyrene: 73/26/1 was used. Moreover, increasing the concentration of NaCl and CaCl2 adversely reduced the LCST of TTF. Furthermore, treatment with TTF proved excellent performance in removing oil and suspended solid than CPAM in all conditions investigated.

Thermo thickening behavior of MPEG-b-PCL grafted Poly(acrylic acid): A molecular insight

We report on the synthesis and characterization of a new thermothickening polymer (PAA-g-(MPEG-b-PCL)) based on the grafting of a block copolymer of mono methoxy poly (ethylene glycol)–b-poly (caprolactone) (MPEG-b-PCL) onto poly (acrylic acid) (PAA). Rheological experiments reveal that aqueous solutions of PAA-g-(MPEG-b-PCL) exhibit interesting irreversible thermothickening behavior above a certain polymer concentration and critical temperature. Light scattering experiments show that increasing temperature induces hydrophobic associations and subsequent aggregation leading to gel formation which is irreversible. The mechanism of thermo thickening was examined at the molecular level by NMR methods which indicated unassembled and assembled environments of the MPEG-b-PCL grafts. On heating, interactions between the graft side chains are significantly enhanced and molecular mobility in the assembled microdomains is reduced. The stable well ordered microdomains that are formed on heating are retained on cooling thus, leading to irreversible gelation.

Thermo-Responsive Starch-g-(PAM-co-PNIPAM): Controlled Synthesis and Effect of Molecular Components on Solution Rheology.

A series of highly branched random copolymers of acrylamide (AM) and N-isopropylacrylamide (NIPAM) have been prepared from a waxy potato starch-based macroinitiator by aqueous Cu0-mediated living radical polymerization (Cu0-mediated LRP). The NIPAM intake in the copolymer was varied between 0% and 50 mol % to evaluate the influence of chain composition on the aqueous rheological properties as well as their low critical solution temperature (LCST). The viscosity of the copolymer was found to increase with the NIPAM intake and an LCST can be observed when the NIPAM content is high enough (e.g., 50 mol %). In addition, thermo-thickening behavior was observed at a low shear rate (γ ≤ 10 s−1) and higher NIPAM content was found to shift the onset of thermo-thickening behavior to a lower temperature. However, the absolute increase in viscosity values is reduced with the NIPAM intake. Besides this, an interesting significant thermo-thickening behavior was also observed on highly branched starch-g-polyacrylamide at high temperatures (>80 °C), which has not been previously reported. Rheology tests also revealed a good salt-resistant property in copolymers with low NIPAM content (e.g., <25 mol %). Considering the viscosity profile in saline as compared to that in pure water, this NIPAM intake seems to represent an optimum balance of viscosity and salt-resistance performance.

Thermo-thickening behavior and its mechanism in a chitosan-graft-polyacrylamide aqueous solution.

A novel thermo-thickening behavior of a chitosan-g-polyacrylamide (CS-g-PAM, GPAM) aqueous solution is reported for the first time in this work. The viscosity of GPAM aqueous solutions significantly increases above a critical temperature upon heating, as observed in dynamic and steady rheological experiments. Differing from the widely reported hydrophobic modified CS, GPAM was prepared by grafting hydrophilic polyacrylamide side chains onto the CS backbone, therefore the thermo-thickening behavior of the GPAM aqueous solution could not be explained by the usual thermo-thickening mechanism induced by the additional hydrophobic moiety or LCST segment. The origin of the thermo-thickening in GPAM solutions was explored using transmission electron microscopy (TEM), dynamic light scattering (DLS), and nuclear magnetic resonance (NMR) tests of the GPAM solution. A transformation from a hydrogen bonding (H-bonding) aggregate to a hydrophobic aggregate upon heating was confirmed to be responsible for the thermo-thickening. The heating initiates a transformation of large loose H-bonding aggregates into abundant small compact ones formed by self-assembled hydrophobic chitosan backbones, resulting in aggregate associations and thus flocculated aggregate networks. Some factors of the thermo-thickening were investigated and discussed in detail, including the heating history, concentration, grafting ratio, and length of the PAM side chain. Besides the influence caused by the heating history, this thermo-thickening process is influenced by kinetic factors, including the mobility of the macromolecule chains and the formation of new aggregate networks that are dependent on the number of hydrophobic clusters.

Thermoresponsive behavior of sodium alginate grafted with poly(N-isopropylacrylamide) in aqueous media

Thermoresponsive graft copolymers were synthesized. Thermally induced properties were introduced by grafting poly (N-isopropylacrylamide) (PNIPAM) side chains onto a sodium alginate backbone. The resulting graft copolymers cover a broad range in PNIPAM composition and molecular weight. Remarkable thermothickening behavior in water and 0.1 M NaCl is observed by viscometry when the temperature, concentration, weight ratio of PNIPAM side chains to backbone, and PNIPAM molecular weight are higher than certain critical values. This behavior is reversible and could have applications in oil rigs and drug delivery systems.

Thermo-thickening behavior of LCST-based copolymer viscosifier for water-based drilling fluids

Thermo-thickening polymers have gained a strong interest due to its attractive properties and had great potential for making up for the deficiency of viscosity of low-solid water-based drilling fluid at high temperature. The work in this paper was focused on studying the thermo-thickening behavior of a new class of LCST-based (Lower Critical Solution Temperature) polymeric viscosifier for water-based drilling fluid. The additives, which were obtained in our previous work, showed good temperature resistance and thermo-thickening behavior in water-based drilling fluid. However, the influence of molecular composition of copolymer on thermo-associative behavior was still unsettled. Based on structure/properties relationships of copolymers, this paper aimed to investigate the thermo-association behavior of LCST-based copolymer in drilling fluid and the role of molecular composition in thermo-assembling behavior. For that purpose, five copolymers with different NVCL content were prepared with same synthetic process. Thermo-associating behavior of LCST-based copolymer in no-solid freshwater base fluid (NSFBF) and low-solid freshwater base fluid (LSFBF) was investigated by rheometer. Results from rheological tests showed that the interesting thermo-thickening behavior was intimately related to NVCL content. Only when the NVCL content was confined at a certain range, it would appear obvious thermo-thickening phenomenon above the critical associative temperature (Tass). And Power-Law and Herschel-Bulkley model were the best fit model for rheology of polymeric fluids. In relation with macroscopic viscosity properties, the phase change process in thermo-association was monitored by Differential scanning calorimetry (DSC) and H1-NMR spectroscopy. Results from DSC indicated that polymers displayed similar endotherms process in NSFBF and LSFBF. However, compared to LSFBF, the phase transition of polymer in NSFBF showed the lower phase transition temperature (Tp) and the higher heats of transition (ΔH). H1-NMR spectroscopy showed that PVCL chains gradually became hydrophobic upon heating and the resulting hydrophobic association micro-domains led to the increase in viscosity. Furthermore, the values of Tass and Tp were compared to analyze the thermo-associative process. The polymer showed potential application as thermo-thickening viscosifier for water-based drilling fluid.

Characterization and Aqueous Solution Behavior of Novel Thermo-associating Polymers

Novel thermo-associative water-soluble polymers (PAVD) have been prepared by copolymerizing N-vinylcaprolactam (NVCL) with various amounts of sodium 2-acrylamido-2-methylpropanesulphonic acid (NaAMPS) and crosslinker divinylbenzene (DVB) using the micellar copolymerization technique. The copolymers were characterized by 1H-NMR, FT-IR, elemental analysis and GPC. The thermo-associating behavior of these copolymers was studied in aqueous solution by means of rheological experiments. It was shown that when the content of NaAMPS in copolymers was up to a certain value, the thermo-thickening behavior was clearly observed in semi-dilute aqueous solution due to the hydrophobic aggregation between VCL units. The influence of different parameters such as copolymer and salt concentrations, on the thermo-thickening behavior of the copolymers was investigated. The thermo-associative phenomenon was further analyzed by studying the relationship between the critical associative temperature and the lower critical solution temperature. More importantly, the copolymer aqueous solution exhibited excellent thermal stability at 100°C for a period of two months.

Temperature-induced thickening of sodium carboxymethylcellulose and poly(N-isopropylacrylamide) physical blends in aqueous solution

This study describes the synthesis of poly(N-isopropylacrylamide) (PNIPAM) via free radical polymerization, the preparation of physical blends containing sodium carboxymethylcellulose (CMC) and PNIPAM in aqueous solution, at total polymer concentrations of 2 and 6 g/L in different compositions, and applies rheology to investigate interactions between PNIPAM and CMC compared to pure polymers, in aqueous solution. Rheological measurements indicated thermothickening behavior for the 50 % PNIPAM–50 % CMC physical blend in aqueous solution, at 6 g/L, as viscosity rose when temperature was increased to a range of 25–40 °C. Similar thermothickening behavior was observed for the 25 % CMC–75 % PNIPAM physical blend in solution, at a total polymer concentration of 2 g/L. These results provide new information for preparing physical blends in aqueous solutions exhibiting thermothickening behavior, indicating that this behavior depends on total polymer concentration and composition of the mixture.

Thermoresponsive sodium alginate‐g‐poly(N‐isopropylacrylamide) copolymers III. Solution properties

AbstractStimuli‐responsive biocompatible and biodegradable materials can be obtained by combining polysaccharides with polymers exhibiting lower critical solution temperature (LCST) phase behavior, such as poly(N‐isopropylacrylamide) (PNIPAAm). The behavior of aqueous solutions of sodium alginate (NaAl) grafted with PNIPAAm (NaAl‐g‐PNIPAAm) copolymers as a function of composition and temperature is presented. The products obtained exhibit a remarkable thermothickening behavior in aqueous solutions if the degree of grafting, the concentration, and the temperature are higher than some critical values. The sol–gel‐phase transition temperatures have been determined. It was found that at temperatures below LCST the systems behave like a solution, whereas at temperatures above LCST, the solutions behave like a stiff gel, because of PNIPAAm segregation. This behavior is reversible and could find applications in tissue engineering and drug delivery systems. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Nanoemulsions with enhanced temperature stability using thermo-sensitive association of nonionic surfactant and amphiphilic polyelectrolytes

Aqueous mixtures containing a non-ionic surfactant (tetraethylene glycol monododecylether, C12E4), an amphiphilic polymer (poly(sodium acrylate) hydrophobically modified with azobenzene groups randomly attached along the chains, HMPA) and 0.3M NaNO3 were studied regarding the associations between macromolecules and surfactant assemblies (micelles or lamellar phases) at various temperatures (4–37°C). The effects of the thermo-induced transition of surfactant assemblies from micelles to lamellar phase on phase separation behavior were systematically investigated as a function of surfactant and polymer concentration, polymer structure (amount of grafted hydrophobic groups) and temperature. Rheological properties of polymer-rich coacervates revealed thermo-thickening behavior, in accordance with phase separation behavior. Finally, bulk phenomena were applied to design nanoemulsions with improved temperature stability taking the opportunity of strengthening interfacial layers through thermo-thickening properties.

Synthesis and characterization of thermo-sensitive graft copolymer of carboxymethyl guar and poly( N-isopropylacrylamide)

Thermo-responsive graft copolymers of carboxymethyl guar [CMG] and semitelechelic poly( N-isopropylacrylamide) [PNIPAm] were synthesized by coupling reaction between them using a water-soluble coupling agent namely, 1-(3-(dimethylamino) propyl)-3-ethyl carbodiimide hydrochloride [EDC]. The incorporation of PNIPAm into CMG was confirmed by FT-IR and NMR spectroscopy. The graft copolymers, CMG-g-PNIPAm showed enhanced viscosity as compared to the unmodified CMG in the semi-dilute regime. Due to the presence of a LCST side chains [PNIPAm], the graft copolymers exhibited thermo-responsive nature with respect to temperature which was investigated using pyrene fluorescence probe studies. Although the thermo-responsive property was observed, the thermo-thickening behavior was not seen in these polymers. The graft copolymers in the semi-dilute regime ( C p ≈ 10–20 g/L) showed viscoelastic properties and the relaxation time, τ, could be obtained from the crossover of frequency ( ω c) of storage modulus ( G′) and loss modulus ( G″) in the oscillatory experiments. The activation energy ‘ E a’ of associations was investigated using the time temperature superpsition (TTS). These thermo-responsive polymers along with the biodegradability of CMG can have potential application as industrial thickening agent.

Solution properties of thermothickening copolymers bearing hydrocarbon end‐capped oxyethylene units

AbstractNovel thermothickening copolymers composed of acrylamide and a macromer bearing hydrocarbon end‐capped oxyethylene units were synthesized. Influences of polymer concentration, salt content, shear rate, and temperature on the solution behavior were investigated. The polymer solution exhibited shear‐thickening behavior at low‐to‐moderate shear rates (&lt;50 s−1), and the shear‐thickening behavior was dependent on polymer concentration, NaCl content, and temperature. With the increase of salinity, apparent viscosity of polymer solution increased dramatically (especially at low shear rates). At higher NaCl content (&gt;20 wt %), polymer solutions became physical gel, and the apparent viscosity increased by several orders of magnitude. The polymer solutions exhibited excellent thermothickening behavior, even at the low concentration of 0.15 wt %. The results of rheological measurements showed that the storage and loss modulus were successfully fitted to a single Maxwell element at low temperature (&lt;60 °C). © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1799–1808, 2010