Associative Polymers Research Articles

Molecularly designed nonionic hydrophobic association polymers with anti-salt capacity: Enhancing drag reduction at high mineralization levels

The development of advanced anti-salt drag reduction (DR) agents is crucial for enhancing oil recovery rates, particularly in highly mineralized saline water where the network structure of polymers is prone to disruption, resulting in decreased DR. To address this problem, by carefully designing the structure of the hydrophobic association polymer, a new hydrophobic monomer called APO-10 was introduced, which successfully integrated water-soluble groups, and greatly enhanced the polymer's association properties in an aqueous solution. This ingenious approach produced a stable and robust network structure that can effectively resist the harmful effects of salt ions. PAPO-10 was synthesized through free radical polymerization and has hydrophilic EO chains that enhance its water solubility, enabling better extension of the hydrophobic long chain on the tail in solution. This facilitates the association between molecular chains, leading to the formation of a stable network structure even at low concentrations. PAPO-10 demonstrates remarkable properties, including rapid dissolution and exceptional resistance to salt. It delivers a remarkable DR of up to 78.2466 % at a concentration of 500 mg/L, dissolving within a mere 2 min in aqueous solutions. Molecular dynamics simulations confirmed that PAPO-10 exhibits strong polymer chain binding in solution, consistent with experimental results. Overall, this study provides valuable insights into the development of anti-salt polymers in slick fracturing.

Linear and Nonlinear Viscoelasticities of Dissociative and Associative Covalent Adaptable Networks: Discrepancies and Limits

Covalent adaptable networks (CANs) can be classified into dissociative (Diss-CANs) and associative (Asso-CANs) networks according to the exchange mechanism of covalent bonds. We simulate the exchange reaction by the hybrid Monte Carlo–molecular dynamics (hybrid MC/MD) algorithm, aiming to discover the connection and difference between Diss-CANs and Asso-CANs in viscoelasticity behavior. In the linear regime, a major difference originating from the cross-linking density is reflected in the pre-exponential factor τs0 of the characteristic relaxation time τs. For nonlinear rheology, Diss-CANs show a faster shear thinning behavior under steady shear, while Asso-CANs have a stronger strain hardening under the shear rate start-up. The physics behind the phenomenon results from the different chain conformations and configurations related to the exchange mechanism. Compared with Diss-CANs, the inability for sticker dissociation of Asso-CANs generates a slower relaxation under shear, leading to less chain orientation and tumbling. Meanwhile, we find that multiscale relaxation times obtained from linear viscoelasticity (LVE) can be crucial limits in nonlinear applications for associative polymers (APs). Our work strongly deepens the understanding of APs in terms of both linear and nonlinear viscoelasticities.

Transport of Associative Polymers in Low-Permeability Carbonates

Carbonate reservoirs are heterogeneous from pore scale to field scale. Waterflood in carbonate reservoirs often leaves behind a substantial amount of oil due to pore-scale and large-scale bypassing. Polymer flooding can improve sweep efficiency and oil production. Most EOR polymers cannot be transported through low-permeability (< 30 mD) rocks. Hydrophobically modified associative polymers (APs) associate with each other during passage through pore throats and give a larger flow resistance than conventional polymers (Flopaam) of the same molecular weight. The goal of this work is to investigate the transport of associative polymers in low-permeability carbonate reservoirs (less than 50 md). An associative polymer similar in molecular weight to Flopaam 3330 was investigated in this study. Polymer rheology and the effect of salinity were studied at 60 °C. Mechanical shearing and aggressive filtration were used to modify the particle size distribution in polymeric solutions and improve transport through tight cores. Single-phase polymer transport experiments were performed in outcrop Edwards Yellow and Indiana limestone cores. Mechanical shear degradation reduced the particle size and improved the transport of the associative polymer in low-permeability carbonate cores. The permeability reduction factor and the residual resistance factor were higher for the sheared AP polymers than those for the sheared Flopaam polymer. The resistance factors for the associative polymer were higher than those for Flopaam for a given shear viscosity. Coreflood experiments with AP showed the evidence of two propagation fronts: polymer concentration front and pressure gradient stabilization front due to polymer network formation and polymer adsorption. As AP polymer concentration increased, permeability reduction factor, resistance factor, residual resistance factor and polymer adsorption increased. All the coreflood experiments suggest successful polymer transport in low-permeability carbonate cores even at significantly high polymer concentrations with pre-shearing.

Studies of Hydrogen Bond between HPMC Doped CdCl2 Polymer using FTIR Technique

Hydrogen bonding between Hydroxypropyl methylcellulose (HPMC) polymeric molecules doped with Cadmium chloride (CdCl2) was investigated by using Fourier Transformation infrared technique (FTIR). The spectral variations with intensity have been measured for the binary mixtureHPMC polymerwith cadmium chloride. The complexation of metal ion with polymer was confirmed by formation of intermolecular hydrogen bonding between hydroxyl groups of HPMC and cadmium ion. The doped polymer showed enhancement in the conductivity due to increase indopant concentration. Results conforms inter molecular association ofpolymer with the metal ion

Rheology of a New Sulfonic Associative Polymer in Porous Media

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 141355, ’Rheology of a New Sulfonic Associative Polymer in Porous Media,’ by R.S. Seright, SPE, Tianguang Fan, SPE, Kathryn Wavrik, SPE, and Hao Wan, SPE, New Mexico Tech, and Nicolas Gaillard, SPE, and Cedrick Favero, SPE, SNF Floerger, prepared for the 2011 SPE International Symposium on Oilfield Chemistry, The Woodlands, Texas, 11-13 April. The paper has been peer reviewed. See SPE Reservoir Evaluation &amp; Engineering December 2011. For hydrophobic associative polymers (APs), incorporating a small fraction of hydrophobic monomer into a partially hydrolyzed polyacrylamide (HPAM) polymer can promote intermolecular associations and, thereby, enhance viscosities and resistance factors. The behavior of a new AP in porous media was investigated. Introduction In polymer or chemical floods that use polymer for mobility control, the cost effectiveness of the polymer is a major concern. Resistance factor is the effective viscosity of the polymer solution in porous media, relative to water (i.e., water mobility divided by polymer-solution mobility). HPAM and xanthan polysaccharides have been the dominant polymers used for enhanced oil recovery (EOR). If polymers that are more cost effective than these traditional EOR polymers can be identified, field applications of chemical floods could become much more widespread. For hydrophobic APs, incorporating a small fraction of hydrophobic monomer into an HPAM polymer is intended to promote intermolecular associations to enhance viscosities and resistance factors. At moderate concentrations (e.g., 0.05 to 0.5%), these polymers (with 0.1 to 7% hydrophobic monomer) can provide substantially higher viscosities than equivalent-molecular-weight polymers without hydrophobic groups. In some cases, the increase in viscosity with increasing polymer concentration is abrupt—leading to concerns about controlling the performance of the polymer during flooding operations. If small changes in concentration cause large changes in viscosity, small operational errors could accentuate injectivity problems if polymer concentrations are higher than the target and could provide insufficient mobility control if polymer concentrations are low. Another concern is the ability of APs to penetrate deep into a reservoir. Within a certain range of shear rates, the polymer becomes sufficiently extended to promote intermolecular interactions over intramolecular interactions. Polymer complexes formed by APs enhance viscosity and can provide high resistance to flow for a short distance in porous media. However, an important unresolved issue with many APs is whether the enhanced-viscosity characteristics can be propagated deep into a reservoir. Most previous studies of these polymers used short cores with no internal pressure taps to evaluate behavior in the porous media. As a result, resistance factors that appear high may actually reflect plugging. This study examined the rheology (both in a viscometer and in porous media) for a new sulfonic hydrophobic AP. This sulfonated polymer has lower hydrophobe content (and higher molecular weight) than most APs investigated for EOR previously. This sulfonated polymer exhibits viscosities that are not noticeably higher than those for the HPAM analog. It provides significantly higher resistance factors in porous media than HPAM, and the associative proper-ties allow polymer propagation through porous media.

Influence of Surfactants on Hydrophobically End-Capped Poly(ethylene oxide) Self-Assembled Aggregates Studied by SANS

The rheological properties of associative polymers (APs) are modified by the presence of surfactants, but little is known about the influence of surfactants on the structure of self-associated aggregates in aqueous media. Using small-angle neutron scattering (SANS), the structure of self-assembled aggregates of a series in concentration of telechelic poly(ethylene oxide) (M ≈ 20 000 g mol–1) end-capped by hydrocarbon or of fluorocarbon groups in the presence of a fixed amount of sodium dodecyl sulfate (SDS) or lithium perfluorooctyl sulfonate (LiFOS) is investigated. In all systems studied, surfactants and telechelic polymers form mixed aggregates. Their aggregation numbers are reduced and evolve with the concentration of each component. For example, with SDS at 8 mM, the mixed aggregates are composed of 1 AP and 15 SDS or 9 APs and 45 SDS molecules for 1 or 3 wt % of polymer, respectively. The addition of a surfactant enhances the number density of aggregates, which causes the increase of the gel viscosity.

Asymmetric End-Capped Poly(ethylene oxide). Synthesis and Rheological Behavior in Aqueous Solution

A method was developed to prepare asymmetric end-capped poly(ethylene oxide)s (PEOs), containing an alkyl group on one chain end and a perfluoroalkyl group on the other one (C18H37−PEO−C2H4−C8F17 and C18H37−PEO−C10H20−C8F17). These new telechelic associative polymers (APs) were synthesized by anionic polymerization of ethylene oxide initiated by an alkoxide (C18H37−O−K+) followed by esterification. The rheological behavior of asymmetric and analogous symmetric APs in aqueous solutions has been investigated as a function of polymer concentration (C), hydrophobic end-cap and surfactant used to homogenize the system: sodium dodecyl sulfate (SDS) or lithium perfluorooctyl sulfonate (LiFOS). A steep increase of the static viscosity η, attributed to the formation of a multiconnected network, is observed for C ≈ 1 wt %. Semidilute solutions present a Maxwellian rheological behavior with only one relaxation time τ associated with the least hydrophobic end group. The viscoelastic response is modified by the interactions between hydrophobic end groups and surfactant inside mixed aggregates.

A New Method for Acid Stimulation Without Increasing Water Production

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 103771, "A New Method for Acid Stimulation Without Increasing Water Production: Case Studies From Offshore Mexico," by G.H. Reza, Pemex, and E. Soriano, SPE, L. Eoff, SPE, and D. Dalrymple, SPE, Halliburton, prepared for the 2006 SPE International Oil Conference and Exhibition, Cancun, Mexico, 31 August-2 September. Successful acid stimulation requires a method to distribute the acid between multiple hydrocarbon zones. Because almost all producing wells contain sections of varying permeability, this can be a problem. Because acid is an aqueous fluid, it tends to enter the zones with the highest water saturation. These water zones also are often the highest-permeability zones, so acid stimulation often will result in large increases in water production. The full-length paper describes use of a new low-viscosity system that reduces formation permeability to water with little effect on hydrocarbon permeability and also diverts acid from high-permeability zones to lower-permeability zones. Introduction In matrix-acidizing treatments, the acid tends to enter the highest-permeability layers and bypass the most-damaged (lower-permeability) layers. Various placement techniques have been used in attempts to achieve uniform placement of acid across all layers. The most reliable method uses mechanical isolation devices (such as straddle packers) that allow injection into individual zones until the entire interval is treated. However, this technique often is not practical, cost-effective, or feasible. Without a packer, some type of diverting agent must be used. Typical diverting agents include ball sealers, degradable particulates, viscous fluids, and foams. Although these agents have been used successfully, all have potential disadvantages, and none address the problem of increased water production that often follows acid treatments. One method of controlling water production uses dilute polymer solutions to decrease the effective permeability to water more than to oil. These treatments are referred to as relative permeability modifiers (RPMs), disproportionate-permeability modifiers, or bullhead treatments. RPM systems are thought to perform by adsorption onto the pore walls of the formation flow paths. Previous papers have described the development of and laboratory studies of an RPM based on a hydrophobically modified, water-soluble polymer, referred to as an associative polymer (AP). This group of polymers was selected for study because their properties can be altered in ways that render them valuable for oilfield applications. Another paper has described a laboratory study of this polymer for use as an acid diverter. AP Properties The solution properties of both ionic and nonionic, water-soluble polymers are uniquely modified when hydrophobic groups are introduced into the polymer chains. The primary factor responsible for the property modification is the associative tendency between the hydrophobic groups when placed in an aqueous medium. Previous testing has shown a unique shear-thickening phenomenon for the AP used in the current work. However, the solutions used in diversion operations show very low viscosity (less than 2 cp) at surface conditions.

Using Associated Polymer Gels to Control Conformance for High Temperature and High Salinity Reservoirs

Abstract Most reservoirs in the Zhongyuan oilfield are characterized by high temperature, high salinity, and serious heterogeneity. Extensive waterflooding in the reservoir has magnified the effect of these heterogeniuties. To improve the poor conformance, a new kind of gel was developed using a water-soluble hydrophobically associating polymer (AP). Effect of the concentration of AP, crosslinker, and additives on gelation time and gel strength were studied. Thermo-stability of the gel was evaluated and results show that the gel can still retain 75 &amp;#x98; 85% of its original strength under conditions of 95 °C and salinity of 150,000 mg/l after six months. Core flooding results have illustrated that the plugging efficiency of the gel is more than 90% for selected applications. Twenty-six wells were treated using the new AP gel in the Zhongyuan oilfield in 2003. The response of treated wells and connected producers is reviewed. The average injected gel volume was 1,100 m3 each well. These treatments have resulted in approximately 6,000 m3 (5,300 tons) of incremental oil. Selection criteria for the optimum type of wells to be treated and injection procedures are summarized from the 26 applications. Introduction Gel treatment has been proved to be a cost effective method to control conformance for mature water/CO2 floods reservoirs (1–4).Traditionally, partially hydrolyzed polyacrymide (HPAM) is used to synthesize these crosslinked polymer gels. However, the traditional polymer molecular structure of these polymers tends to degrade under high salinity or hardness conditions in the injected brine, resulting in a sharp drop in viscosity of the polymer solution(5–6). Also, high molecular weight polymer tends to be irreversibly degraded by high shear rates, such as those encountered in pumps in the near wellbore region. Therefore, the application of traditional polymers of this type in high temperature and high salinity reservoirs is limited. Associating polymer (AP) is a new type of water-soluble polymer in which a small number of special hydrophobic molecular groups are directly attached to the polymer chain(5–10). In aqueous solution, the hydrophobic groups of these polymers can associate to minimize their exposure to the external fluid, resulting in a star type of large spatial network structures, as shown in Figure 1. The association results in an increase of the hydrodynamic size of polymer that increases solution viscosity. This polymer solution can have a high viscosity at a relatively low molecular weight and low concentration. This associated structure is reversible. The fluids tend to be thixotropici in nature (viscosity is reduced by increased shear rates). Most reservoirs in the Zhongyuan oilfield have high salinity and temperature and serious heterogeneity(11). The harsh reservoir conditions limit the application of traditional polymer HPAM. Therefore, AP associated polymer gel was synthesized and evaluated to control conformance in the Zhongyuan oilfield. Experiment Results Synthesis of the AP Gel AP Concentration Effect Synthesized Mazai formation water was used to prepare the polymer solution and the gel was formed at 95 °C. After three days' aging, the gel viscosity was measured at a shear rate of 12 rpm.

Probe size effects on the microrheology of associating polymer solutions.

Diffusing wave spectroscopy has been used to investigate the thermally driven displacement of colloidal particles dispersed in solutions of associating polymers (APs). The effect of varying colloidal probe size on the measured particle displacements is studied in particular. Recent theories of microrheology are examined in light of the observed effects. The associating polymer used in this research was a linear polyethylene oxide (PEO) chain (molecular weight 35 000 g/mole) with a Cl14 aliphatic group appended to each end of the PEO. Above a critical concentration, the associating polymers display linear viscoelasticity consistent with the Maxwell model. The concentration of aqueous AP solutions was varied from 0.25 to 4.0 wt. %. At low concentration of APs, the mean square displacement of the colloidal beads was indistinguishable from simple Brownian diffusion in the aqueous solvent. However, at concentrations greater than 0.5 wt. %, the mean square displacement differed from simple diffusion in a way that was found to be consistent with the Maxwell model linear viscoelasticity (LVE) of the AP solutions. Significantly, for the most concentrated solutions, as the probe particle size was varied from 0.3 to 2.2 microm, the observed mean square displacement deviated substantially from the generalized Stokes-Einstein behavior predicted by microrheological theories. Our experiments showed that these deviations could not be attributed to specific physicochemical interactions at the probe-matrix interface, since observed mean square displacements were independent of different probe surface chemistries studied. Moreover, this particle size effect was not observed in semidilute, high molecular weight PEO solutions (molecular weight 4.0 x 10(6) g/mole). We concluded that possible effects of AP network compressibility and AP depletion at the probe surface could not account for the observed particle size effects. We examined recent reports of the structural heterogeneity in AP solutions for their possible connection to our observation of the breakdown of the generalized Stokes-Einstein equation for this system. Numerical conversion of the microscopic results to the linear viscoelastic moduli, G'(omega) and G"(omega), by means of a constrained regularization method (CONTIN), demonstrates that the experiments with larger probe particles are most consistent with the single-mode Maxwell model LVE observed by macroscopic mechanical rheology.

Diffusion of Model Hydrophobic Alkali-Swellable Emulsion Associative Thickeners

Diffusion coefficients of hydrophobically modified alkali-swellable (HASE) associating polymers (APs) in aqueous solution were measured using pulsed gradient spin-echo (PGSE) nuclear magnetic resonance (NMR). HASE APs consist of a copolymer of methacrylic acid and ethyl acrylate to which hydrophobic “sticker groups” are attached through a poly(ethylene oxide) (PEO) “spacer arm”. Two series of HASE APs were investigated: one in which the length of the hydrophobic alkyl chain was varied (CxE35) and another in which the length of the PEO spacer arm was varied (C20Ey). With increasing hydrophobe or PEO spacer arm length the average diffusion coefficient decreased, reflecting the viscosity enhancement produced by the associating network formed by HASE polymers. The effect of external variables such as concentration, pH, and temperature mirrored established rheological properties for such systems. The average diffusion behavior, however, was the result of a superposition of two contributions, one slow (D0 < 1 × 10-11 m2 s-1) and one fast (D0 ≈ 1 × 10-10 m2 s-1) diffusing. Changing the hydrophobe chain length or the PEO spacer arm length modulated the proportion of the fast and slow diffusing populations but had relatively little effect on the diffusion coefficients of the two populations. Precipitation of the HASE AP from THF−HClaq produced two fractions, one enriched with hydrophobe and the other correspondingly depleted relative to the global average. The fractions enriched and depleted with respect to hydrophobe exhibited diffusion coefficients similar to the fast and slow diffusing populations. We conclude that the hydrophobe is inhomogeneously distributed among the HASE AP chains, that the population enriched with hydrophobe forms more compact structures capable of faster diffusion, and that the effects of hydrophobe chain length and PEO spacer arm length on HASE AP solution viscosity are mediated by their influence on the coupling of the hydrophobe enriched population into the slow-diffusing hydrophobe-depleted population.

Structure and Dynamics of Associative Water-Soluble Polymer Aggregates As Seen by19F NMR Spectroscopy

The microstructure and the molecular dynamics of aqueous solutions of an associative polymer (AP), consisting of a polyelectrolyte backbone and attached perfluorocarbon side chains, have been studied by 19F NMR. The spectral shape and the distributions of the molecular self-diffusion coefficient and of the transverse and the longitudinal relaxation rates along the 19F spectrum have been measured, together with the magnetic field dependence of the relaxation rates. A comprehensive analysis yields that the spectral lines are broadened by a chemical shift distribution that reflects the distribution of the average hydrophobicity of the environment within the aggregates in which the perfluorocarbon side chains reside. A fraction of the AP chains remain unaggregated with all their side chains immersed in water. As shown by the NMR data, the exchange time of the APs among different states of aggregation is long, >1 s, while the exchange time of individual side chains among aqueous and hydrophobic environments wi...

Using End-Confined Chains To Model End-Absorbing, Triblock Copolymers: 1. Analytical Approach

The bridging attraction, mediated by associative, triblock copolymers with insoluble end blocks and a soluble spacer block, is analyzed using scaling arguments and analytical methods. Adsorbing these associative polymers (APs) onto a single surface, the approach of another, bare, surface results in a strong bridging attraction. When both slit surfaces bear adsorbed APs, the bridging attraction is much weaker. The main contribution is an entropic gain since bridge formation decreases the monomer number density in the crowded region near the surface.

Using End-Confined Chains To Model End-Absorbing, Triblock Copolymers: 2. Numerical Approach

The bridging attraction mediated by end-absorbing, triblock copolymers in a good solvent is analyzed using numerical methods and compared to analytical results. Good agreement is found. The main deviations may be attributed to the neglect of thermal fluctuations in the extension of the loops at the brush edge in the analytical treatment. With a suitable choice of “natural” units, the numerical results for the bridging probability and the free energy of interaction per chain collapse onto universal master curves in the two arrangements considered: symmetric and asymmetric adsorption of associative polymers (APs) on the surfaces of a planar slit.

A Comparison between Hydrophobically End-Capped Poly(ethylene oxide) with Ether and Urethane Bonds

Two models of HEUR (hydrophobically modified ethylene oxide urethane) associative polymers (AP) are compared. The two polymers are polyethyleneoxides simply end-capped with dodecyl groups, one through an ether bond H25C12–O–(CH2CH2O)304–C12H25(AP14,Mw= 13,700) and the other through an urethane bond H25C12–NHCOO–(CH2CH2O)304–CONH–C12H25(AP14NCO,Mwis about the same as for AP14). The results indicate that this subtle difference in polymer architecture dramatically influences the initial association and the clouding of the polymer in water, so that AP14NCO starts to aggregate earlier but has a higher clouding temperature. However, at more elevated polymer contents (above 2–3 wt%) the differences in solution behavior and transport dynamics between the two polymers seems less significant. These conclusions are drawn through fluorescence, dynamic light scattering, NMR self-diffusion, turbidimetry, and viscosity measurements.

Water Self-Diffusion in Aqueous Associative Polymer Solutions

Water self-diffusion in aqueous model associative polymer (AP) solutions, hydrophobically end-capped poly(ethylene oxide), C12EO200C12 (AP9,) and C12EO90C12 (AP4), has been studied with the NMR-PGSE method and compared to the diffusion in nonmodified poly(ethylene oxide) PEO. It was found that it decreases monotonically with increasing polymer concentration, giving Di/D0 ≈ 0.2 at 50 wt % (D0 being the water self-diffusion coefficient in the absence of polymer), independently of polymer molecular weight and modification. In further evaluation of the data, the cell-diffusion model was used. Such an analysis suggests that up to a polymer content of about 2 wt % AP9, water diffusion is not significantly affected by the polymer. Above this concentration, up to about 10 water molecules per EO group are affected in AP9 and AP4 solutions. On increasing the temperature, water self-diffusion increases, following an Arrhenius-like equation, with Ea equal to that of pure water at low polymer content (10 wt %). The ac...

Effect of Temperature on NMR Self-Diffusion in Aqueous Associative Polymer Solutions

The temperature dependence of polymer self-diffusion rates in aqueous solutions of C12EO200C12 (AP9, Mw = 9300) and C12EO90C12 (AP4, Mw = 4600) and nonmodified analogues PEO10 and PEO4 (Mw = 10 000 and 3400) has been studied. The effect of the hydrophobic end-groups on the self-diffusion of the associative polymer (AP) was found to be proportional to the polymer content and inversely related to the temperature. The variation of the AP self-diffusion coefficient follows an Arrhenius behavior. The resulting apparent activation energies, Ea, increase with polymer content from 15 to 55 kJ/mol in the range 0.5−50 wt % for AP9, whereas the parent PEO10 shows an almost constant Ea of about 25 kJ/mol in the same concentration range. Activation energies derived from self-diffusion and low shear viscosity measurements were found to be quite similar. The distribution of self-diffusion coefficients often observed in AP systems is discussed in terms of distribution of aggregate sizes at low AP content and homogeneity ...

Surfactant Interactions with HEUR Associating Polymers

The interactions between a HEUR (hydrophobically-modified ethoxylated urethane) AP (associating polymer) and the anionic surfactant SDS (sodium dodecyl sulfate) or the cationic surfactant DTAB (dodecyltrimethylammonium bromide) were studied using a combination of rheology measurements plus PGSE (pulsed-gradient spin-echo) NMR self-diffusion and NMR relaxation time measurements. For comparison, parallel experiments were performed using poly(ethylene oxide) (PEO) plus surfactant mixtures. At low concentrations (4 SDS per HEUR AP hydrophobe) added surfactant enhanced HEUR AP network formation. At high concentrations (33 SDS per HEUR AP hydrophobe) added surfactant totally disrupted the HEUR AP network and the HEUR AP self-diffusion came to resemble that of PEO. Both SDS and DTAB bound with greater affinity to the HEUR AP than to PEO. SDS bound with greater affinity than DTAB to either the HEUR AP or PEO. Despite the association of SDS with the ethylene oxide backbone of the HEUR AP, the results support the hydrophobe-replacement model as a description of the effects of surfactant on network formation in solutions of HEUR APs.

NMR Diffusion and Relaxation Time Studies of HEUR Associating Polymer Binding to Polystyrene Latex

Binding of a HEUR (hydrophobic ethoxylated urethane) associating polymer (AP) (MW 51 000, C16 hydrophobic end caps) to polystyrene latex (diameter 168 nm) was investigated by a combination of NMR diffusion, relaxation time, and adsorption measurements. Adsorption of the HEUR AP to the latex particles could be quantified by 1H NMR using a depletion method and could be described by a Langmuir isotherm. The latex-bound HEUR AP exhibited a spin−lattice relaxation time (T1) identical to that measured in bulk solution. The spin−spin relaxation time (T2) of the adsorbed HEUR AP was, however, much shorter than that measured in bulk solution, an effect attributed to the slow rotational tumbling of the large latex particles. Diffusion of the free HEUR AP remaining in solution upon addition of latex was enhanced due to depletion of the polymer concentration in the bulk solution and the consequent breakup of the associated network. Diffusion of the latex-bound HEUR AP reflected the diffusion of the latex particles themselves.

Interaction of Hydrophobically End-Capped Poly(ethylene oxide) with Nonionic Surfactants in Aqueous Solution. Fluorescence and Light Scattering Studies

In ternary mixtures of an associative polymer (AP), hydrophobically end-capped poly(ethylene oxide), C(12)EO(460)C(12), and the nonionic surfactant, C(12)E(8), hydrophobic microdomains are formed a ...