The functionality of associative polymer networks: the association behavior of hydrophobically modified urethane-ethoxylate (HEUR) associative polymers in aqueous solution

Yekta, Ahmad; Li, Lin; Masoumi, Zahra; Winnik, Mitchell A.

doi:10.1016/0927-7757(96)03558-3

Cited by 93 publications

(136 citation statements)

References 17 publications

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“…Mistry et al reported non-single Maxwell relaxation modulus data for relatively high concentration poly(butylene oxide)-(etylene oxide)-(butylene oxide) triblock copolymer solutions [30]. Some shear relaxation modulus data for relatively high concentration HEUR solutions [2,4] also deviate from the single Maxwellian form.…”

Section: B Resultsmentioning

confidence: 99%

“…Clearly, such interactions or spatial correlations depend on the polymer concentration, and thus we expect the rheological properties of telechelic polymer solutions to be rather strongly dependent on the concentration. Indeed, we can find rather strong concentration dependence of several rheological properties in literature [2,4].…”

Section: Introductionmentioning

confidence: 99%

“…Such a network structure shows various kinds of interesting rheological behavior and rheological properties of telechelic associative polymer solutions have been extensively studied. For example, various experimental results have been reported for hydrophobically modified ethoxylated urethane (HEUR) aqueous solutions [2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

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Concentration dependence of rheological properties of telechelic associative polymer solutions

2012

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We consider concentration dependence of rheological properties of associative telechelic polymer solutions. Experimental results for model telechelic polymer solutions show rather strong concentration dependence of rheological properties. For solutions with relatively high concentrations, linear viscoelasticity deviates from the single Maxwell behavior. The concentration dependence of characteristic relaxation time and moduli is different in high and low concentration cases. These results suggest that there are two different concentration regimes. We expect that densely connected (well percolated) networks are formed in high-concentration solutions, whereas sparsely connected (weakly percolated) networks are formed in low-concentration solutions. We propose single chain type transient network models to explain experimental results. Our models incorporate the spatial correlation effect of micellar cores and average number of elastically active chains per micellar core (the network functionality). Our models can reproduce non-single Maxwellian relaxation and nonlinear rheological behavior such as the shear thickening and thinning. They are qualitatively consistent with experimental results. In our models, the linear rheological behavior is mainly attributable to the difference of network structures (functionalities). The nonlinear rheological behavior is attributable to the nonlinear flow rate dependence of the spatial correlation of micellar core positions.

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Section: B Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Concentration dependence of rheological properties of telechelic associative polymer solutions

2012

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“…Furthermore, optical experiments [20][21][22] have been made for solutions of HEUR chains containing fluorescent pyrenyl (Py) groups, either chemically attached to the chain end 20) or just dissolved in the solutions, 13,21,22) to detect the fluorescent emission from excimers formed by the Py groups associated in the hydrophobic cores. We may utilize the fluorescent emission data to estimate, for example, the fraction of dangling chain ends in solutions.…”

Section: -10)mentioning

confidence: 99%

Rheology of Aqueous Solution of Hydrophobically Modified Ethoxylated Urethane (HEUR) with Fluorescent Probes at Chain Ends: Thinning Mechanism

Suzuki

Uneyama

Inoue

et al. 2012

J. Soc. Rheol., Jpn

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Nonlinear flow behavior and the corresponding fluorescent behavior were examined for a 3.0 wt% aqueous solution of hydrophobically modified ethoxylated urethane (HEUR; M w = 1.1×10 5 ) having fluorescent pyrenyl (Py) groups at the chain ends. These end groups associated with each other to serve as cores of HEUR flower micelles, and these micelles were further connected into super-bridges to form a transient network. Correspondingly, single-Maxwellian relaxation reflecting the thermal reorganization of this network was observed in the linear viscoelastic regime. Under steady shear flow, the HEUR solution exhibited thinning of both viscosity h (g 4 ) and first normal stress coefficient Y 1 (g 4 ) at shear rates g 4 above the equilibrium relaxation frequency 1/t . Fluorescent emission intensity I E (g 4 ) from excimers formed by Py groups associated in a hydrophobic environment of the micellar cores and the intensity I M (g 4 ) from dissociated Py groups (referred to as monomers) isolated in the aqueous phase were measured under flow simultaneously with h and Y 1 . The I E /I M ratio was found to decrease only slightly (by a factor of ~4 %) on an increase of g 4 up to 6/t well in the thinning regime. (For g 4 = 6/t , h and Y 1 decreased from respective zero-shear values by factors of ~50 % and ~75 %, respectively) Thus, the significant thinning at those g 4 was accompanied by a negligible change in the HEUR core structure that corresponds to just a slight shift of the association/dissociation balance of the Py groups to the dissociated state. From this result, the thinning is quite possibly attributed to flow-induced disruption of the network connectivity through conversion of the super-bridges into super-loops, both having the same core structure.

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“…Examples of the complex rheological behavior exhibited by these polymeric networks include the ability to form highly viscous solutions at low to moderate concentrations, a linear viscoelastic response that closely resembles that of a perfect Maxwell fluid with a single relaxation time, 5,11,12 shear thickening at moderate shear rates in steady shear flow followed by marked shear thinning at high shear rate, [13][14][15][16][17][18][19] an Arrheniuslike temperature dependence of the zero-shear rate viscosity, 5,20 and a decrease in the critical shear rate at which onset of shear thickening occurs as the association strength or concentration increases or temperature decreases. 21 Recently, Ng et al 20 disputed the assertion of a single relaxation time suggested by Annable et al 5 and demonstrated that HEUR polymers in fact possesses a dual relaxation behavior.…”

Section: Introductionmentioning

confidence: 99%

Rheology and Dynamics of Associative Polymers in Shear and Extension: Theory and Experiments

2006

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We investigate the steady and transient shear and extensional rheological properties of a series of model hydrophobically modified ethoxylate-urethane (HEUR) polymers with varying degrees of hydrophobicity. A new nonlinear two-species network model for these telechelic polymers is described which incorporates appropriate molecular mechanisms for the creation and destruction of elastically active chains. Like other recent models we incorporate the contributions of both the bridging chains (those between micelles) and the dangling chains to the final stress tensor. This gives rise to two distinct relaxation time scales: a short Rouse time for the relaxing chains and a longer network time scale that depends on the aggregation number and strength of the micellar junctions. The evolution equations for the fraction of elastically active chains and for the conformation tensors of each species are solved to obtain the total stress arising from imposed deformations. The model contains a single adjustable nonlinear parameter and incorporates the nonlinear chain extension, the shear-induced enhancement of associations, and the stretch-induced dissociation of hydrophobic chains. In contrast to earlier closed-form models, we are able to obtain quantitative agreement between experimental measurements and the model predictions for three different series of telechelic polymers over a range of concentrations. The scaling of both the zero shear viscosity and the effective network relaxation time shows good agreement with those measured in experiments. The model also quantitatively captures both the shear thickening and subsequent shear thinning observed in the rheology at high deformation rates and predicts transient extensional stress growth curves in close agreement with those measured using a filament stretching rheometer.

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The functionality of associative polymer networks: the association behavior of hydrophobically modified urethane-ethoxylate (HEUR) associative polymers in aqueous solution

Cited by 93 publications

References 17 publications

Concentration dependence of rheological properties of telechelic associative polymer solutions

Concentration dependence of rheological properties of telechelic associative polymer solutions

Rheology of Aqueous Solution of Hydrophobically Modified Ethoxylated Urethane (HEUR) with Fluorescent Probes at Chain Ends: Thinning Mechanism

Rheology and Dynamics of Associative Polymers in Shear and Extension: Theory and Experiments

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