Network formation and its consequences for the physical behaviour of associating polymers in solution

Annable, Tom; Buscall, Richard; Ettelaie, Rammile

doi:10.1016/0927-7757(96)03621-7

Cited by 121 publications

(161 citation statements)

References 22 publications

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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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Section: Introductionmentioning

confidence: 99%

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

2006

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“…The reversible junctions in transient networks typically contain areas of hydrophobic associations, [7][8][9][10] hydrogen bonding, [11][12][13][14][15][16][17] metal-ligand interactions, 18,19 or ionic associations. 20,21 In many cases such junctions are poorly defined aggregates with unknown association strength and kinetics, but in a few transient network materials bulk properties have been directly correlated to defined polymer microstructure or well-characterized reversible interactions leading to important insights into the properties of these systems.…”

Section: Introductionmentioning

confidence: 99%

Model Transient Networks from Strongly Hydrogen-Bonded Polymers

Feldman¹,

Kade²,

Meijer³

et al. 2010

Macromolecules

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Random copolymers consisting of n-butyl acrylate backbones with quadruple hydrogenbonding side chains based on 2-ureido-4[1H]-pyrimidinone (UPy) have been synthesized via controlled radical polymerization and postpolymerization functionalization. Through this synthetic strategy high UPy monomer content (15 mol %) can be reached while maintaining low polydispersity and excellent control over molecular weight, providing model reversible networks with well-defined molecular architecture. Despite low T g s and a lack of entanglements or crystallinity, these materials behave as thermoplastic elastomers through the strong but reversible association of UPy groups. Bulk properties such as the plateau modulus, tensile modulus, and relaxation time scale are primarily determined by the average distance between UPy's along the chain. Starting from a difunctional initiator, triblock copolymers can also be synthesized containing a homopolymer midblock and random copolymer end blocks, effectively concentrating the hydrogen-bonding groups near the chain ends. By controlling both the average composition and distribution of UPy's along the polymer chain, macroscopic material properties such as stiffness and resistance to creep can be independently tuned.

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“…The dramatic change in rheology is due to the propagation of stress through the associative network. 23 HEUR bridges can propagate stress whereas HEURs in loop and dangling configurations cannot. 23 When stress is applied, bridges are extended, contracted, formed, broken, and reformed.…”

Section: Rheologymentioning

confidence: 99%

“…23 HEUR bridges can propagate stress whereas HEURs in loop and dangling configurations cannot. 23 When stress is applied, bridges are extended, contracted, formed, broken, and reformed. 8,23,24 The system remains as disordered as before and shows Newtonian behavior 8,23,24 ( Figure 5).…”

Section: Rheologymentioning

confidence: 99%

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Syneresis and Rheology Mechanisms of a Latex-HEUR Associative Thickener System

Smith

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Syneresis and Rheology Mechanisms of a Latex-HEUR Associative Thickener SystemTravis Bruno Smith Rheology modifiers are used in paints and coatings to ease their application to a surface, prevent sagging once applied, and allow the leveling of brushstrokes, among other benefits. The early rheology modifiers were hydroxyethyl celluloses (HECs), a type of non-associative thickener that is relatively inexpensive and synthesized from cellulose, which is abundant. However, coatings that are modified with HECs tend to suffer from poor leveling and syneresis (phase separation). HECs have since been replaced with associative thickeners (ATs). These thickeners, when properly formulated, produce stable dispersions that have improved rheological properties, yet, unlike HECs, are sensitive to changes to the coating formulation. This drawback has encouraged research that attempts to predict the phase behavior and rheology of systems that are modified with ATs.This work is concerned with the phase behavior and rheology of waterborne latex / hydrophobically-modified ethoxylated urethane (HEUR) AT systems. When latex volume fraction is held constant, the amount of HEUR (and surfactant) in the mixture determines whether the system experiences syneresis. Dispersion phase diagrams (DPDs) of such systems have been previously studied, but the rheology of the mixtures used to prepare the DPDs have not been studied in any detail. A study on the rheology of phase separated latex / HEUR mixtures that were prepared with commercial materials was done at Cal Poly and showed a correlation between syneresis and complex rheology. However, v a proper analysis was limited because the compositions and chemical structures of the commercial materials were not well known.To better understand the relationships between phase behavior and rheology, waterborne latex / HEUR mixtures were prepared from latex and HEURs that were made at Cal Poly. Three series of mixtures were studied: commercial latex / commercial HEUR (I), commercial latex / Cal Poly HEUR (II), and Cal Poly latex / Cal Poly HEUR (III).The latex volume fraction was held constant at 0.25 and the concentration of HEUR was varied from 0-2.0 wt%. Mixtures were allowed to equilibrate for 7 days, syneresis was measured on day 7, and steady-state viscosities over a shear rate range of 0.01-1000 s -1 were determined on days 7-9 with a DHR-2 rheometer (TA Instruments) that was outfitted with 40 mm, 2 o cone. The mixtures were also studied by microscopy and dynamic oscillatory testing. The chemical structures of the Cal Poly HEURs were determined by proton nuclear magnetic resonance spectroscopy ( 1 H NMR) and the molecular weight by gel permeation chromatography (GPC).From this study, a correlation between syneresis and complex rheology was observed in I. Similar trends were observed in phase-separated II and dispersed (not phase-separated) III, though II with over 0.4 wt% HEUR were ejected from the cone / plate geometry at 1-100 s -1 and III did not demonstrate syneresis. Further investi...

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Network formation and its consequences for the physical behaviour of associating polymers in solution

Cited by 121 publications

References 22 publications

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

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

Model Transient Networks from Strongly Hydrogen-Bonded Polymers

Syneresis and Rheology Mechanisms of a Latex-HEUR Associative Thickener System

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