Reversible shear gelation of polymer-clay dispersions

Danilo C. Pozzo; Lynn M. Walker

doi:10.1016/j.colsurfa.2004.04.040

Reversible shear gelation of polymer-clay dispersions

Danilo C. Pozzo, Lynn M. Walker

Research output: Contribution to journal › Article › peer-review

76 Scopus citations

Abstract

Reversible, shear-induced gelation of semi-dilute aqueous colloidal dispersions consisting of monodisperse discoid particles (Laponite) and weakly adsorbing polymer (polyethylene oxide) is studied through a combination of small angle neutron scattering and oscillatory shear. When shaken the samples undergo a dramatic transition from a low viscosity fluid to a self-supporting, turbid gel. This complex non-linear behavior is found to occur over a narrow composition regime near a composition commensurate with saturation of the clay surface with polymer. Through a combination of SANS and rheology, shear gelation is found to occur through the deformation of large stable flocs that expose fresh surface area for the formation of new polymer bridges. At rest, the temporary shear-induced flocs slowly fractionate with time as the polymer desorbs from the clay surface. The shear-induced gelation is time reversible and strongly temperature-dependent suggesting that relaxation is an activated process. Samples showing shear induced gelation are also able to form stiff stable gels which are characteristically similar to pure clay dispersions.

Original language	English (US)
Pages (from-to)	187-198
Number of pages	12
Journal	Colloids and Surfaces A: Physicochemical and Engineering Aspects
Volume	240
Issue number	1-3
DOIs	https://doi.org/10.1016/j.colsurfa.2004.04.040
State	Published - Jun 15 2004
Externally published	Yes

Bibliographical note

Funding Information:
The authors would like to acknowledge Southern Clay products for donation of the clay particles. DCP acknowledges the PPG Fellowship fund at CMU for providing funding during the completion of this work. We are above all grateful to L. Porcar, V. Prasad and D. Weitz for insightful conversations. We also acknowledge the support of the National Institute of Standards and Technology, US. Department of Commerce, in providing the neutron research facilities used in this work. This work utilized facilities supported in part by the National Science Foundation under Agreement No. DMR-9986442.

Keywords

Gel
Nanoparticles
Neutron scattering
Polymer
Rheology

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10.1016/j.colsurfa.2004.04.040

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title = "Reversible shear gelation of polymer-clay dispersions",

abstract = "Reversible, shear-induced gelation of semi-dilute aqueous colloidal dispersions consisting of monodisperse discoid particles (Laponite) and weakly adsorbing polymer (polyethylene oxide) is studied through a combination of small angle neutron scattering and oscillatory shear. When shaken the samples undergo a dramatic transition from a low viscosity fluid to a self-supporting, turbid gel. This complex non-linear behavior is found to occur over a narrow composition regime near a composition commensurate with saturation of the clay surface with polymer. Through a combination of SANS and rheology, shear gelation is found to occur through the deformation of large stable flocs that expose fresh surface area for the formation of new polymer bridges. At rest, the temporary shear-induced flocs slowly fractionate with time as the polymer desorbs from the clay surface. The shear-induced gelation is time reversible and strongly temperature-dependent suggesting that relaxation is an activated process. Samples showing shear induced gelation are also able to form stiff stable gels which are characteristically similar to pure clay dispersions.",

keywords = "Gel, Nanoparticles, Neutron scattering, Polymer, Rheology",

author = "Pozzo, {Danilo C.} and Walker, {Lynn M.}",

note = "Funding Information: The authors would like to acknowledge Southern Clay products for donation of the clay particles. DCP acknowledges the PPG Fellowship fund at CMU for providing funding during the completion of this work. We are above all grateful to L. Porcar, V. Prasad and D. Weitz for insightful conversations. We also acknowledge the support of the National Institute of Standards and Technology, US. Department of Commerce, in providing the neutron research facilities used in this work. This work utilized facilities supported in part by the National Science Foundation under Agreement No. DMR-9986442. ",

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AU - Walker, Lynn M.

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PY - 2004/6/15

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N2 - Reversible, shear-induced gelation of semi-dilute aqueous colloidal dispersions consisting of monodisperse discoid particles (Laponite) and weakly adsorbing polymer (polyethylene oxide) is studied through a combination of small angle neutron scattering and oscillatory shear. When shaken the samples undergo a dramatic transition from a low viscosity fluid to a self-supporting, turbid gel. This complex non-linear behavior is found to occur over a narrow composition regime near a composition commensurate with saturation of the clay surface with polymer. Through a combination of SANS and rheology, shear gelation is found to occur through the deformation of large stable flocs that expose fresh surface area for the formation of new polymer bridges. At rest, the temporary shear-induced flocs slowly fractionate with time as the polymer desorbs from the clay surface. The shear-induced gelation is time reversible and strongly temperature-dependent suggesting that relaxation is an activated process. Samples showing shear induced gelation are also able to form stiff stable gels which are characteristically similar to pure clay dispersions.

AB - Reversible, shear-induced gelation of semi-dilute aqueous colloidal dispersions consisting of monodisperse discoid particles (Laponite) and weakly adsorbing polymer (polyethylene oxide) is studied through a combination of small angle neutron scattering and oscillatory shear. When shaken the samples undergo a dramatic transition from a low viscosity fluid to a self-supporting, turbid gel. This complex non-linear behavior is found to occur over a narrow composition regime near a composition commensurate with saturation of the clay surface with polymer. Through a combination of SANS and rheology, shear gelation is found to occur through the deformation of large stable flocs that expose fresh surface area for the formation of new polymer bridges. At rest, the temporary shear-induced flocs slowly fractionate with time as the polymer desorbs from the clay surface. The shear-induced gelation is time reversible and strongly temperature-dependent suggesting that relaxation is an activated process. Samples showing shear induced gelation are also able to form stiff stable gels which are characteristically similar to pure clay dispersions.

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KW - Neutron scattering

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KW - Rheology

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Reversible shear gelation of polymer-clay dispersions

Abstract

Bibliographical note

Keywords

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