Special Issue "Complex Fluid Rheology"

A special issue of Polymers (ISSN 2073-4360).

Deadline for manuscript submissions: closed (30 June 2017)

Special Issue Editor

Guest Editor
Prof. Dr. Patrick Underhill

Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, NY 12180, USA
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Interests: large amplitude oscillatory shear; extensional flow; interfacial rheology; microrheology; coarse-graining simulation methods; molecular dynamics; biopolymer physics; active matter; swimming microorganisms; microfluidics

Special Issue Information

Dear Colleagues,

This Special Issue of Polymers is dedicated to the complex fluid rheology of polymeric materials. The complex rheology of such materials plays an important role in many applications. This issue aims to reflect the current work and progress in how the microstructure causes the rheological response and how the rheology influences other properties of the system. Contributions with experimental work, computational work, or combinations of the two are welcome. Topics may include measuring or determining computationally the rheological properties such as in large amplitude oscillatory shear (LAOS), in extensional flows, at interfaces, or using microrheology. They could also focus on the rheology specific to types of polymeric materials such as associating polymers, polyelectrolytes, gels, etc. Finally, the role of polymer rheology in producing phenomena, such as elastic instabilities, are of interest.

Prof. Dr. Patrick Underhill
Guest Editor

Manuscript Submission Information

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Keywords

  • Complex fluids
  • Large amplitude oscillatory shear
  • Extensional rheology
  • Interfacial rheology
  • Microrheology
  • Associating polymers
  • Polyelectrolytes
  • Gel rheology
  • Elastic instabilities

Published Papers (6 papers)

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Research

Open AccessArticle
Microstructural Origins of Nonlinear Response in Associating Polymers under Oscillatory Shear
Polymers 2017, 9(11), 556; https://doi.org/10.3390/polym9110556
Received: 29 June 2017 / Revised: 22 October 2017 / Accepted: 24 October 2017 / Published: 26 October 2017
Cited by 1 | PDF Full-text (4198 KB) | HTML Full-text | XML Full-text
Abstract
The response of associating polymers with oscillatory shear is studied through large-scale simulations. A hybrid molecular dynamics (MD), Monte Carlo (MC) algorithm is employed. Polymer chains are modeled as a coarse-grained bead-spring system. Functionalized end groups, at both ends of the polymer chains, [...] Read more.
The response of associating polymers with oscillatory shear is studied through large-scale simulations. A hybrid molecular dynamics (MD), Monte Carlo (MC) algorithm is employed. Polymer chains are modeled as a coarse-grained bead-spring system. Functionalized end groups, at both ends of the polymer chains, can form reversible bonds according to MC rules. Stress-strain curves show nonlinearities indicated by a non-ellipsoidal shape. We consider two types of nonlinearities. Type I occurs at a strain amplitude much larger than one, type II at a frequency at which the elastic storage modulus dominates the viscous loss modulus. In this last case, the network topology resembles that of the system at rest. The reversible bonds are broken and chains stretch when the system moves away from the zero-strain position. For type I, the chains relax and the number of reversible bonds peaks when the system is near an extreme of the motion. During the movement to the other extreme of the cycle, first a stress overshoot occurs, then a yield accompanied by shear-banding. Finally, the network restructures. Interestingly, the system periodically restores bonds between the same associating groups. Even though major restructuring occurs, the system remembers previous network topologies. Full article
(This article belongs to the Special Issue Complex Fluid Rheology)
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Open AccessArticle
The Impotence of Non-Brownian Particles on the Gel Transition of Colloidal Suspensions
Polymers 2017, 9(9), 461; https://doi.org/10.3390/polym9090461
Received: 7 July 2017 / Revised: 17 August 2017 / Accepted: 14 September 2017 / Published: 19 September 2017
Cited by 2 | PDF Full-text (10394 KB) | HTML Full-text | XML Full-text
Abstract
The ability to predict transitions in the microstructure of mixed colloidal suspensions is of extreme interest and importance. The data presented here is specific to the case of battery electrode slurries whereby the carbon additive is reported to form strong colloidal gels. Using [...] Read more.
The ability to predict transitions in the microstructure of mixed colloidal suspensions is of extreme interest and importance. The data presented here is specific to the case of battery electrode slurries whereby the carbon additive is reported to form strong colloidal gels. Using rheology, we have determined the effect of mixed particle systems on the critical gel transition ϕ gel . More specifically, we show that the introduction of a high volume fraction of large non-Brownian particles has little to no effect on ϕ gel . Although ϕ gel is unchanged, the larger particles do change the shape of the linear viscoelasticity and the nonlinear yielding behavior. There are interesting similarities to the nonlinear behavior of the colloidal gels with trends observed for colloidal glasses. A comparison of experimental data and the prediction from theory shows that the equation presented by Poon et al. is able to quantitatively predict the transition from a fluid state to a gel state. Full article
(This article belongs to the Special Issue Complex Fluid Rheology)
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Open AccessArticle
Theoretical Analysis of Critical Flowable Physical Gel Cross-Linked by Metal Ions and Polyacrylamide-Derivative Associating Polymers Containing Imidazole Groups
Polymers 2017, 9(7), 256; https://doi.org/10.3390/polym9070256
Received: 19 May 2017 / Revised: 18 June 2017 / Accepted: 23 June 2017 / Published: 29 June 2017
Cited by 1 | PDF Full-text (6202 KB) | HTML Full-text | XML Full-text
Abstract
When the polymer chains are cross-linked by physical bonds having a finite lifetime, the relaxation time and viscosity do not diverge at the gel point though percolation occurs. These undivergent quantities are related to the finite-sized “largest relaxed cluster,” which can relax before [...] Read more.
When the polymer chains are cross-linked by physical bonds having a finite lifetime, the relaxation time and viscosity do not diverge at the gel point though percolation occurs. These undivergent quantities are related to the finite-sized “largest relaxed cluster,” which can relax before it breaks. Its size is the key rheological parameter characterizing of the critical physical gels. In order to evaluate this characteristic size, we propose here a generalized phenomenological model for the viscoelasticity of critical physical gels. We apply the theory to the previously reported experimental result for the physical gel consisting of polyacrylamide-derivative associating polymers containing imidazole groups cross-linked by coordination bonds with Ni ions. We successfully estimate the size of the largest relaxed cluster and the fractal dimension. The size is in good agreement with that estimated from the mean-square displacement of probe particles at the gel point by microrheological measurement. We also compare this system with the poly(vinyl alcohol) hydrogel cross-linked by borate ions, and show that the difference in the cluster structures is originating from the differences of precursor chain properties such as overlap concentration and radius of gyration and of the cross-linking states in these systems. Full article
(This article belongs to the Special Issue Complex Fluid Rheology)
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Open AccessArticle
Two Ways to Examine Differential Constitutive Equations: Initiated on Steady or Initiated on Unsteady (LAOS) Shear Characteristics
Polymers 2017, 9(6), 205; https://doi.org/10.3390/polym9060205
Received: 21 April 2017 / Revised: 29 May 2017 / Accepted: 1 June 2017 / Published: 3 June 2017
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Abstract
The exponential Phan–Tien and Tanner (PTT), Giesekus, Leonov, and modified extended Pom–Pom (mXPP) differential constitutive models are evaluated in two ways: with regard to steady shear characteristics and with regard to large amplitude oscillatory shear characteristics of a solution of poly(ethylene oxide) in [...] Read more.
The exponential Phan–Tien and Tanner (PTT), Giesekus, Leonov, and modified extended Pom–Pom (mXPP) differential constitutive models are evaluated in two ways: with regard to steady shear characteristics and with regard to large amplitude oscillatory shear characteristics of a solution of poly(ethylene oxide) in dimethyl sulfoxide. Efficiency of the models with nonlinear parameters optimized with respect to steady shear measurements is evaluated by their ability to describe large amplitude oscillatory shear (LAOS) characteristics. The reciprocal problem is also analyzed: The nonlinear parameters are optimized with respect to the LAOS measurements, and the models are confronted with the steady shear characteristics. In this case, optimization is based on the LAOS measurements and equal emphasis is placed on both real and imaginary parts of the stress amplitude. The results show that the chosen models are not adequately able to fit the LAOS characteristics if the optimization of nonlinear parameters is based on steady shear measurements. It follows that the optimization of nonlinear parameters is much more responsible if it is carried out with respect to the LAOS data. In this case, when the optimized parameters are used for a description of steady shear characteristics, efficiency of the individual models as documented differs. Full article
(This article belongs to the Special Issue Complex Fluid Rheology)
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Open AccessArticle
Structural Features and the Anti-Inflammatory Effect of Green Tea Extract-Loaded Liquid Crystalline Systems Intended for Skin Delivery
Polymers 2017, 9(1), 30; https://doi.org/10.3390/polym9010030
Received: 14 November 2016 / Revised: 21 December 2016 / Accepted: 12 January 2017 / Published: 18 January 2017
Cited by 4 | PDF Full-text (2391 KB) | HTML Full-text | XML Full-text
Abstract
Camellia sinensis, which is obtained from green tea extract (GTE), has been widely used in therapy owing to the antioxidant, chemoprotective, and anti-inflammatory activities of its chemical components. However, GTE is an unstable compound, and may undergo reactions that lead to a [...] Read more.
Camellia sinensis, which is obtained from green tea extract (GTE), has been widely used in therapy owing to the antioxidant, chemoprotective, and anti-inflammatory activities of its chemical components. However, GTE is an unstable compound, and may undergo reactions that lead to a reduction or loss of its effectiveness and even its degradation. Hence, an attractive approach to overcome this problem to protect the GTE is its incorporation into liquid crystalline systems (LCS) that are drug delivery nanostructured systems with different rheological properties, since LCS have both fluid liquid and crystalline solid properties. Therefore, the aim of this study was to develop and characterize GTE-loaded LCS composed of polyoxypropylene (5) polyoxyethylene (20) cetyl alcohol, avocado oil, and water (F25E, F29E, and F32E) with different rheological properties and to determine their anti-inflammatory efficacy. Polarized light microscopy revealed that the formulations F25, F29, and F32 showed hexagonal, cubic, and lamellar liquid crystalline mesophases, respectively. Rheological studies showed that F32 is a viscous Newtonian liquid, while F25 and F29 are dilatant and pseudoplastic non-Newtonian fluids, respectively. All GTE-loaded LCS behaved as pseudoplastic with thixotropy; furthermore, the presence of GTE increased the S values and decreased the n values, especially in F29, indicating that this LCS has the most organized structure. Mechanical and bioadhesive properties of GTE-unloaded and -loaded LCS corroborated the rheological data, showing that F29 had the highest mechanical and bioadhesive values. Finally, in vivo inflammation assay revealed that the less elastic and consistent LCS, F25E and F32E presented statistically the same anti-inflammatory activity compared to the positive control, decreasing significantly the paw edema after 4 h; whereas, the most structured and elastic LCS, F29E, strongly limited the potential effects of GTE. Thereby, the development of drug delivery systems with suitable rheological properties may enhance GTE bioavailability, enabling its administration via the skin for the treatment of inflammation. Full article
(This article belongs to the Special Issue Complex Fluid Rheology)
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Open AccessArticle
Molecular Dynamics Simulations for Resolving Scaling Laws of Polyethylene Melts
Polymers 2017, 9(1), 24; https://doi.org/10.3390/polym9010024
Received: 13 November 2016 / Revised: 16 December 2016 / Accepted: 4 January 2017 / Published: 12 January 2017
Cited by 11 | PDF Full-text (25893 KB) | HTML Full-text | XML Full-text
Abstract
Long-timescale molecular dynamics simulations were performed to estimate the actual physical nature of a united-atom model of polyethylene (PE). Several scaling laws for representative polymer properties are compared to theoretical predictions. Internal structure results indicate a clear departure from theoretical predictions that assume [...] Read more.
Long-timescale molecular dynamics simulations were performed to estimate the actual physical nature of a united-atom model of polyethylene (PE). Several scaling laws for representative polymer properties are compared to theoretical predictions. Internal structure results indicate a clear departure from theoretical predictions that assume ideal chain statics. Chain motion deviates from predictions that assume ideal motion of short chains. With regard to linear viscoelasticity, the presence or absence of entanglements strongly affects the duration of the theoretical behavior. Overall, the results indicate that Gaussian statics and dynamics are not necessarily established for real atomistic models of PE. Moreover, the actual physical nature should be carefully considered when using atomistic models for applications that expect typical polymer behaviors. Full article
(This article belongs to the Special Issue Complex Fluid Rheology)
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