Viscoelastic Properties Of Polymer Solutions Research Articles

Viscoelastic rheology of polymer solution probed by resonant thermal capillary fluctuation

We present a measurement of viscoelastic properties of polymer solutions using resonant thermal capillary fluctuations of the surface of a polymer solution droplet. The instantaneous deflection of a cantilever in contact with the drop surface allows for measuring the nanoscale thermal fluctuations of the interface. From the power spectral density of measured fluctuations, we determine the two components of the rheological (dynamic and elastic viscosity) response of the fluid. Our experimental results were compared with rheological measurements using a classical commercial rheometer. We find a good agreement between the two measurements. Our experiments allow to extend the range for dynamical measurements of rheological properties of the solutions up to 20 000 s−1. Furthermore, our method requires only a small volume of liquid (10 μl) to measure the viscosity and is thus suitable for measurements on precious liquids.

Time–Concentration Superposition for Linear Viscoelasticity of Polymer Solutions

The concentration dependence of linear viscoelastic properties of polymer solutions is a well-studied topic in polymer physics. Dynamic scaling theories allow qualitative predictions of polymer solution rheology, but quantitative predictions are still limited to model polymers. Meanwhile, the scaling properties of non-model polymer solutions must be determined experimentally. In present paper, the time-concentration superposition (TCS) of experimental data is shown to be a robust procedure for studying the concentration scaling properties of binary and ternary polymer solutions. TCS can not only identify whether power law scaling may exist or not, and over which concentration range, but also unambiguously estimate the concentration scaling exponents of linear viscoelastic properties for a range of non-model polymer solutions.

Refining rheological model for description of linear and nonlinear viscoelasticity of polymer systems

The article reviews the current mesoscopic modeling of flows for polymer solutions and melts of various structures. It also demonstrates the unified structure of the rheological constitutive relation, up to a certain dissipative function. Linear and nonlinear effects are considered for the simple shear and uniaxial tension of polymer melts based on the modified Vinogradov and Pokrovskii rheological model. The model can describe with adequate accuracy the linear viscoelasticity of fluid polymer systems, as well as transient processes at the shear flow and uniaxial elongation. It was compared with other experimental data for the melt of an industrial polyethylene sample. The nonlinear viscoelastic response of a polymer material was modeled at large periodic deformations. The calculation results were obtained via the Runge-Kutta approach with in-line subprograms of MATLAB IT environment. They were later compared with the experimental data for the solution of polyethylene oxide in dimethyl sulfoxide. The nonlinear behavior of the polymer sample manifested itself in the distortion of the viscoelastic response of the material at sinusoidal oscillations. In this case the shear stresses are no longer the correct harmonics and a "step" appears at the leading edge of the response. Besides, their amplitude is not proportional to the amplitude of the shift. The paper also considers the superposition of the oscillating shear flow on the simple shear. The distortion of the viscoelastic response is observed here though, unlike the high-amplitude periodic deformation, the curvatures of the upper and lower half-waves of the response differ. Since there is still no experimental data for this case, this work expects to encourage the researchers working in the field of nonlinear viscoelastic properties of polymer solutions and melts for further endeavors.

Differences in Viscoelasticity of Ophthalmic Polymer Solution after Sterilization

Polymer solution has been used for increasing viscosity of ophthalmic solution in order to prolong the retention of active drug in the eye. The ophthalmic solution must be sterilized, which may affect the rheology properties of viscosity-inducing polymers. The aim of this study was to investigate the effect of sterilization treatment on viscosity-inducing agents (i.e., poloxamer, polyvinyl alcohol; (PVA), methyl cellulose (MC), polyvinylpyrrolidone (PVP) and carbomer). The effect of membrane filtration and steam sterilization or autoclaving (121 °C, 15 Ib/inch2, 15 min) were determined. A rheometer was used to investigate the viscosity and viscoelastic properties between treated and untreated polymer solutions. The power law model, consistency index (k), and power law index (n) of polymer solution viscosity were compared. For viscoelastic properties, storage modulus and loss modulus were examined. The results demonstrated that, viscosity of carbomer and MC solution (1 and 2 %) were changed after steam sterilization. No difference in viscosity was observed for PVP, PVA and poloxamer solution, between untreated and treated samples. The storage and loss moduli of PVA solution after autoclaving were not different when comparing with the untreated polymer solution. From this study, it could be concluded that the sterilization treatment influenced the viscosity behavior and viscoelastic properties of polymer solution used as viscosity-inducing agent in ophthalmic solution. Therefore, the selection of polymer and sterilization method should be carefully considered.

Неньютоновское течение структурированных систем. XXIII. Вязкоупругие свойства полимерных растворов

Неньютоновское течение структурированных систем. XXIII. Вязкоупругие свойства полимерных растворов

Structure and Visco-Elastic Properties of Polymer Solutions for Electrospinning Fibers

The influence of the molecular mass of poly-N-vinylpyrrolidone on the rheological, visco-elastic, relaxation properties of solutions and on their structure and stability of the process of obtaining fibers by electrospinning is considered. The critical values of the concentration and molecular mass of the polymer for carrying out stable electrospinning of the fiber are established, and the relationship between the molecular mass and the concentration, viscosity of the solutions, and technological parameters of the spinning process is determined.

Effect of stretching-induced changes in hydrodynamic screening on coil-stretch hysteresis of unentangled polymer solutions

Extensional rheometry and Brownian Dynamics simulations of flexible polymer solutions confirm predictions based on blob concepts that coil--stretch hysteresis in extensional flows increases with concentration, reaching a maximum at the critical overlap concentration $c^\ast$ before progressively vanishing in the semidilute regime. These observations demonstrate that chain stretching strengthens intermolecular hydrodynamic screening in dilute solutions, but weakens it in semidilute solutions. Flow can thus strongly modify the concentration dependence of viscoelastic properties of polymer solutions.

Viscoelastic properties and structure of poly(acrylonitrile‐co‐methacrylic acid) polymer solutions for gel spinning at long aging times

ABSTRACTThe objective of the research is to obtain a more complete understanding of how aging affects the viscoelastic properties of polymer solutions to be used as starting materials for gel spinning of polymer fibers. Specifically, poly(acrylonitrile‐co‐methacrylic acid) solutions were prepared and characterized using rheological measurements and nuclear magnetic resonance spectroscopy. The results indicate that elastic character increased with increasing polymer concentration and that gelation of these solutions continued up to aging times of several weeks. Additionally, comparing the results from the two characterization methods show that while gelation continues to occur, the viscoelastic properties decrease after a critical time point suggesting that a chemical change occurs in the solutions at long times. However, these changes impact the solution dynamics minimally as the effective network properties were similar at the aging times studied here, but considerations for long‐term storage of polymer solutions for gel spinning are warranted. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39821.

Viscoelasticity of Thin Biomolecular Films: A Case Study on Nucleoporin Phenylalanine-Glycine Repeats Grafted to a Histidine-Tag Capturing QCM-D Sensor

Immobilization of proteins onto surfaces is useful for the controlled generation of biomolecular assemblies that can be readily characterized with in situ label-free surface-sensitive techniques. Here we analyze the performance of a quartz crystal microbalance with dissipation monitoring (QCM-D) sensor surface that enables the selective and oriented immobilization of histidine-tagged molecules for morphological and interaction studies. More specifically, we characterize monolayers of natively unfolded nucleoporin domains that are rich in phenylalanine-glycine repeats (FGRDs). An FGRD meshwork is thought to be responsible for the selectivity of macromolecular transport across the nuclear pore complex between the cytosol and the nucleus of living cells. We demonstrate that nucleoporin FGRD films can be formed on His-tag Capturing Sensors with properties comparable to a previously reported immobilization platform based on supported lipid bilayers (SLB). Approaches to extract the film thickness and viscoelastic properties in a time-resolved manner from the QCM-D response are described, with particular emphasis on the practical implementation of viscoelastic modeling and a detailed analysis of the quality and reliability of the fit. By comparing the results with theoretical predictions for the viscoelastic properties of polymer solutions and gels, and experimental data from an atomic force microscopy indentation assay, we demonstrate that detailed analysis can provide novel insight into the morphology and dynamics of FG repeat domain films. The immobilization approach is simple and versatile, and can be easily extended to other His-tagged biomolecules. The data analysis procedure should be useful for the characterization of other ultrathin biomolecular and polymer films.

Hydrophobically Modified Associating Polyacrylamide Solutions: Relaxation Processes and Dilational Properties at the Oil−Water Interface

The interfacial dilational viscoelastic properties of hydrophobically associating block copolymer composed of acrylamide (AM) and a low amount of 2-phenoxylethyl acrylate (POEA) (<1.0 mol %) at the octane−water interfaces were investigated by means of two methods: the interfacial tension response to sinusoidal area variations and the relaxation of an applied stress. The dependencies of interfacial dilational modulus and phase angle on the polymer concentration were explored. The influence of sodium dodecyl sulfate (SDS) on the dilational viscoelastic properties of polymer solutions was studied. The results obtained by oscillating barriers method showed that the dilational modulus passed through a maximum value with increasing polymer concentration, while the phase angle decreased with increasing concentration below 200 ppm, then showed very low concentration dependence up to 3000 ppm, and increased dramatically above it. When SDS was added to the aqueous phase, the dilational modulus passed through a maximum with increasing SDS concentration, while the change of phase angle depended on the polymer bulk concentration. The results obtained by the relaxation of an applied stress show that two main relaxation processes exist in the interface at low bulk concentration below the critical aggregation concentration: one is the fast process involving the exchange of hydrophobic microdomains between the proximal region and distal region in the interface with a characteristic time value from several tens of seconds to several seconds at different bulk concentration; the other is the slow relaxation process involving conformational changes of polymer chain in the interface with characteristic time value from 1000 s to several tens of seconds, depending on the bulk concentration. However, there is only one main relaxation process controlling the dilational properties above c*: a fast relaxation process with the characteristic relaxation time of less than 1 s, which is believed to be related to the associations formed by hydrophobic microdomains. Anionic surfactant SDS can influence the dilational properties of polymer solutions by the following ways: first, SDS can absorb onto the interface and bind to the hydrophobic microdomains to change the characteristic times and contributions of the existed relaxation processes of polymer chains; second, SDS can provide a new fast relaxation process involving the exchange of SDS molecules between monomers and mixed micelles in interface. The information on relaxation processes obtained from interfacial tension relaxation measurements can explain the results from dilational viscoelasticity measurements very well. The negative phase angles have been obtained in some case. It is believed that the in-interface slow relaxation process, which sometimes dominates the dilational viscoelasticity of polymer film, is responsible for this phenomenon in our employed experimental method.

1534 波状流路内のニュートン流体に浸透する粘弾性流体の流れ

In order to clarify the effect of viscoelastic properties of polymer solutions on the E.O.R, the flow of viscoelastic fluids penetrating into the Newtonian fluid in the axisymmetrial undulating channel was examined numerically. The viscoelastic fluids used in calculations were the Giesekus fluids with a different property of shear viscosity. In the results of this numerical calculation, it is found that the shape of the interface between the both fluids is closely connected to the viscoelastic effect.

The sol-gel transition probed by the dynamics of latex particles studied by QELS

The use of spherical probe particles to investigate the viscoelastic properties of polymer solutions has been suggested for a long time. We present, in this paper, an analysis of quasi-elastic light scattering results from latex probe particles during gelation of a gelatin solution. We show that by focusing on the short-time and long-time behavior of the autocorrelation function, it is possible to simply interpret our data in terms of the divergence of the viscosity and emergence of a shear elastic modulus near the gel point. With our crude analysis, we were able to grasp the critical behavior of gelation and obtain the two critical exponents of the transport properties.

An instrument for precise measurement of viscoelastic properties of low viscosity dilute macromolecular solutions at frequencies from 20 to 500 kHz

A high-frequency torsional rod apparatus (HFTRA) has been developed for measurements of moderately high-frequency viscoelastic properties of dilute, low viscosity polymer solutions. It employs a long cylindrically shaped resonating element driven by an X-cut (torsional mode) quartz piezoelectric crystal. Up to 11 different normal modes are employed, resulting in 11 discrete frequencies, ranging from approximately 20 to 500 kHz. Measurements are made in free decay; a key feature of the apparatus is the method for high precision measurements of damping coefficients and eigenfrequencies. The instrument is suitable for liquids with 0.003P&amp;lt;‖η*‖&amp;lt;5P and η′≥1.33η″. Typically, η′ has a relative uncertainty of ±2% or less, with the relative uncertainty for η″ being about 4% for liquids with η″ greater than 0.01P. Values of η′ obtained in the HFTRA for low viscosity liquids with small η″ show excellent agreement with the known steady flow viscosities. Measurements of the viscoelastic properties of polymer solutions employing the HFTRA and two other instruments capable of higher precision measurements show excellent agreement, demonstrating that the HFTRA is sufficiently precise for dilute-solution viscoelasticity studies; the working frequency range is such that most of the polymer relaxation time spectrum can be probed for many polymer/solvent combinations.

Effect of rubber–plasticizer interaction on temperature and concentration dependence of viscoelastic properties

Linear viscoelastic properties of polymer solutions depend on the solvent power even at high polymer concentrations. In this work, solutions of a commercial nitrile rubber in a homologous series of plasticizers were used. The rubbery plateau modulus is higher for the better solvent, the solvent power being assessed from the dilute solution viscosity.

Measurement of Viscoelastic Properties of Polymer Solutions by Torsional Crystals

The network analyzer was used for measurement of the viscoelastic properties of dilute polymer solutions. It is a sensitive instrument to measure resonance resistance and resonant frequency of crystals by the admittance circle diagrams shown on the digital oscilloscope. Measurements can be conducted more correctly and rapidly compared to the previous measuring system. Its validity was verified by measuring the complex shear modulus of dilute polymer solutions and comparing the results with the Rouse theory. The complex shear modulus was determined by measuring changes in the properties of a torsionally vibrating crystal. Frequency dependence of complex shear modulus is investigated in the frequency range from 3 to 252 kHz and temperature range from −60 to 23°C. The samples are several kinds of dilute solutions of polystyrene in toluene. The use of polystyrene is limited in narrow molecular weight fractions ranging in number-average molecular weight from 2.1×103 to 1.60×105. The results agreed with the theory by Rouse.

Solvent dynamics, local friction, and the viscoelastic properties of polymer solutions

Classical assumptions concerning the contribution of the solvent to the viscoelastic properties of polymer solutions are shown to be invalid. The presence of polymer affects the mean solvent rotational mobility, in some cases even enhancing it relative to the neat solvent case. The resulting change in local friction modify both the polymer relaxation times and the solvent contribution to the solution properties. The effect is quantified through an intrinsic «effective solvent viscosity», [η e ], which can be positive or negative

Viscoelastic properties of polymer solutions at temperatures lower than Θ points (abstract)

Zero‐shear viscosity η0 and steady‐state compliance Je of poly(α‐methylstyrenes) in benzyl n‐butyl phthalate (Θ=4.6 °C) and polystyrene in dioctyl phthalate (Θ=22 °C) were measured at temperatures lower than the Θ points. Moreover, stress developments after onset of steady shear flow were measured and the strength of entanglement was estimated on the basis of network rupture model. The concentration and the molecular weight dependences of η0 at temperatures lower than the Θ points are almost the same as those at the Θ temperatures, but the magnitude of η0 increases with decreasing temperature. This suggests that the strength of entanglement increases with decreasing solvent power. On the other hand, Je values at the temperatures lower than the Θ points are almost the same as those in good and Θ solvents. This result indicates that the entangled structure of polymer solution effective to Je is almost independent of solvent power. Therefore, it is concluded that the gel‐like behavior of polymer solution at ...

Effects of concentration and thermodynamic interaction on the viscoelastic properties of polymer solutions

Linear viscoelastic measurements are reported for solutions of a high molecular weight polybutadiene covering the entire range of concentration from pure polymer to pure solvent at 25°C in a nearly θ solvent (dioctyl phtalate) and a good solvent (phenyloctane). Three regimes of concentration are found for the viscosity in each solvent. Elastic response is also identical for the two solvents, with G° N (inferred from G″ m ) ∞1/J° e ∞φ 2.3 for φ>0.02. The results in semidilute solution compare favorably with the predictions of a recent two-parameter scaling theory

Viscoelastic Properties of Polymer Solutions at Temperatures Lower than _??_ Points

Zero-shear viscosity η0 and steady-state compliance Je of poly(α-methylstyrenes) in benzyl n-butyl phthalate (_??_=46°C) and polystyrene in dioctyl phthalate (_??_=22°C) were measured at temperatures lower than the _??_ points. Moreover, stress developments after onset of steady shear flow were measured and the strength of entanglement was estimated on the basis of network rupture model.The concentration and the molecular weight dependences of η0 at temperatures lower than the _??_ points are almost the same as those at the _??_ temperatures, but the magnitude of η0 increases with decreasing temperature. This suggests that the strength of entanglement increases with decreasing solvent power.On the other hand, Je values at the temperatures lower than the _??_ points are almost the same as those in good and _??_ solvents. This result indicates that the entangled structure of polymer solution effective to Je is almost independent of solvent power. Therefore, it is concluded that the gel-like behavior of polymer solution at temperatures lower than the _??_ points is caused by the long relaxation times due to the high viscosity.

Electrodiffusive diagnosis of the viscoelastic properties of polymer solutions on a rotating spherical electrode

This article examines the feasibility of measuring normal stresses from data from electrochemical diagnosis over the surface of a rotating sphere.