Name: studying large amplitude oscillatory shear response of soft materials
Uploaded: 2019-04-25T13:00:00
Description: Watch this Scientific Journal Video about Studying Large Amplitude Oscillatory Shear Response of Soft Materials at JoVE.com

The authors thank Anton Paar for use of the MCR 702 rheometer through their VIP academic research program. We also thank Dr. Abhishek Shetty for the comments in the instrument setup.

1. Rheometer Setup
<ol>
	<li>With the rheometer configured in the SMT mode (see note), attach the upper and lower drive geometries. To maintain as close to a homogeneous shear field as possible, use a 50 mm plate (PP50) as the lower fixture, and a 2-degree cone (CP50-2) for the upper fixture. 
	Note: The rheometer we use (see the Table of Materials) can be configured in either a combined motor-transducer (CMT) or separate motor transducer (SMT) mode. With only a single motor integrated in the rheo...

<ol>
	<li>Dolz, M., Hern&#225;ndez, M. J., Delegido, J., Alfaro, M. C., Mu&#241;oz, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+xanthan+gum+and+locust+bean+gum+upon+flow+and+thixotropic+behaviour+of+food+emulsions+containing+modified+starch.">Influence of xanthan gum and locust bean gum upon flow and thixotropic behaviour of food emulsions containing modified starch.</a> Journal of Food Engineering. 81 (1), 179-186 (2007).</li><li>Gupta, N., Zeltmann, S. E., Shunmugasamy, V. C., Pinisetty, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applications+of+Polymer+Matrix+Syntactic+Foams.">Applications of Polymer Matrix Syntactic Foams.</a> JOM. 66 (2), 245-254 (2013).</li><li>Garc&#305;a-Ochoa, F., Santos, V. E., Casas, J. 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P., Holmqvist, P., Ballesta, P., Rogers, S., Kleshchanok, D., Struth, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nonlinear+Behavior+of+Nematic+Platelet+Dispersions+in+Shear+Flow.">Nonlinear Behavior of Nematic Platelet Dispersions in Shear Flow.</a> Phys Rev Lett. 109 (24), 246001 (2012).</li><li>Hyun, K., Wilhelm, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+review+of+nonlinear+oscillatory+shear+tests:+Analysis+and+application+of+large+amplitude+oscillatory+shear+(LAOS).">A review of nonlinear oscillatory shear tests: Analysis and application of large amplitude oscillatory shear (LAOS).</a> Progress in Polymer Science. 36 (12), 1697-1753 (2011).</li><li>Park, J. D., Ahn, K. H., Lee, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+change+and+dynamics+of+colloidal+gels+under+oscillatory+shear+flow.">Structural change and dynamics of colloidal gels under oscillatory shear flow.</a> Soft Matter. 11 (48), 9262-9272 (2015).</li><li>Lee, C. -. W., Rogers, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+sequence+of+physical+processes+quantified+in+LAOS+by+continuous+local+measures.">A sequence of physical processes quantified in LAOS by continuous local measures.</a> Korea-Australia Rheology Journal. 29 (4), 269-279 (2017).</li><li>Rogers, S. A., Erwin, B. M., Vlassopoulos, D., Cloitre, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+sequence+of+physical+processes+determined+and+quantified+in+LAOS:+Application+to+a+yield+stress+fluid.">A sequence of physical processes determined and quantified in LAOS: Application to a yield stress fluid.</a> Journal of Rheology. 55 (2), 435-458 (2011).</li><li>Wagner, M. H., Rolon-Garrido, V. H., Hyun, K., Wilhelm, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+medium+amplitude+oscillatory+shear+data+of+entangled+linear+and+model+comb+polymers.">Analysis of medium amplitude oscillatory shear data of entangled linear and model comb polymers.</a> Journal of Rheology. 55 (3), 495-516 (2011).</li><li>Radhakrishnan, R., Fielding, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Shear+banding+in+large+amplitude+oscillatory+shear+(LAOStrain+and+LAOStress)+of+soft+glassy+materials.">Shear banding in large amplitude oscillatory shear (LAOStrain and LAOStress) of soft glassy materials.</a> Journal of Rheology. 62 (2), 559-576 (2018).</li><li>Bharadwaj, N. A., Ewoldt, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Constitutive+model+fingerprints+in+medium-amplitude+oscillatory+shear.">Constitutive model fingerprints in medium-amplitude oscillatory shear.</a> Journal of Rheology. 59 (2), 557-592 (2015).</li><li>Wilhelm, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fourier&#8208;Transform+Rheology.">Fourier&#8208;Transform Rheology.</a> Macromolecular Materials and Engineering. 287 (2), 83-105 (2002).</li><li>Ewoldt, R. H., Hosoi, A. E., McKinley, G. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+measures+for+characterizing+nonlinear+viscoelasticity+in+large+amplitude+oscillatory+shear.">New measures for characterizing nonlinear viscoelasticity in large amplitude oscillatory shear.</a> Journal of Rheology. 52 (6), 1427-1458 (2008).</li><li>Rogers, S. A., Lettinga, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+sequence+of+physical+processes+determined+and+quantified+in+large-amplitude+oscillatory+shear+(LAOS):+Application+to+theoretical+nonlinear+models.">A sequence of physical processes determined and quantified in large-amplitude oscillatory shear (LAOS): Application to theoretical nonlinear models.</a> Journal of Rheology. 56 (1), 1-25 (2011).</li><li>Rogers, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+sequence+of+physical+processes+determined+and+quantified+in+LAOS:+An+instantaneous+local+2D/3D+approach.">A sequence of physical processes determined and quantified in LAOS: An instantaneous local 2D/3D approach.</a> Journal of Rheology. 56 (5), 1129-1151 (2012).</li><li>Kim, J., Merger, D., Wilhelm, M., Helgeson, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microstructure+and+nonlinear+signatures+of+yielding+in+a+heterogeneous+colloidal+gel+under+large+amplitude+oscillatory+shear.">Microstructure and nonlinear signatures of yielding in a heterogeneous colloidal gel under large amplitude oscillatory shear.</a> Journal of Rheology. 58 (5), 1359-1390 (2014).</li><li>van der Vaart, K., Rahmani, Y., Zargar, R., Hu, Z., Bonn, D., Schall, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rheology+of+concentrated+soft+and+hard-sphere+suspensions.">Rheology of concentrated soft and hard-sphere suspensions.</a> Journal of Rheology. 57 (4), 1195-1209 (2013).</li><li>Poulos, A. S., Stellbrink, J., Petekidis, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow+of+concentrated+solutions+of+starlike+micelles+under+large-amplitude+oscillatory+shear.">Flow of concentrated solutions of starlike micelles under large-amplitude oscillatory shear.</a> Rheologica Acta. 52 (8-9), 785-800 (2013).</li><li>Armstrong, M. J., Beris, A. N., Rogers, S. A., Wagner, N. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+shear+rheology+of+a+thixotropic+suspension:+Comparison+of+an+improved+structure-based+model+with+large+amplitude+oscillatory+shear+experiments.">Dynamic shear rheology of a thixotropic suspension: Comparison of an improved structure-based model with large amplitude oscillatory shear experiments.</a> Journal of Rheology. 60 (3), 433-450 (2016).</li><li>Calabrese, M. A., Wagner, N. J., Rogers, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+optimized+protocol+for+the+analysis+of+time-resolved+elastic+scattering+experiments.">An optimized protocol for the analysis of time-resolved elastic scattering experiments.</a> Soft Matter. 12 (8), 2301-2308 (2016).</li></ol>

We have demonstrated how to correctly perform large amplitude oscillatory shear rheometry tests using a commercial rheometer, and to run the SPP analysis freeware to interpret and understand the nonlinear stress responses of two distinct polymer solutions. The SPP framework, which has previously been shown to correlate with structural changes and facilitate understandings of numerous colloidal systems, can be equally applied to polymer systems. The responses of two concentrated polymeric solutions to LAOS have been inves...

Concentrated polymeric solutions are used in a variety of industrial applications primarily to increase viscosity, including in foods1 and other consumer products2, enhanced oil recovery3, and soil remediation4. During their processing and use, they are necessarily subjected to large deformations over a range of timescales. Under such processes, they demonstrate rich and complex nonlinear rheological behaviors that depend on the flow or deformation conditions1. Understanding these complex nonlinear rheological behaviors is essential for successfully controlling processes, designing superior products, and maximizing energy efficiency. Aside from the industrial importance, there is a great deal of academic interest in understanding the rheological behaviors of polymeric materials far from equilibrium.
Oscillatory shear tests are a staple component of every thorough rheological characterization because of the orthogonal application of strain and strain rate5, and the ability to independently control the length and time scales probed by tuning the amplitude and frequency. The stress response to small amplitude oscillatory shear strains, which are small enough not to disturb a material&#39;s internal structure, can be decomposed into components in phase with the strain and in phase with strain rate. The coefficients of the components in phase with the strain and the strain rate are collectively referred to as the dynamic moduli6,7, and individually as the storage modulus, <img alt="Equation 1" src="/files/ftp_upload/58707/58707eq1.jpg" />, and loss modulus, <img alt="Equation 2" src="/files/ftp_upload/58707/58707eq2.jpg" />. The dynamic moduli lead to clear elastic and viscous interpretations. However, interpretations based on these dynamic moduli are valid only for small strain amplitudes, where the stress responses to sinusoidal excitations are also sinusoidal. This regime is generally referred to as the small amplitude oscillatory shear (SAOS), or the linear viscoelastic regime. As the imposed deformation becomes larger, changes are induced in the material microstructure, which are reflected in the complexity of the non-sinusoidal transient stress responses8. In this rheologically nonlinear regime, which more closely mimics industrial processing and consumer usage conditions, the dynamic moduli act as poor descriptions of the response. Another way to understand how concentrated soft materials behave out of equilibrium is therefore required.
A number of recent studies9,10,11,12,13,14,15,16 have shown that materials pass through diverse intra-cycle structural and dynamical changes elicited by larger deformations in the medium amplitude oscillatory shear (MAOS)15,17 and large amplitude oscillatory shear (LAOS) regimes. The intra-cycle structural and dynamical changes have different manifestations, such as breakage of microstructure, structural anisotropy, local rearrangements, reformation, and changes in diffusivity. These intra-cycle physical changes in the nonlinear regime lead to the complex nonlinear stress responses that cannot be simply interpreted with the dynamic moduli. As an alternative, several approaches have been suggested for the interpretation of the nonlinear stress responses. Common examples of this are Fourier transform rheology (FT rheology)18, power series expansions11, the Chebyshev description19, and the sequence of physical processes (SPP)5,8,13,14,20 analysis. Although all of these techniques have been shown to be mathematically robust, it is still an unanswered question as to whether any of these techniques can provide clear and reasonable physical explanations of nonlinear oscillatory stress responses. It remains an outstanding challenge to provide concise interpretations of rheological data that correlate to structural and dynamical measures.
In a recent study, the nonlinear stress response of the Soft Glassy Rheology (SGR) model8 and a soft glass made of colloidal star polymers7under oscillatory shear was analyzed through the SPP scheme. Temporal changes in the elastic and viscous properties inherent in nonlinear stress responses were separately quantified by the SPP moduli, <img alt="Equation 3" src="/files/ftp_upload/58707/58707eq3.jpg" /> and <img alt="Equation 4" src="/files/ftp_upload/58707/58707eq4.jpg" />. Furthermore, the rheological transition represented by the transient moduli was accurately correlated to microstructural changes represented by the distribution of mesoscopic elements. In the study of the SGR model8, it was clearly shown that rheological interpretation via the SPP scheme accurately reflects the physical changes under all oscillatory shear conditions in the linear and nonlinear regimes for soft glasses. This unique capability to provide accurate physical interpretation of nonlinear responses of soft glasses makes the SPP method an attractive approach for researchers studying out-of-equilibrium dynamics of polymer solutions and other soft materials.
The SPP scheme is built around viewing rheological behaviors as occurring in a three-dimensional space (<img alt="Equation 5" src="/files/ftp_upload/58707/58707eq5.jpg" />) that consists of the strain (<img alt="Equation 6" src="/files/ftp_upload/58707/58707eq6.jpg" />), strain rate (<img alt="Equation 7" src="/files/ftp_upload/58707/58707eq7.jpg" />), and stress (<img alt="Equation 8" src="/files/ftp_upload/58707/58707eq8.jpg" />)5. In a mathematical sense, the stress responses are treated as multivariable functions of the strain and strain rate (<img alt="Equation 9" src="/files/ftp_upload/58707/58707eq9.jpg" />). As the rheological behavior is regarded as a trajectory in <img alt="Equation 5" src="/files/ftp_upload/58707/58707eq5.jpg" /> (or a multivariable function), a tool for discussing the properties of a trajectory is required. In the SPP approach, the transient moduli <img alt="Equation 3" src="/files/ftp_upload/58707/58707eq3.jpg" /> and <img alt="Equation 4" src="/files/ftp_upload/58707/58707eq4.jpg" /> play such a role. The transient elastic modulus <img alt="Equation 3" src="/files/ftp_upload/58707/58707eq3.jpg" /> and viscous modulus <img alt="Equation 4" src="/files/ftp_upload/58707/58707eq4.jpg" /> are defined as partial derivatives of the stress with respect to the strain (<img alt="Equation 10" src="/files/ftp_upload/58707/58707eq10.jpg" />) and the strain rate (<img alt="Equation 11" src="/files/ftp_upload/58707/58707eq11.jpg" />). Following the physical definition of differential elastic and viscous moduli, the transient moduli quantify the instantaneous influence of strain and strain rate on the stress response respectively, whereas other analysis methods cannot provide any information on elastic and viscous properties separately.
The SPP approach enriches the interpretation of the oscillatory shear tests. With the SPP analysis, the complex nonlinear rheological behaviors of concentrated polymeric solutions in LAOS can be directly related to the linear rheological behaviors in SAOS. We show in this work how the maximum transient elastic modulus (<img alt="Equation 12" src="/files/ftp_upload/58707/58707eq12.jpg" />max) near the strain extrema corresponds to the storage modulus in the linear regime (SAOS). Furthermore, we show how the transient viscous modulus (<img alt="Equation 4" src="/files/ftp_upload/58707/58707eq4.jpg" />) during a LAOS cycle traces the steady state flow curve. In addition to providing details of the complex sequence of processes that concentrated polymer solutions go through under LAOS, the SPP scheme also provides information regarding the recoverable strain in the material. This information, which is not obtainable through other approaches, is a useful measure of how much a material will recoil once stress is removed. Such behavior has impact on the printability of concentrated solutions for 3D printing applications, as well as screen printing, fiber formation, and flow cessation. A number of recent studies5,8,13 clearly indicate that the recoverable strain is not necessarily the same as the strain imposed during LAOS experiments. For instance, a study of soft colloidal glasses under LAOS13 found that the recoverable strain is only 5% when significantly larger total strain (420%) is imposed. Other studies16,21,22,23,24 using the cage modulus21 also conclude that linear elasticity can be observed under LAOS at the point close to the strain maxima, implying that the materials experienced relatively small deformation at those instants. The SPP scheme is the only framework for understanding LAOS that accounts for a shift in the strain equilibrium that leads to a difference between the recoverable and the total strains.
This article aims to facilitate understandings and ease of use of the SPP analysis method by providing a detailed protocol for a LAOS analysis freeware, using two concentrated polymer solutions, a 4 wt% xanthan gum (XG) aqueous solution and a 5 wt% PEO in DMSO solution. These systems are chosen because of their broad range of application and rheologically interesting properties. Xanthan gum, a natural high-molecular-weight polysaccharide, is an exceptionally effective stabilizer for aqueous systems and commonly applied as a food additive to provide desired viscosification or in oil drilling to increase viscosity and yield points of drilling muds. PEO has a unique hydrophilic property and is often used in pharmaceutical products and controlled release systems as well as soil remediation activities. These polymeric systems are tested under various oscillatory shear conditions that are intended to approximate processing, transport, and end-use conditions. Although these practical conditions may not necessarily involve flow reversal as in oscillatory shear, the flow field can be easily approximated and tuned with the independent control of applied amplitude and imposed frequency in an oscillatory test. Furthermore, the SPP scheme can be used as described here to understand a broad range of flow types, including those that do not include flow reversals such as the recently-proposed UD-LAOS25, in which large amplitude oscillations are applied in one direction only (leading to the moniker &#34;uni-directional LAOS&#34;). For simplicity, and for illustrative purposes, we restrict the current study to traditional LAOS, which does include periodic flow reversal. The measured rheological responses are analyzed with the SPP approach. We demonstrate how to use the SPP software with simple explanations on salient calculation steps to improve readers&#39; understanding and usage. A legend for interpreting the SPP analysis results is introduced, according to which the type of rheological transition is identified. Representative SPP analysis results of the two polymers under various oscillatory shear conditions are displayed, in which we clearly identify a sequence of physical processes that contains information on the material&#39;s linear viscoelastic response as well as the steady-state flow properties of the material.
This protocol provides salient details of how to accurately perform nonlinear rheological experiments, as well as a step-by-step guide to analyzing and understanding rheological responses with the SPP framework, as shown in Figure 1. We begin by providing an introduction to the instrument setup and calibrations, followed by specific commands for making a commercially-available rheometer collect high-quality transient data. Once the rheological data have been obtained, we introduce the SPP analysis freeware, with a detailed manual. Further, we discuss how to understand the time-dependent response of the two concentrated polymer solutions within the SPP scheme, by comparing the results obtained from LAOS with the linear-regime frequency sweep and the steady-state flow curve. These results clearly identify that the polymer solutions transition between distinct rheological states within an oscillation, allowing for a more detailed picture of their nonlinear transient rheology to emerge. These data can be used to optimize processing conditions for product formation, transport, and use. These time-dependent responses further provide potential pathways to clearly form structure-property-processing relationships by coupling the rheology with microstructural information obtained from small-angle scattering of neutrons, X-rays, or light (SANS, SAXS, and SALS, respectively), microscopy, or detailed simulations.

<table>
	<tbody>
		<tr>
			<td>SPP analysis software</td>
			<td>Simon Rogers Group (UIUC)</td>
			<td>SPPplus_v1p1</td>
			<td>Attached as supplementary files</td>
		</tr>
		<tr>
			<td>MATLAB</td>
			<td>Mathwork</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Rheometer</td>
			<td>Anton Paar</td>
			<td>MCR 702 TwinDrive</td>
			<td></td>
		</tr>
		<tr>
			<td>50mm 2-degree cone</td>
			<td>Anton Paar</td>
			<td>CP50-2</td>
			<td>Upper measuring system</td>
		</tr>
		<tr>
			<td>50mm plate</td>
			<td>Anton Paar</td>
			<td>PP50</td>
			<td>Lower measuring system</td>
		</tr>
		<tr>
			<td>Xanthan gum (XG)</td>
			<td>Sigma-Aldrich</td>
			<td>11138-66-2</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyethylene oxide (PEO)</td>
			<td>Sigma-Aldrich</td>
			<td>25322-68-3</td>
			<td>Mv=1,000,000</td>
		</tr>
		<tr>
			<td>Dimethyl sulfoxide (DMSO)</td>
			<td>Sigma-Aldrich</td>
			<td>67-68-5</td>
			<td></td>
		</tr>
	</tbody>
</table>

studying large amplitude oscillatory shear response of soft materials

We investigate the sequence of physical processes exhibited during large amplitude oscillatory shearing (LAOS) of polyethylene oxide (PEO) in dimethyl sulfoxide (DMSO) and xanthan gum in water &#8212; two concentrated polymer solutions used as viscosifiers in foods, enhanced oil recovery, and soil remediation. Understanding the nonlinear rheological behavior of soft materials is important in the design and controlled manufacturing of many consumer products. It is shown how the response to LAOS of these polymer solutions can be interpreted in terms of a clear transition from linear viscoelasticity to viscoplastic deformation and back again during a period. The LAOS results are analyzed via the fully quantitative Sequence of Physical Processes (SPP) technique, using free MATLAB-based software. A detailed protocol of performing a LAOS measurement with a commercial rheometer, analyzing nonlinear stress responses with the freeware, and interpreting physical processes under LAOS is presented. It is further shown that, within the SPP framework, a LAOS response contains information regarding the linear viscoelasticity, the transient flow curves, and the critical strain responsible for the onset of nonlinearity.

Representative results of the SPP analysis from XG and PEO/DMSO solutions under oscillatory shear tests are presented in Figures 4 and 5. We first present the raw data as elastic (<img alt="Equation 30" src="/files/ftp_upload/58707/58707eq30.jpg" />) and viscous (<img alt="Equation 31" src="/files/ftp_upload/58707/58707eq31.jpg" />) Lissajous-Bowditch curves in Figures 4a, 4b, 5a and 5b. ...

Watch this Scientific Journal Video about Studying Large Amplitude Oscillatory Shear Response of Soft Materials at JoVE.com

Studying Large Amplitude Oscillatory Shear Response of Soft Materials

We present a detailed protocol outlining how to perform nonlinear oscillatory shear rheology on soft materials, and how to run the SPP-LAOS analysis to understand the responses as a sequence of physical processes.

We investigate the sequence of physical processes exhibited during large amplitude oscillatory shearing (LAOS) of polyethylene oxide (PEO) in dimethyl ...

This method can help answer key questions in the field of soft matter, such as the correlation between macroscopic and microscopic responses. The main advantage of the method is it can quantify the viscoelastic properties of materials throughout a rheological experiment in contrast to the traditional methods that provides average information. Though this method can provide insight into polymeric materials, it can also apply to other systems, such as colloidal gels and glasses and biological materials.Work with a Rheometer that can perform stain control measurements. First, attach the upper and lower drive geometries. For the lower fixture, use a 50 mm plate.Use a two degree cone for the upper fixture. Next, zero the gap, calibrate the measurements, and set the temperature. Once these steps are completed, open the gap in the geometries from zero to allow the loading material to be tested.Move on to get the material for testing. In this case, it is polyethylene oxide in DMSO, with red dye for demonstration. With a spatula, load the material onto the top of the bottom geometry.Ensure that no air bubbles are entrained in the sample in the Rheometer. Work with the measuring systems, set to trim gap. Use a square-ended spatula at the end of the geometry to gently trim excess material.Return to the measurement gap, before continuing. Run the sinusoidal oscillatory shear test using software. Navigate to My Apps.Find and open Large Amplitude Oscillatory Shear. Next, go to the measurement box. There, click the strain variable.Enter the initial and final value for a strain amplitude sweep. 1 and 4000 percent respectively. Specify the imposed frequency.Also, set the total number of strain amplitudes in the chosen range to 16. Check the Get waveform box to collect transient responses. Click the Start button to start the experiments.Data will be displayed during the course of the approximately five minute run. The Rheometer can also be used for arbitrarily defined deformations. In an external file create a list of strain values to define the function to be applied.Go to the Rheometry software and click on My Apps. And click on the waveform sign generator. In the measurement box, click on strain.From there, click on Edit. In the value list, paste the pre-determined strain values from the external file. Specify the number of points entered, the point duration and the time to adjust the imposed frequency.When done, check the Get Waveform box of the top. Then click the Start button to begin the experiment. Measurement data will appear on the monitor as the experiment proceeds.These data are for a Xanthan Gum solution under oscillatory shear tests. These non-linear stress strain curves indicate that a sequence of physical processes take place within the material. Sequence of physical processes and analysis software determines the transient moduli that signals the elastic and viscous properties of materials.Their evolution reveals behavior under large amplitude oscillatory shearing. Here, the instance of maximum elasticity are nearly constant across amplitudes. A plot of this maximum elasticity observed during large amplitude oscillatory shearing and the dynamic moduli across the range of amplitudes reveals a clear correspondence with the linear regimes storage modulus.The elastic strain determined by the sequence of physical processes software at the instance of maximum elasticity is approximately 16 percent, even when the applied strain is as large as 4000 percent. Here is a sequence of physical processes undergone by the Xanthan Gum solution. In the Viscoplastic regime, analysis indicates zero elasticity.As the shear rate decreases, the solution stiffens indicating that its structure reforms. Once sufficient strain is acquired, there is a rapid transition from elastic to viscous behavior. After yielding, the response returns to the Viscoplastic deformation regime and the sequences occurs in the opposite direction.After its development, this technique pave the way for researchers in the field of soft matter rheology, to further explore transient structure property processing relationships.

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