PolymerRheologyNationalChungCheng聚合物流变学课件

1、Chapter III Optical Characterizations第1页，共25页。3-1 Introduction to Rheo-Optics Method3-1.1. Introduction & Review of Optical Phenomena3-1.2. Characteristic Dimension & Optical Range3-2 Typical Experimental Set-ups3-2.1 Flow Dichroism and Birefringence Measurements for Case Study 1-23-2.2 Combined Rhe

2、o-Optcial Measurements (including Rheo-SALS) for Case Study 33-3 Information Retrieval in Individual MeasurementsCase Study 1: Flow Dichroism and Birefringence of PolymersCase Study 2: Dynamics of Multicomponent Polymer MeltsCase Study 3: Combined Rheo-Optcial MeasurementsReferencesTopics in Each Se

3、ction第2页，共25页。3-1.1 Introduction & Review of Optical PhenomenaA rheological measurement entails the measurement of: Force (related to the stress)Displacement (related to the strain)In a rheo-optical experiment, both the force and optical properties of the sample are measured3-1. Introduction to Rheo

4、-Optics MethodOpticalMechanicalMeasured QuantityMolecular orientation and shapeDissipation and/or storage of energyPolymer ContributionDominates the measured signalRelatively small for dilute solutionsSpatial ResolutionPossibleImpossibleMolecular LabelingPossibleImpossibleSensitivityGood precision-T

5、ime ScaleShorterLongerTable: A comparison of some important features in optical and mechanical measurements 第3页，共25页。When incident electromagnetic radiation interacts with matter, three broad classes of phenomena are of interest:Transmission of LightThe light can propagate through the material with

6、no change in direction or energy, but with a change in its state of polarizationBirefringence; “Dichroism”; TurbidityScattering RadiationThe radiation can be scattered (change in direction) with either no change in energy (elastic) or a measruable change in energy (inelastic)Static Light, X-Ray, and

7、 Neutron Scattering; Dynamic Light ScatteringAbsorption and Emission SpectroscopiesEnergy can be absorbed with the possible subsequent emission of some or all of the energyFluorescence; Phosphorescence第4页，共25页。3-1.2 Characteristic Dimension & Optical Range Typical levels of structures in polymeric s

8、ystems are listed below第5页，共25页。 The general order of structural levels that can be studied by some of the different techniques is given below第6页，共25页。3-2.1. Flow Dichroism and Birefringence of Polymers in Shear FlowsBasic Concepts:3-2. Typical Experimental Set-upsTurbidityThe Lambert-Beers Law:第7页，

9、共25页。DichriosmEX 1: Polariod Sun Glasses (A daily Eexample of dichrism resulting from absorption)EX 2: Colloids under Shear FlowFIG. Representation of a Polaroid sheet. Light with a polarisation direction parallel tothe aligned polymers is absorbed more strongly as compared to light with a polarisat

10、iondirection perpendicular to the polymersThe total amount of scattered light depends on the polarisation direction due to theanisotropic nature of the microstructure under shear flow第8页，共25页。BirefringenceMore specifically, the polarisation direction of the light can be decomposed intoa component pa

11、rallel to the direction where the refractive index is large and acomponent parallel to the direction where the refractive index is smallAfter having traversed the sample, there is a relative phase shift of the two fieldcomponents and the sum of the two fields is generally elliptically polarisedFIG.

12、Linear polarised light is generally transmitted as elliptically polarized light througha birefringent material第9页，共25页。Basic Polarimeter Design:PSGPSAFIG. Basic polarimeter schematicLight sourceSampleDetectorA Polarization State Generator, PSG, defines the polarization of the light prior to transmis

13、sionthrough the sampleA Polarization State Analyzer, PSA, determines the state of polarization of the existing light In transmission exps, one is normally concerned with the measurement of light polarizationThe Stokes Vector Entering the Detector is:The specific Mueller matrix components(optical pro

14、perties) of the sample canbe identified第10页，共25页。Example: The Crossed Polarizer SystemThe Measured Intensity I for a Sample with Coaxial Birefringence and Dichroismoriented at an Angle is:FIG. Birefringent and dichroic sample sandwiched between corssed polarizers第11页，共25页。Typical Arrangement for Flo

15、w Birefringence and Dichroism Measurements:FIG. Schematic of the experimental set-up for dichroism and birefringence measurementsA somewhat simpler set-up can be sued:Dichroism only: removal of R2, P2, and D2Turbidity only: removal of R1, R2, P2, and D2BS,BS: Beam splitterD1-D3: DetectorsP1,P2: Pola

16、rizersR1,R2: Rotating quarter wave platelets第12页，共25页。Optical Train Mounted on a Rheometerwww.chemie.uni-hamburg.de/tmc/kulicke/rheology/rheo2.htmFIG A combination of rheomechanical and rheo-optical measurements FIG Experimental apparatus for determination of flow birefringence and flow dichroism 第1

17、3页，共25页。3-2.2. Combined Rheo-Optical MeasurementsOptical Setup for Shear-Small-Angle-Light-Scattering (SALS) Mesurements Kume et al. (2019)FIG. Schematic diagram of the experimental setup for shear-light scattering: one-dimensional detector (photodiodearray), cone-and-plate type shear cell to genera

18、te Couette flow, and coordinate system used in this study第14页，共25页。FIG. Schematic diagram of the experimental setup for shear-dichroism, shear-birefringence, and rheology: (a) Schematic diagram of the combined mechanical rheometer and optical train. (b) Shear cell and optical trainOptical Setup for

19、Shear-Dichroism, Shear-Birefringence, and Rheological Measurements Kume et al. (2019)第15页，共25页。3-3. Information Retrieval in Individual MeasurementsFIG. Schematic of photoelastic modulation rheo-optical device. Optical elements in the alignment configurationCASE STUDY 1: Flow Dichroism and Birefring

20、ence of Polymers in Shear FlowsA Rheo-Optical Study of Shearing Thickening and Structure Formation in Polymer Solutions Kishbaugh and Muhugh (1993); Figs. Reproduced from Sondergaard and Lyngaae-Jorgensen (2019)第16页，共25页。Note that only data for the case of Mw=1.54 x 106 is shown in the following 3 p

21、agesOne-to-one correlationbetween the onset of shearthickening and the occurrenceof a maximum in the dichroism第17页，共25页。 The viscosity and dichroism patterns for the lowest concentration are similar to those exhibited by a lower molecular weight sample(Mw=4.3 x 105). Namely, the dichroism rises to a

22、 plateau, while viscosity undergoes a monotonicdrop with shear rate to an eventual Newtonian plateauViscosityDichroism At higher concentrations, a dramatic anddistinctive pattern emerges. One sees a shaperrise in the dichroism to an eventual maximum,while the viscosity simultaneously drops to aminim

23、um. This is followed by a region of shearthickening in which the viscosity continuouslyrises, while the dichroism decreases andeventually turns negative第18页，共25页。 This figure shows that, in this range, theorientation angle dropped to a constant near-alignment with the flow axis第19页，共25页。 Throughout

24、the entire flow curve,the birefringence exhibits a steadymonotonic increase with shear rate These data offer strong evidencethat the overall orientation of thechain segments is independent ofthe structuring processes, which maytake place as indicated in the dichroism第20页，共25页。CASE STUDY 2: Dynamics

25、of Multicomponent Polymer MeltsInfrared Dichroism Measurements of Molecular Relaxation in Binary Blend Melt Rheology Kornfield et al. (1989)3. The most interesting result is that the longest relaxation time of the the shorter chains is a strongly increasing function of the volume fraction of longer

26、chains. This contrasts with the predictions of the basic reptation model1. Chains are identical in chemical composition, but differ in M.W. Isotopic labeling with deuterium (D) can be used to distinguish one M.W. component from another2. At 2,180 cm-1 the C-D bond absorbs but the C-H bond does not第21页，共25页。CASE STUDY 3: Combined Rheo-Optical MeasurementsRheo-Optical Studies of Shear-Induced Structures in Semidilute Polystyrene Solutions Kume et al. (2019)1. Shear-induced structure formation in semidilute solutions of high molecular weight p