Presentation on theme: "Evgeny Karpushkin, Andrey Bogomolov WSC-9, Tomsk, Feb 2014"— Presentation transcript:
1 Evgeny Karpushkin, Andrey Bogomolov WSC-9, Tomsk, Feb 2014 Morphology assessment of polymer hydrogels using multivariate analysis of viscoelastic and swelling propertiesEvgeny Karpushkin, Andrey BogomolovWSC-9, Tomsk, Feb 2014
2 What is hydrogel? Large variety of gels, but in this talk gel = covalently cross-linked 3D (network) polymer swollen in waterProperties:hydrophilic, swollen, soft materialsbiocompatible or biodegradableresponsive to changes of temperature, pH and ionic strength; electrical and magnetic fieldsApplications:artificial implants (contact lens)supports for enzymes and cells immobilizationsensors, actuators, chemical valves and robotsmodels of tissues and organsfood industry, cosmetics, …
3 Examples of hydrogel morphology: polyHEMA 100 mmReactive & Functional Polymers62 (2005) 1–9Pores generation in HEMA gels:phase separation during polymerizationincorporation of soluble particlescryo (frozen solvent as porogen)liquid porogen (emulsion polymerization)introduction of gas generating substances100 mmJournal of Controlled Release102 (2005) 3–12400 mm100 mmSoft Matter 3 (2007) 1176–1184Macromolecules 40 (2007)1 mmBiomaterials 26 (2005) 1507–1514
4 Materials science: general aim Preparation conditionsUtilitarian propertiesStructure:porosity,topology,microphases,…Measured propertiesCompositionHow do preparation conditions influence the material structure?How does structure of material influence its functional properties?What material structure corresponds to certain measured properties?How to prepare a material with desired properties?
5 Remarks on microscopy Light microscope: rapid, good for start, but resolution not enoughElectron microscope:for dry samples structure is not always preservedElectron microscope:for swollen samples observed structure is highly dependent on conditionsdryswollenChamber pressure decreasing
7 Observed properties Morphology type Equilibrium swelling HomogeneousDropletsIn water, or DMSO, or aqueous NaClSometimes versus temperatureInterlockingFused particlesShear deformationMixedForced oscillatory deformationCreep (constant shear stress in time)
8 Morphology of hydrogels: diluent at preparation = water
9 Morphology of hydrogels: salting-in diluent at preparation 70/2(0.2M Mg(ClO4)2)70/2(0.05M Mg(ClO4)2)70/2(0.3M Mg(ClO4)2)70/2More diluent solvating power = less phase separation
10 Morphology of hydrogels: salting-out diluent at preparation 60/1(0.2M NaCl)60/1(0.4M NaCl)60/1(0.45M NaCl)60/1(0.475M NaCl)60/1(0.5M NaCl)60/1(0.525M NaCl)60/1(0.6M NaCl)60/1Less diluent solvating power = more phase separationFine tuning – never observed before!
17 PCA: 35 samples, 4 variables Equilibrium swelling, low frequency modulus, and pair of loss factorsThese variables are important as such, and therefore they are usually determined
18 Conclusions and perspectives PCA approach is promising for indirect morphology assessment.Fairly reliableFast and cheap as compared with the direct ESEMUses experimental variables are important as suchNeeds further investigationIs it possible to exclude swelling data?Creep curve fitting?Does the approach work with chemically different materials?
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