Two dimensional infrared(2D-IR) spectroscopic studies of the viscoelastic behavior of liquid crystalline polyurethanes
| Autor: | Bindu R. Nair, Paula T. Hammond, Vasilis G. Gregoriou, Sheila Rodman |
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| Rok vydání: | 2002 |
| Předmět: |
chemistry.chemical_classification
Materials science Polymers and Plastics Infrared Organic Chemistry Relaxation (NMR) Infrared spectroscopy Polymer Condensed Matter Physics Viscoelasticity Condensed Matter::Soft Condensed Matter chemistry Chemical physics Polymer chemistry Materials Chemistry Perpendicular Side chain Deformation (engineering) |
| Zdroj: | Macromolecular Symposia. 184:183-192 |
| ISSN: | 1521-3900 1022-1360 |
| Popis: | Dynamic infrared dichroism techniques have been used to study a complex side chain liquid crystalline segmented polyurethane. The obtained dynamic spectra were analyzed using two dimensional infrared techniques (2D-IR) that allow the easier interperation of the dynamic response of this system. Side chain mesogens are monitored by the cyano tag at the end of the molecule while the hard segments can be viewed in the carbonyl spectral region. A study of the different parts of the macromolecule leads to an understanding of the elastic and the viscous orientation behavior of the polymer. We find that the elastic component of the strain aligns smectic layers parallel and hard domains perpendicular to the direction of strain. The viscous strain component, on the other hand, induces a perpendicular smectic layer and parallel hard domain orientation behavior. These observations are consistent with a model proposed in earlier work that the hard segments and the smectic layers change orientation as the applied strain is increased from low to high strains. In addition, we show further evidence for the coupling of the mechanical deformation behavior of the smectic layers and the hard domains and identified two primary relaxation times in this system. |
| Databáze: | OpenAIRE |
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