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Phase biaxility in smectic-a side-chain liquid crystalline elastomers
Rebekka Storz1, Ansgar Komp, Anke Hoffmann
1Institut für Makromolekulare Chemie, Stefan-Meier-Str. 31, 79104 Freiburg, Germany.
Macromolecular Rapid Communications
|June 28, 2011
Summary
Nuclear magnetic resonance (NMR) investigations reveal biaxial phase behavior in liquid crystalline side-chain elastomers. Network dynamics near the glass transition appear to drive the formation of this biaxial phase.
Area of Science:
- Materials Science
- Polymer Chemistry
- Liquid Crystals
Background:
- Smectic-A liquid crystalline side-chain elastomers exhibit complex phase behaviors.
- Understanding biaxiality in these materials is crucial for advanced applications.
Purpose of the Study:
- To investigate the biaxial phase behavior of smectic-A liquid crystalline side-chain elastomers.
- To determine the molecular origins and driving forces of biaxiality.
Main Methods:
- Utilized Deuterium (2H) Nuclear Magnetic Resonance (NMR) spectroscopy.
- Measured quadrupolar splitting of benzene-d(6) and hexamethylbenzene-d(18) spin probes.
- Analyzed angular dependence of spectral data relative to the magnetic field.
Main Results:
- Observed biaxiality in two distinct side-chain elastomers with varying mesogen geometries.
- The angular dependence of quadrupolar splitting required an asymmetric term for fitting biaxial systems.
- Biaxiality was consistently observed as the elastomers approached their glass transition temperature.
Conclusions:
- The formation of the biaxial phase in these elastomers is strongly influenced by network dynamics.
- Molecular geometry of the mesogens plays a role in the observed biaxiality.
- Network dynamics appear to dominate biaxial phase formation near the glass transition.
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