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Reactive Mesogenes: Synthesis and Application in Optoelectronic Devices

Published online by Cambridge University Press:  15 March 2011

Peter Strohriegl ,
Doris Hanft ,
Markus Jandke  and
Thomas Pfeuffer
Peter Strohriegl
Affiliation:
Bayreuth University, Macromolecular Chemistry I and Bayreuth Institute of Macromolecular Research (BIMF), D-95440 Bayreuth, GERMANY, e-mail:, peter.strohriegl@uni-bayreuth.de
Doris Hanft
Affiliation:
Bayreuth University, Macromolecular Chemistry I and Bayreuth Institute of Macromolecular Research (BIMF), D-95440 Bayreuth, GERMANY, e-mail:, peter.strohriegl@uni-bayreuth.de
Markus Jandke
Affiliation:
Bayreuth University, Macromolecular Chemistry I and Bayreuth Institute of Macromolecular Research (BIMF), D-95440 Bayreuth, GERMANY, e-mail:, peter.strohriegl@uni-bayreuth.de
Thomas Pfeuffer
Affiliation:
Bayreuth University, Macromolecular Chemistry I and Bayreuth Institute of Macromolecular Research (BIMF), D-95440 Bayreuth, GERMANY, e-mail:, peter.strohriegl@uni-bayreuth.de
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Abstract

Reactive mesogenes posess polymerizable groups attached to a rigid, liquid crystalline core. From such molecules, densely crosslinked networks in which the liquid crystalline order is permanentely fixed can be formed by photopolymerization.

Our major synthetic goal was the formation of glass forming reactive mesogenes. Such compounds do not crystallize upon cooling but vitrify and form supercooled LC-phases ('LC-glasses'). They exhibit broad LC-phases and enable us to carry out photopolymerization in a broad range of temperatures.

We have systematically investigated how the topology of the reactive mesogenes influences the stability of the resulting glasses. Comparing twin molecules with three- and four-armed stars we found that the supercooled LC-phase in the three-armed stars has a stability superior to both twin molecules and four-armed stars. In the three-armed star Triple-4 with a suitable substituent pattern the supercooled LC-phase is stable at room temperature for at least nine months. Doped with suitable chiral molecules the glass forming nematics form cholesteric phases which were used for cholesteric polymer networks and for polarization holograms with one s-and one p-polarized writing beam.

Furthermore we have extended our synthetic efforts to reactive mesogenes with three or five conjugated fluorene units as LC-core. After orientation, the mesogenes were photocrosslinked and used as active layer in OLEDs that emit highly polarized blue light.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 709: Symposium CC – Advances in Liquid Crystalline Materials and Technologies , 2001 , CC3.2.1
Copyright
Copyright © Materials Research Society 2002

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