Pitch Measurements on Chirally Doped Ferroelectric Nematics
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Nanotechnology (MPNAT), MSc
Publicerad
2023
Författare
Jonsson, Patrick
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Following the recent discovery of the ferronematic liquid crystal phase, it is important to explore the material’s properties as well as to devise methods of identification. In this report, an experimental method to measure the helical pitch of
the ferronematic material RM734 doped with a chiral dopant S811 by use of the
so-called circularly rubbed cell method is explored for the first time and compared
to other methods. The method utilises a cell of two substrates linearly and circularly rubbed of which the pitch is measured from the resulting deviation angle
of disclination lines induced by this particular geometry. The results showed that
the pitch in the polar ferroelectric phase behaved similarly to that of the non-polar
nematic phase but with a small change in magnitude at the phase transition to the
polar phase. Phase transition temperatures could also be determined and a negative
trend between the doping concentrations and transition temperatures for both the
isotropic to nematic and nematic to ferronematic phases was observed. Finally, a
first attempt was made at in-situ ultraviolet light-induced polymer stabilisation of
the ferronematic liquid crystal by use of photoreactive monomers mixed into the
liquid crystal. This attempt yielded inconclusive results as polymer stabilisation
was not observed, yet there seemed to be some adverse effects on the liquid crystal.
Beskrivning
Ämne/nyckelord
pitch, ferronematic, liquid crystal, circular alignment