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Title: Charge Transport Properties of Reactive Calamitic Liquid Crystals
Author: Baldwin, Rodney James
ISNI:       0000 0001 3441 1439
Awarding Body: Queen Mary, University of London
Current Institution: Queen Mary, University of London
Date of Award: 2007
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Polymerisable liquid crystalline semiconductors, referred to as reactive mesogens (RMs), consist of rr-conjugated cores with reactive end groups decoupled by an aliphatic spacer. These can be polymerised within a mesophase, maintaining the self-assembled mesophase morphology and charge transport characteristics. By successfully maintaining desirable charge transport properties in polymerised films, these molecular systems can be used in organic electronic applications such as charge transport layers in organic light emitting diodes and field effect transistors. We present a systematic study in collaboration with Merck Chemicals Ltd (UK), of the effect of reactive end groups on charge transport in calamiti9' liquid crystals (RMs) using the time-of-flight (TOF) technique. Several different compounds were synthesised with a variation in both the LC mesogenic core group and the functional end groups. The introduction of reactive end groups in most cases affects the mesophase charge transport compared to the non-reactive LC mesophase transport. This manifests itself as a reduction in mobility, varying from a factor of four in the best case, to as large as two orders of magnitude. In the best systems studied, however, the reactive end group effect on the transport, compared to the nonreactive mesophase transport, is negligible. Polymerised reactive mesogens do maintain long-range transport, with comparable mobilities to those of the phase in which they were polymerised ·over a broad temperature range, including room temperature. The temperature independent hole and electron mobility found in polymerised systems is explored using the Holstein small polaron model in the nonadiabatic limit, yielding the relevant polaron binding energies and bandwidths. In addition to this the Bassler Gaussian Disorder Model is applied to the data yielding the relevant energetic disorder parameters.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available