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Title: "Janus" liquid crystals based on diphenylacetylene
Author: Ma, Tiantian
Awarding Body: University of York
Current Institution: University of York
Date of Award: 2013
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Supermolecular architecture has the ability to control the fine property and location of specific functional groups which allows them to be applied in various advanced fields. One of the most intriguing aspects is the self-organisation of complex giant molecular systems, especially for the materials with diversely functionalised faces or sides, which can recognise from one side to another, also known as "Janus" materials. In this project, dendritic supermolecules with more than one type of LC at the periphery (Janus liquid crystals) were developed. These LC molecules have a rigid diphenylacetylene core to which the dendritic linking scaffolds for the periphery groups can be attached. With different LC phase inducing ability, both the end-on and side-on mesogenic units have been used to build the amphiphilic system. The polyphilic materials containing different types of aliphatic chains as end-groups, which can enhance microphase segregation in this family. Two types (1:3 and 3:3) of Janus liquid crystals with different ratios of peripheral moieties were synthesized, along with their liquid crystal properties being studied. The mesomorphic behaviour of the Janus LCs is determined by the type of the mesogenic units, the microphase segregation effect controlled by the aliphatic chains, and also the steric effect relevant to the central core and dendritic scaffold. The synergy and competition among these factors generated mesophase behaviours which are unique to this type of supermolecular LC system. A series of side-on functionalized monomeric mesogens, LC dimers and trimers, and LC multipedes which is the intermediate in the synthesis of Janus LCs, were all developed as contrasts to the Janus LCs, for the systematical study in the mesomorphic behavior. Several of the giant molecular LCs based on hexaphenylbenzenes were also obtained from the Janus LC and oligomers via alkyne trimerization. With the unusual molecular conformation and distribution of peripheral groups, they also have novel self-assembling behaviours. Along with the Janus LCs, the supermolecular LCs provided an elegant entry for understanding the connection between the nanoscale structure and the macroscopic physical properties.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available