期刊
MOLECULAR PHYSICS
卷 113, 期 17-18, 页码 2776-2790出版社
TAYLOR & FRANCIS LTD
DOI: 10.1080/00268976.2014.996617
关键词
nano graphene; hexabenzocoronene; liquid crystal; molecular dynamics
资金
- European Union (European Social Fund - ESF)
- Greek national funds through Operational Programme 'Education and Lifelong Learning' of National Strategic Reference Framework (NSRF) - Research Funding Programme: THALIS
- Investing in knowledge society through European social fund [MIS 379436]
- IKY Fellowships of Excellence for Postgraduate Studies in Greece - Siemens Programme [11126/13a]
Discotic polyaromatic molecules, similar to nanometric graphene flakes, constitute an interesting class of materials for organic electronic applications. Grafting flexible side chains around the periphery of such molecules enhances their processability and gives rise to diverse behaviours, such as the manifestation of liquid-crystalline character and anisotropic mechanical response. In this work, we examine by means of molecular dynamics simulations the properties of molecular crystals comprised of alkyl-substituted hexa-peri-hexabenzocoronene mesogens. Pristine and mono-substituted systems by hydrogen or iodine atoms are modelled, with variable side chain length. A general structural and mechanical robustness to peripheral substitution is reported, with the mesogens forming tightly packed molecular wires even at elevated temperature and pressure. In their discotic ordering, the molecules present relatively low translational mobility, a beneficial phenomenon for charge transport. A thermotropic dependence of the mechanical response is identified, with the systems behaving differently in their room-temperature crystalline phase and in their liquid-crystalline phase at elevated temperatures. The melting process is also examined, elucidating an initial negative expansion along a high symmetry direction and the existence of a metastable state, before falling into the final liquid-crystalline state.
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