期刊
ACS NANO
卷 5, 期 10, 页码 8019-8025出版社
AMER CHEMICAL SOC
DOI: 10.1021/nn2025644
关键词
graphene oxide; liquid crystal; nematic; assembly surface anchoring; folding; unfolding
类别
资金
- National Science Foundation through the Brown University MRSEC [DMR0520651, CMMI-1129703, CBET-1132446, DMR 0955612]
- China Scholarship Council (CSC)
- National Institute of Environmental Health Sciences [P42ES013660]
- Directorate For Engineering
- Div Of Civil, Mechanical, & Manufact Inn [1308396] Funding Source: National Science Foundation
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [0955612] Funding Source: National Science Foundation
Graphene oxide is promising as a plate-like giant molecular building block for the assembly of new carbon materials. Its water dispersibility, liquid crystallinity, and ease of reduction offer advantages over other carbon precursors if Its fundamental assembly rules can be Identified. This article shows that graphene oxide sheets of known lateral dimension form nematic liquid crystal phases with transition points in agreement with the Onsager hard-plate theory. The liquid crystal phases can be systematically ordered into defined supramolecular patterns using surface anchoring, complex fluid flow, and microconfinement. Graphene oxide is seen to exhibit homeotropic surface anchoring at interfaces driven by excluded volume entropy and by adsorption enthalpy associated with its partially hydrophobic basal planes. Surprisingly, some of the surface-ordered graphene oxide phases dry into graphene oxide solids that undergo a dramatic anisotropic swelling upon rehydration to recover their initial size and shape. This behavior is shown to be a unique hydration-responsive folding and unfolding transition. During drying, surface tension forces acting parallel to the layer planes cause a buckling in-stability that stores elastic energy In accordion-folded structures in the dry solid. Subsequent water infiltration reduces interlayer frictional forces and triggers release of the stored elastic energy in the form of dramatic unidirectional expansion. We explain the folding/unfolding phenomena by quantitative nanomechanics and introduce the potential of liquid crystal-derived graphene oxide phases as new stimuli-response materials.
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