We show that glasses with aligned smectic liquid crystal-like order can be produced by physical vapor deposition of a molecule without any equilibrium liquid crystal phases. Smectic-like order in vapor-deposited films was characterized by wide-angle X-ray scattering. A surface equilibration mechanism predicts the highly smectic-like vapor-deposited structure to be a result of significant vertical anchoring at the surface of the equilibrium liquid, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy orientation analysis confirms this prediction. Understanding of the mechanism enables informed engineering of different levels of smectic order in vapor-deposited glasses to suit various applications. The preparation of a glass with orientational and translational order from a nonliquid crystal opens up an exciting paradigm for accessing extreme anisotropy in glassy solids.
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Flux melting of metal–organic frameworks
Recent demonstrations of melting in the metal–organic framework (MOF) family have created interest in the interfacial domain between inorganic glasses and amorphous organic polymers. The chemical and physical behaviour of porous hybrid liquids and glasses is of particular interest, though opportunities are limited by the inaccessible melting temperatures of many MOFs. Here, we show that the processing technique of flux melting, ‘borrowed’ from the inorganic domain, may be applied in order to melt ZIF-8, a material which does not possess an accessible liquid state in the pure form. Effectively, we employ the high-temperature liquid state of one MOF as a solvent for a secondary, non-melting MOF component. Differential scanning calorimetry, small- and wide-angle X-ray scattering, electron microscopy and X-ray total scattering techniques are used to show the flux melting of the crystalline component within the liquid. Gas adsorption and positron annihilation lifetime spectroscopy measurements show that this results in enhanced, accessible porosity to a range of guest molecules in the resultant flux melted MOF glass.
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- Award ID(s):
- 1661655
- NSF-PAR ID:
- 10138663
- Date Published:
- Journal Name:
- Chemical science
- Volume:
- 10
- Issue:
- 12
- ISSN:
- 2041-6520
- Page Range / eLocation ID:
- 3592 - 3601
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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