Exploiting the full potential of layered materials for a broad range of applications requires delamination into functional nanosheets. Delamination via repulsive osmotic swelling is driven by thermodynamics and represents the most gentle route to obtain nematic liquid crystals consisting exclusively of single-layer nanosheets. This mechanism was, however, long limited to very few compounds, including 2:1-type clay minerals, layered titanates, or niobates. Despite the great potential of zeolites and their microporous layered counterparts, nanosheet production is challenging and troublesome, and published procedures implied the use of some shearing forces. Here, we present a scalable, eco-friendly, and utter delamination of the microporous layered silicate ilerite into single-layer nanosheets that extends repulsive delamination to the class of layered zeolites. As the sheet diameter is preserved, nematic suspensions with cofacial nanosheets of ≈9000 aspect ratio are obtained that can be cast into oriented films, e.g., for barrier applications.
Upcoming
efficient air-borne wind energy concepts and communication
technologies applying lighter-than-air platforms require high-performance
barrier coatings, which concomitantly and nonselectively block permeation
not only of helium but also of ozone and water vapor. Similarly, with
the emergence of green hydrogen economy, lightweight barrier materials
for storage and transport of this highly diffusive gas are very much
sought-after, particularly in aviation technology. Here the fabrication
of ultraperformance nanocomposite barrier liners by spray coating
lamellar liquid crystalline dispersions of high aspect ratio (∼20 000)
silicate nanosheets mixed with poly(vinyl alcohol) on a PET substrate
foil is presented. Lightweight nanocomposite liners with 50 wt % filler
content are obtained showing helium and hydrogen permeabilities as
low as 0.8 and 0.6 cm3 μm m–2 day–1 atm–1, respectively. This exhibits
an improvement up to a factor of 4 × 103 as compared
to high-barrier polymers such as ethylene vinyl alcohol copolymers.
Furthermore, ozone resistance, illustrated by oxygen permeability
measurements at elevated relative humidity (75% r.h.), and water vapor
resistance are demonstrated. Moreover, the technically benign processing
by spray coating will render this barrier technology easily transferable
to real lighter-than-air technologies or irregular- and concave-shaped
hydrogen tanks.
The fabrication of one-dimensional (1D) crystalline, monodomain nanocomposite films (hybrid Bragg stacks) is still limited to a few combinations of polymer and clay. The main reason is segregation of clay...
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