Figure 4. (A) OTR of
(TA@LDH/PEO)n (n =10-70) films with
different bilayer numbers; (B) Schematic diagram of gas penetration in a
barrier film.
The bare NR substrate displays an oxygen transmission rate (OTR) of 3190
cm3/(m2·24h·0.1MPa), as shown in
Figure 4A. Upon deposition of
(TA@LDH/PEO)ncoatings, the OTR values undergo a significant decrease. With an
increase in the number of the assembly layers, the permeability
decreases because of the barrier effect caused by horizontal LDH
nanosheets. The improved oxygen barrier properties are attributed to the
good 2D ordering of LDH nanosheets, which increases the diffusion path
of oxygen molecules, commonly known as tortuous pathway (Figure 4B). The
best oxygen resistance performance can be obtained when the composite
film has 50 layers (OTR = 110
cm3/(m2·24h·0.1MPa)). When the
number of (TA@LDH/PEO)n film layers continues to
increase, the oxygen barrier performance begins to decline. This is
probably because when there are too many layers and the film is too
thick, the substrate will be hard to bear so that the composite film
will fall out or crack. Therefore, 50 layers are selected as the best
number of bilayers.