Civil Engineering Reference
In-Depth Information
macromolecules secreted by specii c cells [82-85]. Capadona
et al.
[81] have reinforced
ethylene oxide-epichlorohydrin 1:1 copolymer and poly(vinyl acetate) with NCCs. h e
resultant nanocomposites showed a reversible transition from a low stif ness (modulus
~ 20 MPa) state when swollen to a high stif ness (modulus ~ 800 MPa) state when dry
(see Figure 8.11). h is transition was reversible and attributed to the hydrogen bonds
between the NCCs, which can be tuned by addition of water, a hydrogen-bond-forming
solvent.
Figure 8.10
Tulip Queen of the Night petal gratings:
(a)
Picture of the Tulip Queen of the Night l ower.
(b)
h e SEM image shows the striated epidermis of the l ower; the periodicity is in the order of 2 μm
comparable to the one of the i lms.
(c)
Optical microscope rel ection image of the peeled epidermal layer
of the petal. h e transparent epidermal layer also maintains the regularity of the striation at er the peeling
process.
(d)
K-space imaging of the peeled epidermal layer showing iridescence. Please note that the scale
bar in (d) corresponds to 20 degrees [79]. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA,
Weinheim.
(
a
)
(
b
)
(
c
)
Interaction “on”
Interaction “of”
Figure 8.11
Stif ness modii cation of the
Cucumaria frondosa
(a sea cucumber) in the presence of
an external stimulus: the sea cucumber is in a relaxed state (A) and when touched the stif ness of the
dermis increases (B). In (C) is a schematic representation of the switching mechanism in the biomimetic
mechanically adaptive nanocomposites. In a swell state the interactions between the NCC are “switched
of,” while in a dry state the hydrogen bonds between NCC are “switched on” and a stif er material is
obtained [81] . Copyright © 2008 with permission from h e American Association for the Advancement
of Science.
