3.5 Shape Memory Hydrogels
Shape memory polymers (SMPs) are stimuli-responsive materials that can change
shape when exposed to an external stimulus [109]. The most common type of shape
memory material is one for which the shape change is achieved by changes in
temperature, i.e., a thermally induced shape memory effect. Such materials have a
permanent shape, but they can be reshaped above a critical, switching temperature
and fixed into a temporary shape when cooled under stress to below the switching
Fig. 26 Origins of the
non-freezing (nf) water as a
function of FOSM
concentration in HFmx
hydrogels: total nf water
(black circle); nf water due
to hydrogen bonding (red
circle); and nf water due to
nano-confinement (blue
circle). The datum point at
[FOSM] ¼ 0 represents the
average value for
crosslinked HEA hydrogels
with different crosslink
densities
(C s,XLHEA ¼ 19.9 Æ 1.8 wt
%) Reproduced from Ref.
[25] with permission
Fig. 27 Fraction of
nonfreezing water in HFmx
hydrogels as a function of
interdomain spacing
determined from SANS.
Reproduced with
permission from Ref. [25]
200
B. D. Vogt and R. A. Weiss