“Self-Lockable” Liquid Crystalline Diels–Alder Dynamic Network Actuators with Room Temperature Programmability and Solution Reprocessability

Article abstract of DOI:10.1002/anie.202000181

Novel main-chain liquid crystalline Diels—Alder dynamic networks (LCDANs) were prepared that exhibit unprecedented ease for actuator programming and reprocessing compared to existing liquid crystalline network (LCN) systems. Following cooling from 125 °C, LCDANs are deformed with aligned mesogens self-locked at room temperature by slowly formed Diels–Alder (DA) bonds, which allows for the formation of solid 3D actuators capable of reversible shape change, and strip walker and wheel-capable light-driven locomotion upon either thermally or optically induced order–disorder phase transition. Any actuator can readily be erased at 125 °C and reprogrammed into a new one under ambient conditions. Moreover, LCDANs can be processed directly from melt (for example, fiber drawing) and from solution (for example, casting tubular actuators), which cannot be achieved with LCNs using exchangeable covalent bonds. The combined attributes of LCDANs offer significant progress toward developing easily programmable/processable LCN actuators.

Full text of DOI:10.1002/anie.202000181

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
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Accepted Article
Title: “Self-Lockable” Liquid-Crystalline Diels-Alder Dynamic Network
Actuators with Room Temperature Programmability and Solution-
Reprocessability
Authors: Zhichao Jiang, Yaoyu Xiao, Lu Yin, Li Han, and Yue Zhao
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To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.202000181
Angew. Chem. 10.1002/ange.202000181
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10.1002/anie.202000181
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“Self-Lockable” Liquid-Crystalline Diels-Alder Dynamic Network
Actuators with Room Temperature Programmability and Solution-
Reprocessability
Zhi-Chao Jiang, Yao-Yu Xiao, Lu Yin, Li Han and Yue Zhao*
Abstract: Novel main-chain liquid crystalline polyesters were
designed and synthesized to demonstrate liquid crystalline Diels-
Alder dynamic networks (LCDANs) for soft actuator applications.
These materials exhibit unprecedented ease for actuator
programming and reprocessing compared to existing liquid
crystalline network (LCN) systems. Following cooling from around
125 oC, LCDANs can be deformed with aligned mesogens self-
locked at room temperature by slowly formed DA bonds, which
allows for the making of solid 3D actuators capable of reversible
shape transformation, and strip walker and wheel capable of light-
driven locomotion upon either thermally or optically induced order-
disorder phase transition. Any actuator can readily be erased at 125
oC and reprogrammed into a new one under ambient conditions.
Moreover, LCDANs can be processed directly from melt (e.g. fiber
drawing) and, being dissolvable in solution, from solution as well (e.g.
casting tubular actuators), which cannot be achieved with liquid
crystalline dynamic networks using exchangeable covalent bonds
(vitrimers). The combined attributes of LCDANs are a significant
progress toward developing easily programmable/processable LCN
actuators.
address these issues, liquid crystal vitrimers have first been
developed using exchangeable ester bonds to replace traditional
permanent covalent bonds in LCNs.[8] Through the
transesterification reaction, the network topology can be
rearranged, which makes it possible to reprogram the shape of
the actuator or reprocess it at high temperatures (>130 oC).
Subsequently, a variety of reactions promoting exchangeable
covalent bonds have been applied in making LCN actuators,
such as transcarbamoylation,[10] boronic-ester exchange
reaction,[11] and photo-exchange reactions of disulfide[12] and
allyl sulfide,[13] all of which allow an actuator to be reshaped
under external force at high temperature or under illumination.
Herein, we report the design and study of a new material system
for LCN actuators, namely, liquid crystalline Diels-Alder dynamic
networks (LCDANs), which elevates the ease for actuator
programming and reprocessing to a new height. The thermally
reversible nature of some Diels-Alder reactions has long been
utilized for designing recyclable and reprocessable thermoset
polymers.[14] Typically, the material network consisting of
diene/dienophile adducts is heated to high temperature (usually
above 110 °C) to trigger the reverse Diels-Alder reaction (retro-
DA) so that it can reach melt state for reprocessing, while the
DA bonds reform to restore the network structure on cooling.[15]
Although the kinetics and mild reaction conditions of DA bonds
appear suitable for LCN actuators, it has not been explored for
LCNs to our knowledge. One design consideration is that the
material needs to possess an LC (order) to isotropic (disorder)
phase transition temperature significantly lower than the
dissociation temperatures of the DA bonds, so that the material
can be reversibly actuated through back-and-forth phase
transition without disrupting the DA bonded network. In this
study, we synthesized two LCDANs differing in the mesogenic
moiety in the polymer structure. They show unprecedented ease
of programmability and reprocessability, which greatly facilitates
the making of LCN actuators. More specifically, following a
simple thermal treatment for DA bond dissociation, all necessary
steps for an actuator fabrication can be accomplished at room
temperature: an LCDAN specimen is deformed or processed
into a specific 3D shape and the alignment of mesogens in
deformed state is self-locked by a slowly formed DA-bonded
network, without the need for any photo- or thermal polymer
crosslinking. Such LCDAN actuators display reversible shape
change upon heating above and cooling below the order-
disorder phase transition, and can also be made into a light-
fueled walker or wheel. Moreover, unlike liquid crystalline
vitrimers using exchangeable covalent bonds, the recycling and
reprocessing of LCDANs can be realized not only from melt but
also from solution as they can be dissolved in solvent with
thermally dissociated DA bonds.
Polymer soft actuators have aroused great scientific interest for
use as stimuli-controlled shape changing and moving devices for
soft robots,[1] micromechanical systems,[2] artificial muscle[3] and
energy generators.[4] Liquid crystal polymer networks including
elastomers (LCNs) possess both entropy elasticity of polymer
networks and anisotropic property arising from ordered
mesogens, which makes them stand out among the many
polymeric materials for soft actuator applications.[5] LCN
actuators are typically fabricated by firstly orienting the
mesogens through mechanical stretching or surface alignment,
and subsequently locking the ordered structure through a chain
crosslinking reaction.[6] Upon reversible order-disorder phase
transition of the mesogens, LCNs can exhibit macroscopic and
reversible shape change. Although substantial progress has
been made in the development of LCN actuators in terms of
actuation performance in the past decade,[7] their large-scale
applications are still hampered by the demanding actuator
fabrication and the lack of ease for processing. First, most LCN
actuators require photo-crosslinking or photo-initiated reaction
during the preparation process.[8] Due to the limited penetration
of light, LCN actuators can only be prepared into thin films for
the sake of complete crosslinking. Secondly, like thermosetting
polymers and elastomers, LCNs cannot be melted or dissolved
in soliton for reprocessing due to crosslinked polymer chains. To
[*]
Z. Jiang, Y. Xiao, Lu Yin, Li Han, Prof. Dr. Y. Zhao
Departement de chimie, Universite de Sherbrooke
Sherbrooke, Quebec, J1K 2R1 (Canada)
E-mail: yue.zhao@usherbrooke.ca
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
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LCDAN to have plenty of time to be programmed by mechanical
force into a desired shape with oriented mesogens at room
temperature. With the reformation of DA bonds over time, the
alignment of mesogens and the programmed shape can be self-
locked. Without any post-treatment, the obtained monodomain
LCDAN actuator can realize reversible contraction and
elongation upon order-disorder phase transition. Due to the
dynamic nature of DA bonds, the actuation behavior can be
erased by heating to 125 oC and the LCDAN sample can be
reprogrammed into new actuators with different shapes and
actuation behaviors.
Figure 1. Design of the “self-lockable” liquid crystalline Diels-Alder dynamic
network (LCDAN) actuators: a) Chemical structures of two main-chain liquid
crystalline polymers (LCPs) bearing furan side groups and containing either
biphenyl or azobenzene as mesogenic moieties, as well as the preparation of
their LCDANs through DA bonded-crosslinking in the presence of
bismaleimide; and b) Schematic showing the room temperature programming
and self-locking of LCDAN actuators capable of reversible shape change upon
the LC-isotropic (order-disorder) phase transition.
Figure 1a shows the chemical structures of two main-chain liquid
crystalline polymers (LCPs) and their use for preparing LCDANs.
We designed and synthesized two polyesters bearing a number
of furan side groups for DA bonds and containing either biphenyl
or azobenzene mesogenic moieties in all monomeric units,
denoted as BP-LCP and AZO-LCP, respectively (synthesis and
characterization are detailed in Supporting Information). To
prepare their LCDANs, either of the polymers dissolved in
tetrahydrofuran was mixed with stoichiometric quantity of
bismaleimide (BM) and cast into a Teflon mold. After removing
the solvent, an LCDAN with DA bonds as crosslinking points
was obtained. Using mechanical stretching as an example of
shape programming, Figure 1b schematically illustrates the
deformation of LCDAN and self-locking of oriented mesogens by
DA bonds at room temperature with no need for a separate
crosslinking reaction. After heating for dissociation of DA bonds
through retro-DA reaction, the LCDAN sample is cooled to room
temperature. Since the generated furan and maleimide groups
after thermal dissociation need time to react with each other and
reform DA bonded network,[16] the slow kinetics allows the
Figure 2. a) and b) DSC heating and cooling scans for AZO-LCDAN and
AZO-LCP, and BP-LCDAN and BP-LCP, respectively. The inset is a magnified
region showing a broad endothermic peak on heating the LCDANs. c) Tensile
test curves of AZO-LCDAN cooled from 125 oC to room temperature for
different times prior to the measurement. d) Change in the infrared
absorbance of out of plane vibration of −C=C−H in maleimide over different
waiting time at room temperature, recorded from a thin film of AZO-LCDAN
cooled from 125 oC to room temperature. e) Photos of an AZO-LCDAN strip
actuator displaying reversible contraction (in isotropic phase) and elongation
(at room temperature) as well as data showing the stable actuation upon ten
heating/cooling cycles. f) Two dimensional XRD patterns of AZO-LCDAN
actuator (top) and BP-LCDAN actuator (bottom) recorded in the isotropic
phase and after cooling to room temperature (the arrow indicates the
stretching direction)
The formation of DA bonds in both BP-LCDAN and AZO-LCDAN
was firstly revealed by the swelling experiment. In contrast to the
soluble LCPs bearing furan side groups (without addition of BM),
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the LCDANs can only swell in chloroform at room temperature
formed DA-bonded network. Such programed actuators of both
LCDANs exhibit similar thermal actuation behaviors: contracting
upon heating into the isotropic phase (e.g. 80 oC) and extending
after cooling back to room temperature, with a reversible
actuation degree (RAD) around 48% for AZO-LCDAN and 45%
for BP-LCDAN (an AZO-LCDAN strip and the definition of RAD
are shown in Figure 2e). The reversible shape change remains
stable upon repeated heating-cooling cycles (Figure 2e). The
reversible shape change arises from the transition between
uniaxially oriented and disordered mesogens as confirmed by X-
Ray Diffraction (XRD) measurements (Figure 2f, Figure S13-
S14). For both LCDAN actuators, at 25 oC (extension),
mesogens are aligned along the strain direction as can be seen
from the wide-angle reflection arcs at 2θ≈20o (nematic order)
and small-angle reflection at 2θ≈2.5o (ordered smectic layers). In
the isotropic phase, the orientation of mesogens disappears.
Moreover, experiments revealed the effects of a number of
parameters on the actuation performance of the LCDANs. First,
to have a stable RAD over repeated heating-cooling cycles, the
temperature in the isotropic phase should be below about 100
oC to retain a stable DA-bonded network; heating to higher
temperatures leads to DA bonds dissociation and, consequently,
declined reversible actuation (Figure S15). Secondly, after
stretching an actuator at room temperature, it should be kept
under deformation for over 5h to obtain a well crosslinked
network due to the slow DA bond formation kinetics. If needed,
this waiting time can be reduced considerably by heating slightly
after 24h (Figure S9). Figure
2 presents a series of
characterization results of LCDANs and their actuators, showing
particularly the slow formation of DA bonds that opens the
window for room temperature programming and self-locked
network structure for reversible shape changes. First, comparing
the two linear LCPs with their corresponding LCDANs, the
differential scanning calorimetry (DSC) measurements show that
the formation of DA bonds has little effect on the glass transition
temperature (Tg) appeared at about 25 oC, but reduces
significantly the LC-isotropic phase temperature, TLC-iso, by some
o
20 oC, to 73 C (on heating) for AZO-LCDAN (Figure 2a) and 67
oC for BP-LCDAN (Figure 2b). The lowered TLC-iso in DA-bonded
actuator is a sought-for feature, because a large gap between
TLC-iso and the temperature promoting effective DA network
disruption is necessary for repeated shape change of the
LCDAN actuator upon the order-disorder phase transition while
retaining a stable DA-bonded network. From the DSC heating
curves, DA bonds dissociation appears to occur over
a
o
temperature range of about 110-150 C, as revealed by a broad
endothermic peak for both LCDANs. Interestingly, after cooling
to room temperature, the dissociated furan/maleimide groups in
LCDANs reform DA bonds slowly at room temperature. This is
demonstrated by the tensile tests shown in Figure 2c. A series of
AZO-LCDAN films were heated at 125 oC for 3 min to dissociate
DA bonds, followed by cooling to room temperature. Afterwards,
the samples were subjected to the tensile test after various
o
o
times at room temperature (about 26 C). As can be seen, the
the actuator under strain (e.g. 40 C) to speed up the formation
LCDAN sample becomes increasingly harder with increasing the
time at room temperature prior to the test. Similar results were
obtained for BP-LCDAN (Figure S10). Indeed, both Young’s
modulus and yield stress for the two LCDANs increase
significantly by prolonging the waiting time at room temperature,
especially over the first 5h (Figure S11). This observation
indicates that the number of DA bonds formed at room
temperature increases over time, because Young’s modulus and
yield stress generally increase with increasing density of DA
crosslinks.[18] The slow reformation of DA bonds at room
temperature was further confirmed by recording the infrared
spectra of a thin AZO-LCDAN film after cooling from 125 oC
(Figure 2d). The intensity of the imide absorption band at 700
cm-1, attributed to the out of plane vibration of −C=C−H in
maleimide,[19] decreases over time, implying the continuous
formation of DA bonds. This slow kinetics of DA reaction makes
it possible to program LCDAN actuators with desired shapes at
room temperature. As the LCDAN is deformed with aligning
mesogens, the forming DA bonds builds up a network structure
that self-locks the programmed shape and enables the
reversible shape change as long as the DA-bonded network
remains.
of DA bonds (Figure S16). Thirdly, following the thermal
treatment at 125 oC, if wanted, the LCDAN actuator can be
stretched at higher temperatures before cooling to room
temperature. While a similar RAD (around 54%) was observed
when the LCDAN was stretched in the LC phase, stretching in
the isotropic phase resulted in a decreased RAD (about 30%
when stretched at 120 oC, Figure S17). This effect is likely
explained by a less efficient orientation of mesogens upon
stretching in the isotropic phase.
The attributes of shape programming and self-locking at room
temperature leading to reversible actuation greatly enhance the
achievable shape morphing complexity and flexibility, as well as
shape change-enabled motion of the LCDAN actuators.
Examples are given in Figure 3 to illustrate the unique properties
of LCDANs. First, after cooling from 125 oC, an AZO-LCDAN
strip was directly twisted around
a metal bar at room
temperature, followed by awaiting the fixation of the mesogen
alignment and helical shape through gradually formed DA
crosslinks. As the temperature goes above TLC-iso, the helix
unwinds and the strip recovers the flat shape; while on cooling
back to the LC phase, the helical shape reappears (Figure S19
and Movie S1). Secondly, since both the alignment of mesogens
o
Before showcasing the exceptional room temperature shape
programmability and easy reprocessability from either melt or
solution of the LCDAN actuators, we used the simple uniaxial
stretching to investigate their actuation properties and the
and DA crosslinks in LCDAN are lost at 125 C, the previously
programmed shape is erased (Figure S15) and the same
sample can be reprogrammed into different shapes and
endowed with diverse reversible actuation modes. As shown by
the example in Figure 3a and Movie S2, a flat AZO-LCDAN
sheet was firstly programmed into the dome-shaped actuator.
Upon heating and cooling, the actuator undergoes reversible
dome-flat shape transformation. Then, the actuator was heated
o
influencing factors. After 3 min at 125 C followed by cooling, a
strip of either AZO-LCDAN or BP-LCDAN was stretched at room
temperature to 300% strain and remained under strain for
certain time to ensure the self-locking of aligned mesogens by
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at 125 oC to eliminate the previous network, the cooled and
refreshed sheet was then reprogramed to have two reversed
pyramids. Using the same procedure, the actuator could be
continually reprogramed, in an on-demand manner, to various
types of pyramids or dooms. For each architecture, it can be
flattened on heating above TLC-iso and reappeared on cooling
below TLC-iso. Moreover, as demonstrated in Figure 3b and Movie
S3, using a single sheet of BP-LCDAN, a series of 3D origami
structures, including accordion fold, Miura-Ori fold, Origami
spiral and Origami tent, were obtained, which can unfold and
refold repeatedly on heating/cooling cycles. These origami
transformers were easily prepared at room temperature thanks
to the properties of the LCDANs. Owing to the stability of
reversible actuation during the reprograming process (Figure
S20), the number of reprogrammable shapes is infinite in
principle. More interestingly, the self-locking LCDAN can be
further used to fabricate reprogrammable solid 3D actuator,
which can hardly be achieved using other LCN materials.
Examples are given in Figure 3c and Movie S4. The cuboid of
BP-LCDAN after retro-DA reaction can be shaped to a sphere
manually like a playdough at room temperature. After self-
locking, the sphere exhibits reversible ball-cuboid transformation
by heating and cooling through TLC-iso. The same sample can
then be reprogrammed into other solid 3D geometries such as
star, pie and parallelepiped, through simple thermal erasure
followed by room temperature processing. One mention about
the Movies should be made: the apparently slow actuation
speed is due to the used slow rate of temperature change.
asymmetric change in curvature makes the wheel’s center of
gravity shifting from right to left, which results in rolling of the
wheel away from the light beam at an average speed of 19.4
cm/min. It should be emphasized that all the examples of
reversible shape change and light-driven locomotion were
realized using the LCDAN actuators programmed and self-
locked at room temperature, which is a first-time achievement.
Not limited to actuation by direct heating/cooling, AZO-LCDAN
based actuators can also achieve light-fueled shape change and
locomotion, because the rod-like azobenzene mesogens in the
stable trans isomer are converted to the bent cis isomer upon
absorption of UV light (365 nm), while the latter returns to the
trans state by absorption of visible light (550 nm) (Figure S21).
Since azobenzene mesogens upon the reversible trans–cis
isomerization can lead to reversible order-disorder phase
transition, the bending-unbending actuation behavior can be
observed with uniaxially aligned monodomain AZO-LCDAN strip
actuator upon alternating UV and visible light irradiation (Figure
S22). Moreover, when a monodomain AZO-LCDAN strip is
laminated with a flexible polyimide film (Kapton), the bilayer
actuator can present reversible bending and unbending by
turning on/off UV light (320-480 nm, Figure S23 and discussion).
Since the actuator can be easily programmed into a desired
shape or structure, versatile light-controlled motions can be
realized. On the one hand, a bilayer strip was shaped into
caterpillar-inspired arching walker (Figure 3d, Figure S24 and
Movie S5). When UV light is on, the strip arches up due to
contraction of the bottom LCDAN layer, while when the light is
turned off, the strip flattens to restore the initial shape. With the
two ends adjusted purposely for unbalanced friction with the
substrate surface, the walker can crawl forward upon repeated
UV light on/off cycles, at an average speed of 3.4 cm/min. On
the other hand, the bilayer actuator was programmed into a
light-fueled rotating wheel (Figure 3e and Movie S6). Upon UV
light irradiation, the curvature of illuminated right side decreases
as a result of bending towards the outer AZO-LCDAN layer,
while the unexposed left side remains unchanged. This
Figure 3. Schematic illustrations and photographs of various room
temperature programmed and self-locked LCDAN actuators: a) On-demand
reprogramming of 3D structures of a single AZO-LCDAN sheet actuator
(1cm*1cm*0.15mm in size, see Movie S2 showing reversible 3D-flat
transformation). b) Different 3D origami architectures programmed from one
planar BP-LCDAN actuator (1cm*1cm*0.15mm in size, see Movie S3 for
reversible flat-origami transformation). c) Reversible 3D-to-3D solid shape
conversion based on a bulk BP-LCDAN actuator (3mm*3mm*2.6mm in size,
see Movie S4 for reversible 3D-to-3D transformation). d) An AZO-
LCDAN/Kapton bilayer actuator capable of crawling forward upon UV light
on/off cycles (see Movie S5). e) An AZO-LCDAN/Kapton bilayer wheel
executing rolling motion under UV light irradiation (see Movie S6).
Finally, both BP-LCDAN and AZO-LCDAN display unmatched
ease for recycling and reprocessing. Unlike insoluble vitrimers
using exchangeable bonds, the LCDANs can be dissolved in
organic solvents and processed from solution. This is
demonstrated by the preparation of a tubular actuator in Figure
4a and Figures S25-S26. Fragments of BP-LCDAN were
dissolved in chloroform at 120 oC in an enclosed pressure vessel
filled with N2 gas; when cooled to room temperature, the solution
remained clear for at least 2h. By casting the solution into the
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space between two concentric cylinders, followed by drying and
uniaxial stretching, a tubular actuator with thermally induced
reversible expanding-shrinking capability was obtained (Figure
4a and Movie S7). Moreover, the LCDANs not only can be
remolded under hot-compression like vitrimers (Figure S27),
they can also be easily reprocessed from melt. Figure 4b and
Figures S28-S29 show LCDAN fiber actuators easily prepared
In summary, we have designed and synthesized two main-chain
liquid crystalline polyesters that form Diels-Alder bond-based
liquid crystalline dynamic networks. These LCDANs can be
shaped or programmed into 3D structured actuators (such as
helix, origami and various 3D solid shapes) at room temperature
and, surprisingly, self-locked by slowly formed DA bonds for
reversible shape transformation, with no need for additional
thermally or optically initiated chain crosslinking. If wanted, the
DA network formation can be speeded up by slight heating (to
about 40 oC). Using oriented AZO-LCDAN strip laminated with a
polyimide film (Kapton), UV light-driven caterpillar-like crawling
and wheel rotating locomotion can be realized. Furthermore,
unlike liquid crystalline vitrimers that generally can only be
reshaped or molded by high temperature compressing, the
LCDANs can be dissolved in a hot solvent and, after cooling to
room temperature, can be solution-processed as demonstrated
by the tubular actuator. They can also be processed from the
melt. Actuating fibers can be obtained by directly drawing a
viscous melt followed by cooling, twisting the fibers together
leads to actuating yarns. As compared to existing LCN materials,
our LCDANs offer exceptional ease for constructing a stimuli-
controlled shape morphing or moving actuator. Indeed, the
combined attributes, including room temperature programming
and self-locking of aligned mesogens, easy erasure for
reprogramming or recycling, and processing from solution or
melt, make them a new promising material system for LCN
based polymer actuator development and applications.
o
by dipping the tips of a tweezer into the viscous melt (>155 C)
and rapidly drawing it. During the stretching process, the fibers
are cooled down in air and the aligned mesogens are locked by
DA bond crosslinks over time. As shown, the BP-LCDAN fibers
exhibit thermally induced reversible straight-random coil
actuation (see Movie S8). Such actuating LCDAN fibers are a
potential candidate for smart textile applications. For example, a
thin BP-LCDAN yarn (3.5 mg, about 56 mm in length and 0.16
mm in diameter) prepared by twisting four fibers, can easily lift
up a clamp (2986.3 mg, 850 times heavier than the yarn’s own
weight) by 18 mm upon heating (Figure 4b and Movie S9).
Acknowledgements
Y. Zhao acknowledges financial support from the Natural
Sciences and Engineering Research Council of Canada
(NSERC) and le Fonds de recherche du Quebec: Nature et
technologies (FRQNT). Z. Jiang thanks FRQNT for awarding
him a scholarship. Z. Jiang, Y. Xiao, L. Yin and L. Han thank the
China Scholarship Council (CSC) for awarding them
scholarship.
a
Conflict of interest
The authors declare no conflict of interest.
Keywords: liquid crystal polymer actuators
• Diels-Alder
dynamic networks • room temperature programming • solution-
reprocessability • light-driven soft robots
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10.1002/anie.202000181
Angewandte Chemie International Edition
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Zhi-Chao Jiang, Yao-Yu Xiao, Lu Yin,
Li Han and Yue Zhao*
Liquid crystalline dynamic networks
can be shaped into 3D objects at room
temperature while being stabilized by
slowly formed Diels-Alder bonded
crosslinks. The actuators can execute
thermally or optically induced
Page No. – Page No.
“
Self-Lockable” Liquid-Crystalline
Diels-Alder Dynamic Network
Actuators with Room Temperature
Programmability and Solution-
Reprocessability
reversible shape change for doing a
mechanical work or locomotion.
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