28 Photomechanical Effects in Crosslinked Liquid-Crystalline …
485
Fig. 28.4 (a) Photoinduced bending behaviour of a PAzo/PDDMA film upon irradition with UV
(10 mW cm -2 ) and visible (40 mW cm -2 ) light. (b) Bending angles as a function of irradition time
of UV light. Size of the films: 3 mm × 1 mm × 16 µm. (Reproduced from [34])
28.3 Reshaping of CLCPs Through the Rearrangement
of Network Structures
In application of photomobile polymer materials to actual devices such as soft actuators, CLCPs should be processable into adequate 3D shapes depending on their
uses. However, reshaping is a common challenge in crosslinked systems such as
elastomers, resins, and gels as they are insoluble and infusible. Especially, in the
preparation of CLCPs, conventional processes lead to the formation of flat films.
Therefore, construction of CLCPs with 3D structures has been particularly difficult. Leibler et al. developed a new class of polymer materials called vitrimers,
which are distinguished from conventional thermoplastics and thermosets [36–38].
Vitrimers are composed of crosslinked networks remoldable under heating through
exchange reactions such as transesterification. This strategy has also been applied
for thermoresponsive CLCPs based on epoxy networks [39].
485
Fig. 28.4 (a) Photoinduced bending behaviour of a PAzo/PDDMA film upon irradition with UV
(10 mW cm -2 ) and visible (40 mW cm -2 ) light. (b) Bending angles as a function of irradition time
of UV light. Size of the films: 3 mm × 1 mm × 16 µm. (Reproduced from [34])
28.3 Reshaping of CLCPs Through the Rearrangement
of Network Structures
In application of photomobile polymer materials to actual devices such as soft actuators, CLCPs should be processable into adequate 3D shapes depending on their
uses. However, reshaping is a common challenge in crosslinked systems such as
elastomers, resins, and gels as they are insoluble and infusible. Especially, in the
preparation of CLCPs, conventional processes lead to the formation of flat films.
Therefore, construction of CLCPs with 3D structures has been particularly difficult. Leibler et al. developed a new class of polymer materials called vitrimers,
which are distinguished from conventional thermoplastics and thermosets [36–38].
Vitrimers are composed of crosslinked networks remoldable under heating through
exchange reactions such as transesterification. This strategy has also been applied
for thermoresponsive CLCPs based on epoxy networks [39].