Liquid crystalline vitimers (LC-vitrimers) can be easily processed into complex three-dimensional configurations. In this paper, we present a photo-responsive LC-vitrimer by simply introducing a photo-thermal agent aniline trimer into the LC-vitrimer system. As aniline trimer acts as a curing agent, it can be homogeneously dispersed in the material, avoiding aggregation which commonly happens to nano-fillers. As a result, the resultant polymer not only can perform three light-controlled functions (welding, healing and shape memory), but also can be prepared into aligned monodomain LC actuators with strains of about 40%–45%.Download high-res image (114KB)Download full-size imageThe ACAT-LC-vitrimer not only can perform three light-controlled functions (welding, healing and shape memory), but also can be prepared into aligned monodomain LC actuators with strains of about 40%–45% by simply stretching the cured material at temperature above the topology-freezing transition temperature.

Shape memory polymers (SMPs) have been widely used in our daily life (e.g. shrinkable tubes) and are expected to play more important roles in soft robotics, biomedical devices and other high-tech areas. Due to the energy shortage the world is facing now, it would be ideal to convert normal heat-driven SMPs into sunlight-responsive SMPs, so that solar energy could be converted into mechanical work. It is even more desirable to make SMPs flexibly switch between photo-responsiveness and photo-inertness. However, these objectives have not been realised so far. Here, we come up with a straightforward and low-cost method to do so by coating thermal-responsive SMPs with CH3NH3PbI3 perovskite. We find that CH3NH3PbI3 has excellent photo-thermal effect. As it can effectively convert solar energy into heat, the shape change of SMPs can be controlled by sunlight. The CH3NH3PbI3 layer can be easily washed off with water. The coating–erasing can be repeated many times to make the SMPs photo-responsive and photo-inert alternatively. The concept introduced here will not only expand the application of many currently available thermal-responsive SMPs, but also provide a practical method to make good use of solar energy.

Smart polymers have been playing indispensable roles in our lives. However, it is challenging to combine more than three stimuli-responses or functionalities into one polymer, not to mention integrating multi-stimuli responsivity and multi-functionality at the same time. Vitrimers, an emerging type of materials, are covalently crosslinked networks that can be reprocessed but are still infusible and insoluble. Herein, we show that simply introducing oligoaniline into a vitrimer results in a covalently crosslinked material that can respond to six different stimuli (heat, light, pH, voltage, metal ions and redox chemicals) and perform six functions (shape memory, welding, healing, recycling, electro-chromism and adsorption of metal ions). New properties, which cannot be found in either neat vitrimers or oligoanilines, are generated, including photo-heal-ability, photo-weldability, pH-induced shape memory, enhancement of the photo-thermal effect due to metal ions absorption and simultaneous multi-tasking operations. Furthermore, the material is low-cost and suitable for large-scale mass production.

Achieving 3D structures that can be reversibly formed from dry 2D polymer films is useful for the development of suitable smart materials capable of converting an external stimulus into a mechanical response. For the construction of dynamic 3D structures, carbon nanotubes dispersed in liquid crystalline vitrimers constitute so far one of the few available materials that can show robust reconfiguration, easy repair, and low-temperature resistance. However, the severe aggregation of carbon nanotubes causes defects in the materials formed and incurs additional costs. Here, we show that organic polydopamine (PDA) nanoparticles can well replace carbon nanotubes to make suitable liquid crystalline vitrimers for the construction of dynamic 3D structures. We were able to disperse the PDA nanoparticles homogenously into the polymer matrix without carrying out any surface modification and without using any dispersant or sonication, which are required procedures for dispersing almost all inorganic nanoparticles into a polymer matrix. Moreover, the mechanical properties of the liquid crystalline vitrimer were found to be greatly improved. Using this composite, we also showed here a new method to achieve light-controlled 3D deformation into static structures.

Making dynamic three-dimensional (3D) structures capable of reversible shape changes or locomotion purely out of dry polymers is very difficult. Meanwhile, no previous dynamic 3D structures can be remade into new configurations while being resilient to mechanical damages and low temperature. Here, we show that light-activated transesterification in carbon nanotube dispersed liquid crystalline vitrimers enables flexible design and easy building of dynamic 3D structures out of flat films upon irradiation of light without screws, glues, or molds. Shining light also enables dynamic 3D structures to be quickly modified on demand, restored from distortion, repaired if broken, in situ healed when microcrack appears, assembled for more sophisticated structures, reconfigured, and recycled after use. Furthermore, the fabrication, reconfiguration, actuation, reparation, and assembly as well as healing can be performed even at extremely low temperatures (e.g., −130 °C).

Photo-active shape memory polymers (SMPs) are considered as a promising candidate for converting light into mechanical energy. However, most known SMPs are only thermo-responsive. To achieve photo-activity, photo-responsive choromophores or fillers usually have to be incorporated from the very beginning of the material synthesis. Here, we introduce a novel post-synthesis approach to endow normal SMPs with photo-active properties using mussel-inspired surface chemistry. Without changing the original properties, the resultant polydopamine (PDA) coated SMPs show an efficient photo-active performance. The coating can be easily patterned and erased, which allows flexible light-triggered 3-D shape deformation of a planar SMP sheet. Moreover, owing to the high chemical activity, the PDA coating also provides a platform to optimize the surface properties of the photo-responsive SMPs through secondary surface modification.

Assembling epoxy, one of the most common and widely used thermosets, by welding with remote control is extremely difficult and has not been realized so far, as epoxy cannot melt or be dissolved. Here we present a very simple but highly efficient solution by exploring the photothermal effect of carbon nanotubes (CNTs) to manipulate the transesterification reaction in vitrimers. The carbon nanotube dispersed vitrimer epoxy presented here can be welded by light within seconds or minutes. Moreover, various CNT–vitrimer epoxy materials with different chemical compositions and physical properties can be joined together. Furthermore, transmission welding can be used to weld CNT–vitrimers with other kinds of epoxy or thermoplastic polymers, which is not applicable to welding by direct heating and impossible to realize using the currently available photoweldable covalently cross-linked polymer networks. Additionally, these networks can be efficiently healed by light without the involvement of any glue or sealing agents.

Assembling epoxy, one of the most common and widely used thermosets, by welding with remote control is extremely difficult and has not been realized so far, as epoxy cannot melt or be dissolved. Here we present a very simple but highly efficient solution by exploring the photothermal effect of carbon nanotubes (CNTs) to manipulate the transesterification reaction in vitrimers. The carbon nanotube dispersed vitrimer epoxy presented here can be welded by light within seconds or minutes. Moreover, various CNT–vitrimer epoxy materials with different chemical compositions and physical properties can be joined together. Furthermore, transmission welding can be used to weld CNT–vitrimers with other kinds of epoxy or thermoplastic polymers, which is not applicable to welding by direct heating and impossible to realize using the currently available photoweldable covalently cross-linked polymer networks. Additionally, these networks can be efficiently healed by light without the involvement of any glue or sealing agents.

Smart polymers have been playing indispensable roles in our lives. However, it is challenging to combine more than three stimuli-responses or functionalities into one polymer, not to mention integrating multi-stimuli responsivity and multi-functionality at the same time. Vitrimers, an emerging type of materials, are covalently crosslinked networks that can be reprocessed but are still infusible and insoluble. Herein, we show that simply introducing oligoaniline into a vitrimer results in a covalently crosslinked material that can respond to six different stimuli (heat, light, pH, voltage, metal ions and redox chemicals) and perform six functions (shape memory, welding, healing, recycling, electro-chromism and adsorption of metal ions). New properties, which cannot be found in either neat vitrimers or oligoanilines, are generated, including photo-heal-ability, photo-weldability, pH-induced shape memory, enhancement of the photo-thermal effect due to metal ions absorption and simultaneous multi-tasking operations. Furthermore, the material is low-cost and suitable for large-scale mass production.

Shape memory polymers (SMPs) have been widely used in our daily life (e.g. shrinkable tubes) and are expected to play more important roles in soft robotics, biomedical devices and other high-tech areas. Due to the energy shortage the world is facing now, it would be ideal to convert normal heat-driven SMPs into sunlight-responsive SMPs, so that solar energy could be converted into mechanical work. It is even more desirable to make SMPs flexibly switch between photo-responsiveness and photo-inertness. However, these objectives have not been realised so far. Here, we come up with a straightforward and low-cost method to do so by coating thermal-responsive SMPs with CH3NH3PbI3 perovskite. We find that CH3NH3PbI3 has excellent photo-thermal effect. As it can effectively convert solar energy into heat, the shape change of SMPs can be controlled by sunlight. The CH3NH3PbI3 layer can be easily washed off with water. The coating–erasing can be repeated many times to make the SMPs photo-responsive and photo-inert alternatively. The concept introduced here will not only expand the application of many currently available thermal-responsive SMPs, but also provide a practical method to make good use of solar energy.

Achieving 3D structures that can be reversibly formed from dry 2D polymer films is useful for the development of suitable smart materials capable of converting an external stimulus into a mechanical response. For the construction of dynamic 3D structures, carbon nanotubes dispersed in liquid crystalline vitrimers constitute so far one of the few available materials that can show robust reconfiguration, easy repair, and low-temperature resistance. However, the severe aggregation of carbon nanotubes causes defects in the materials formed and incurs additional costs. Here, we show that organic polydopamine (PDA) nanoparticles can well replace carbon nanotubes to make suitable liquid crystalline vitrimers for the construction of dynamic 3D structures. We were able to disperse the PDA nanoparticles homogenously into the polymer matrix without carrying out any surface modification and without using any dispersant or sonication, which are required procedures for dispersing almost all inorganic nanoparticles into a polymer matrix. Moreover, the mechanical properties of the liquid crystalline vitrimer were found to be greatly improved. Using this composite, we also showed here a new method to achieve light-controlled 3D deformation into static structures.

Photo-active shape memory polymers (SMPs) are considered as a promising candidate for converting light into mechanical energy. However, most known SMPs are only thermo-responsive. To achieve photo-activity, photo-responsive choromophores or fillers usually have to be incorporated from the very beginning of the material synthesis. Here, we introduce a novel post-synthesis approach to endow normal SMPs with photo-active properties using mussel-inspired surface chemistry. Without changing the original properties, the resultant polydopamine (PDA) coated SMPs show an efficient photo-active performance. The coating can be easily patterned and erased, which allows flexible light-triggered 3-D shape deformation of a planar SMP sheet. Moreover, owing to the high chemical activity, the PDA coating also provides a platform to optimize the surface properties of the photo-responsive SMPs through secondary surface modification.