Multiple Responsiveness of Polymer Actuators

To improve photosensitivity of polymer materials, an effective protocol is to increase the content of photosensitive moieties. However, most of photosensitive units are toxic. The high content is not acceptable for real-world applications. Therefore, achieving photosensitive polymers with low content of photosensitive moieties but maintaining their photosensitivity remains a challenge. Herein, a protocol is reported to address this challenge by combining photosensitive monomers with hygroscopic monomers, where the synergistic action of two types of functional moieties can improve the photosensitivity of polymer network. Upon exposure to light irradiation, the polymer can be driven by not only the structural isomerization of photosensitive units, but also the photothermal effects. This synergistic effect results in the polymer-based soft actuators capable of showing rapid response to light even at the extremely-low content of photosensitive moieties of 2.6 mol.%. Importantly, the combination of hygroscopic and photosensitive moieties provides polymer with multiple responsiveness including acidochromism, humidity responsiveness, photohardening, shape memory, photochromism, and in situ swelling, making it useful in sensing systems, information transmission, and artificial muscles.