Photoregulative phase change biomaterials showing thermodynamic and mchanical stabilities.

Azobenzenes are great photochromic molecules for switching the physical properties of various materials via trans - cis isomerization. However, the UV light resulted cis -azobenzene is metastable and thermodynamically gets back to trans -azobenzene after ceasing UV irradiation, which causes an unwanted property change of azobenzene-containing materials. Additionally, thermal and mechanical conditions would accelerate this process dramatically. In this present work, a new type of azobenzene-containing surfactant is designed for the fabrication of photoresponsive phase change biomaterials. With a "locked" cis -azobenzene conformation, the resulting biomaterials could maintain their disordered state after ceasing UV light, which exhibit great resistance to thermal and piezo conditions. Interestingly, the "locked" cis -azobenzene could be unlocked by Vis light in high efficiency, which opens a new way for the design of phase change materials only responding to light. By showing stable cis -azobenzene maintained physical state, the newly fabricated biomaterials provide new potential for the construction of advanced materials, like self-healing materials, with less use of long time UV irradiation for maintaining their disordered states.