Recent progress in photoreactive crosslinkers in polymer network materials toward advanced photocontrollability

Photochemically adaptable polymer materials, which change shape and physical properties under light irradiation, are widely used in the fields of medicine, electronics, and engineering due to their precise and remote processability. This processability is attributed to the photocleavage of chemical bonds introduced into the polymer materials. In particular, the efficient photolytic cleavage of the crosslinking points in the network induces rapid softening and degradation of the materials. Recently, diverse designs of light-responsive units have been developed to fabricate various photocontrollable materials with low-energy, rapid, and reversible photoreactivity. Furthermore, multiple stimuli-responsive materials have been demonstrated to control photodegradation reaction rates and photoreactivity by combining light with another stimulus, leading to advanced photocontrollable capabilities. This paper reviews the recent progress in developing photochemically adaptable polymer network materials by designing photoresponsive units, focusing on the chemical structures of cleavable moieties. Photochemically adaptable polymer materials are widely used in the fields of medicine, electronics, and engineering due to their precise and remote processability. Diverse designs of light-responsive units have been developed to fabricate various photocontrollable materials with low-energy, rapid, and reversible photoreactivity. Recently, multiple stimuli-responsive materials have been demonstrated to further control their photoreactivity by combining light with another stimulus, leading to advanced photocontrollable capabilities. This Focus Review summarizes the recent progress in developing photochemically adaptable polymer network materials by designing photoresponsive units, focusing on the chemical structures of cleavable moieties.