Bidirectionally Modulating the Dissipative Phase Transition of UCST Polymers in a Programmable Manner Using Visible Light

Dynamic phase transitions are important in living organisms for sustaining their adaptive structures and functions. The design of artificial dynamic systems using light as a noninvasive input fuel has gained significant interest to mimic such adaptive features. Here the development of light-fueled dissipative phase transitions of upper critical solution temperature polymers by introducing pendant spiropyrans as photoactive units, is reported. The reversible open-close photoisomerization of spiropyrans is designed to undergo either an enhancement or a decline of their net charge, which is subsequently used to regulate the electrostatic interactions between polymer chains, and ultimately shift their phase transition temperatures to either a lower or a higher direction. The degree and speed of such bidirectional shifting are flexibly modulated by manipulating the external illumination parameters or varying the compositions/concentrations of the polymers. The diametrically opposite transmittance changes driven by light are utilized to produce a series of complementary patterns and shapes for application in transient information storage and encryption with improved accuracy and security. This work offers a bidirectional spatiotemporal modulation of dissipative phase transitions of polymers using visible light that allows highly tunable and adaptable features shared with their natural counterparts.