A non-equilibrium oscillatory starch derivative driven by thermally induced phase separation: Application in dynamic...

Smart materials typically exhibit instantaneous, reversible, and switch-like behaviors. However, their sensitive responses are dependent on external conditions, lacking temporal programmability. Herein, a timed response intelligent material with a multistage response mechanism is developed, which encompasses reversible, dormant, and irreversible response states. Temporal retardation and stimuli-selective activation are achieved via thermally induced oscillations. We report a time-programmable thermoresponsive material, thermally induced oscillatory starch derivative (TIOS), fabricated from 2-chloro-4,6-bis(diethylamino)-1,3,5-triazine and 2-hydroxy-3-isopropoxypropyl starch. When heated above its lower critical solution temperature (LCST), the TIOS undergoes phase separation to form hydrophobic aggregates. And upon cooling, it switches into a tunable dormant configuration featuring irreversible characteristics. After a controllable dormant duration, the material restores its bidirectional reversible responsiveness. At pH 0.7, the dormant period of TIOS is 25 min. Dormant periods and oscillatory behavior can be regulated by adjusting pH (0.5-0.8), salt concentration (NaCl or Na₂SO₄, 1 g/L-15 g/L), and mixed-solvent composition (10% ethanol or glycerol by volume). Furthermore, it can be regenerated and reused three times in high-temperature wastewater treatment, with a decolorization efficiency exceeding 95%. This study provides a feasible strategy for the design of smart materials with timed responses, and demonstrates its application potential in anti-counterfeiting and wastewater remediation.