Fig. 3: Thermoresponsive polymer-based switchable catalytic systems.

a Positive thermoresponsive micellar nanoreactor—at lower temperature, the polymer is soluble in water and Aldol reaction is ‘off’ due to the absence of suitable environment (Inset: chemical structure of the polymer). At elevated temperature, micelle is formed and provided suitable environment for L-proline-catalyzed Aldol reaction. Adopted with permission from ref. ⁷², copyright 2013 American Chemical Society. b Negative thermoresponsive micellar nanoreactor—at lower temperature, formation of micelle allowed the substrates to access catalyst, whereas at higher temperature polymer chain collapsed to hydrophobic globules, which inhibit the formation of intermediate, resulting poor selectivity. Adopted with permission from ref. ⁸⁰, copyright 2021 American Chemical Society. c Self-regulating thermoresponsive catalyst surface—structure tips are coated with catalyst and upright/bent tips corresponding to ‘on/off’ catalysis. Below LCST of PNIPAAm, the catalyst tips enter the reagent layer, resulting an exothermic click reaction. Above the LCST, the PNIPAAm contracts and the structures bend, removing the catalyst from the reagent layer and turning ‘off’ the reaction. Adopted with permission from ref. ⁸², 2012, Nature Publishing Group, a division of Macmillan Publishers Limited.