Visible Light Initiated Thermoresponsive Aqueous Dispersion Polymerization-Induced Self-Assembly

We report an updated polymerization-induced thermal self-assembly (PITSA) [Figg, C. A.; et al. Chem. Sci . 2015, 6, 1230]. The concept is validated using visible light initiated RAFT aqueous dispersion polymerization of diacetone acrylamide monomer at 25 – 70 °C. This PITSA formulation produces block copolymer lamellae at 25 °C while the copolymer morphology evolves from spheres to worms to vesicles during polymerization at 60 °C, which is above the lower critical solution chain length (LCSCL) of the core-forming block. Particle shape and size uniformity can be controlled by reaction temperature using a single photo-PISA formulation. Vesicles-to-lamellae and vesicles-to-worms transitions are achieved in situ upon cooling reaction dispersions (70 °C) to 25 °C, leading to the transformation of initially free-flowing liquids to physical hydrogels. Moreover, reversible thermoresponsive lamellae-to-vesicles-to-lamellae and worms-to-vesicles-to-worms transitions of as-synthesized nanoparticles are achieved in dilution in a heating–cooling cycle. This thermoresponsive photo-PISA formulation updates Figg’s PITSA protocol mainly in three aspects: (1) the absence of LCST limitation, (2) user-friendly control of particle shape and size uniformity by reaction temperature using a single photo-PISA formulation, and (3) reversible thermoresponsive transition of the ketone-functionalized vesicles to customer-guided lamellae or worms.