Temperature-Dependent Shape and Morphology Transformation of Colloidal Particles by Controlled Assembly of Thermoresponsive Polymers

Recently, colloidal particles that exhibit real-time tailored properties in response to external stimulus have recently been in the spotlight due to their diverse range of applications. Herein, we developed a simple and practical method for producing colloidal particle with temperature-driven transformation of shape and morphology via temperature-dependent assembly of polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) and poly(N-isopropylacryamide) (PNIPAM) in a chloroform-in-water emulsion. Depending on the surrounding temperature, convex lens-shaped particle and pupa-like particle can be prepared by precise positioning of PNIPAM. At the lower temperature than LCST of PNIPAM, PNIPAM was dissolved from chloroform to water, producing convex lens-shaped particles with vertical cylinders. In contrast, the PNIPAM was localized preferentially in the P4VP domains in chloroform when the temperature is higher than LCST of PNIPAM, producing pupa-like particles with axially stacked lamellar. Importantly, we successfully demonstrated reversible transformation between anisotropic shapes of BCP particles using solvent-adsorption annealing method, suggesting a great promise for use in sensor, detector, and drug delivery applications.