Development of reversibly light-responsive BCP particle by introducing photo-responsive surfactants

Abstract

Microparticles having reversible shape-tunable properties have benn[been] recieved[received] a lot of interest for enlarging the field of smart materials. Herein, we develop block copolymer (BCP) particles having reversibly transformable shape by the wavelength-selective light irradiation. The key factor that attain the reversible shape transition of particles is to invent a spiropyran-based surfactant (Spiropyran-DTAB), which can have ring-opening and ring-closing photoisomerization by exposing the UV (365nm) or visible light, respectively. The photoisomerization of Spiropyran-DTAB tunes the interfacial tension and wetting properties of BCPs in response to light of a set wavelength, resulting the wavelength-dependent appearance and inner structure of BCP particles. With UV light exposure, onion-shaped BCP particles having hydrophilic outermost layer are generated, while ellipsoidal-shaped BCP particles having axially stacked morphology are produced by visible light irradiation. Finally, we sucessfully[successfully] demonstrate that the feature of BCP particles can be transformed reversibly between the sphere-shaped particles and anisotropic (i.e., ellipsoid or convex-lens) particles depending on the wavelength of light, indicating the strength and effectiveness of spiropyran surfactants.