ABSTRACT: We describe the enhanced mechanophore activation within nanosized core-shell micelles, which also present temperature and ultraviolet (UV) light-responsive properties. The model micelle was fabricated by the self-assembly of an amphiphilic block copolymer of poly(tert-butyl acrylate-b-N-isopropylacrylamide) with one spiropyran (SP) moiety at the midpoint of chain [SP-(t-BA88-b-NIPAM62)2, P2]. Micellization of P2 in tetrahydrofuran (THF)/water mixed solvent enhanced the reactivity of the electrocyclic ringopening reaction of SP to merocyanine (MC) isomer under sonication because micellization caused SP-centered PtBA block entangled and partially swelled in the micellar core and the increase of the dielectric constant of the medium around the SP, which could facilitate the conversion of SP to MC. This new enhanced mechanophore activation model demonstrated here is valuable as a probe to detect stress activation within nanosized particles and to design multiple-responsive materials.

Macromolecules 2016, 49, 98-104