Design of stimuli-responsive nanoparticles with optoelectronic cores by post-assembly cross-linking and self-assembly of functionalized block copolymers

Abstract

Temperature- and pH-sensitive nanoparticles having optoelectronic cores were synthesized by post-assembly cross-linking reaction of a block copolymer composed of poly(N-vinyl amine) and poly(N-isopropylacrylamide), which was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. The self-assembly of the block copolymer in a selective solvent, followed by the site-selective cross-linking of poly(vinyl amine) segment with anthracene and thiophene dialdehydes, afforded stable and uniform core cross-linked nanoparticles having pH-sensitive imine linkages. As comparisons, the poly(vinyl amine) segment in the block copolymer was modified selectively with monoaldehyde derivatives to yield anthracene- and thiophene-functionalized block copolymers, which can form self-assembled micelles with optoelectronic cores in aqueous solutions. Temperature-dependent morphological changes and optical properties of the core cross-linked nanoparticles and the functionalized block copolymers were compared in selective and non-selective solvents, which were characterized by DLS, UV–vis, fluorescence, and CV measurements. The core cross-linked nanoparticles also exhibited pH-triggered disintegration. To the best of our knowledge, this is the first report on the comparison of two series of stimuli-responsive nanoparticles, in which the optoelectronic cores are formed by post-assembly cross-linking reaction with the dialdehyde derivatives and self-assembly of the functionalized block copolymers prepared with the monoaldehyde derivatives.