Multi-responsive behavior of highly water-soluble poly(3-hexylthiophene)-block-poly(phenyl isocyanide) block copolymers

Abstract

The design and synthesis of highly water-soluble conjugated block copolymers with multi-responsive properties are of great interest due to the copolymers’ potential as solution processable semiconductor materials. Herein, we report a one-pot synthesis of well-defined block copolymers containing conjugated poly(3-hexylthiophene) (P3HT) and poly(phenyl isocyanide) (PPI) bearing hydrophilic tri(ethylene glycol) monomethyl ether chains. These block copolymers have good solubility in water and exhibit excellent thermoresponsive behavior. The lower critical solution temperature (LCST) in water can be facilely tuned through varying the concentration or polymer composition. Moreover, the optical properties of the block copolymer are dependent on the solvents used owing to the distinct self-assembled structures. In CHCl₃, the P3HT-b-PPI block copolymer exhibits pH-responsive behavior with the emission color changing between orange and blue upon alternate additions of trifluoroacetic acid and triethylamine. In addition, such block copolymers are revealed to be good materials for live cell imaging.