Poly(3-hexylthiophene)-block-poly(5,8-di-p-tolylquinoxaline-2,3-diyl) conjugated rod–rod copolymers: one pot synthesis, self-assembly and highly selective sensing of cobalt

Abstract

A family of well-defined poly(3-hexylthiophene)-b-poly(5,8-di-p-tolylquinoxaline-2,3-diyl) rod–rod block copolymers was designed and synthesized in one pot via mechanistically distinct, sequential living polymerization using Ni(dppp)Cl₂ as a single catalyst. The block copolymerization was demonstrated to proceed in a living/controlled chain-growth manner, affording the desired block copolymers in high yields with tunable compositions, controlled molecular weight, and narrow molecular weight distributions. The resulting block copolymer was revealed to self-assemble into various well-defined supramolecular structures depending on the solvents used such as nano-fibril and spherical nanoparticles. Very interestingly, such a block copolymer displayed highly selective visual detection for cobalt over most other competing metal ions by changing its orange color to light green and bright orange emission to deep green. The detection limit was estimated to be down to 1.0 × 10⁻⁷ M and the interference of the other competing metal ions is negligible. Furthermore, such a block copolymer can be applied using test strips, making it a practical, sensitive, and selective probe for cobalt ions.