Synthesis and chemosensory properties of terpyridine-containing diblock polycarbazole through RAFT polymerization

This paper describes the synthesis of a terpyridine-containing diblock copolymer, poly(N-vinylcarbazole)-block-poly[4′-((4-vinylphenyl) phenyl)-2,2′:6′,2″- terpyridine] (poly(VK₁₅-b-TPY₄)), using the macro-chain transfer agent VK macro-CTA, and employing two-step reverse addition-fragmentation transfer (RAFT) polymerization. We examined the effect of terpyridine units on sensory characteristics of fluorescent chemosensors. VK macro-CTA and diblock copolymer poly(VK₁₅-b-TPY₄) both exhibited moderate thermal stability, with thermal decomposition temperatures of 5% weight losses at approximately 307°C and 378°C, respectively, suggesting that the enhancement of thermal stability was attributed to the incorporation of terpyridine segments into the block copolymer. Poly(VK₁₅-b-TPY₄) exhibited higher sensitivities to Ni^{2 +} and Mn^{2 +} ions, with Stern-Volmer constants (K_sv) of 2.58 × 10⁵ M^{- 1} and 2.57 × 10⁵ M^{- 1}, respectively. Adding a Zn^{2 +} ion not only caused partial fluorescence enhancement (3.2-fold quantum efficiency) but also induced a bathochromic shift of emission peak by approximately 56 nm (from 429 nm to 485 nm), indicating that the Zn^{2 +}-terpyridine complex reduced the twist and vibration of the C-C polymer backbone and enhanced the charge transfer from donors to acceptors because of the more planar and rigid structure. Our results suggest that poly(VK₁₅-b-TPY₄) is a promising material for chemosensory applications.