Self-assembly and pH-Responsive Behavior of Poly(4-hydroxystyrene)–b-Poly(N-vinylamine) Diblock Copolymer Synthesized by RAFT Polymerization
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Poly(N-vinylamine) (PVAm) is an interesting polymer having a large amount of primary amine groups, but controlled radical polymerization of this monomer has been reported rarely. We synthesize poly(4-hydroxystyrene)–b-poly(N-vinylamine) (PHS-b-PVAm) by Reversible Addition Fragmentation Chain-Transfer (RAFT) polymerization. We use ‘switchable’ RAFT agent to make poly(4-acetoxystyrene)-b-poly(N-vinylformamide) (PAcOS-b-PNVF), a precursor of PHS-b-PVAm. The reactivity of C-S double bond on the switchable RAFT agent can be controlled by protonation and deprotonation of pyridinyl Z group which gives a proper control for the polymerization of both PAcOS and PNVF blocks. Hydrolysis of PAcOS-b-PNVF produces a diblock copolymer of PHS-b-PVAm, which has an acidic phonolic moeity on the hydroxystyrene block and a basic primary amine group on the vinylamine block. The diblock polymer undergoes self-assembly in water, forming a spherical nanoparticle.