Synthesis of poly(N-isopropylacrylamide)-b-poly(2-vinylpyridine) block copolymers via RAFT polymerization and micellization behavior in aqueous solution

Poly(N-isopropylacrylamide)-b-poly(2-vinylpyridine) (PNIPAM-b-P2VP) block copolymers were synthesized for the first time via reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of S-1-dodecyl-S^′-(a, a^′-dimethyl-a^″-acetic acid)trithiocarbonate as chain transfer agent (CTA) and 2, 2^′-azobis(isobutyronitrile) as initiator. Both pH- and thermo-induced micellization behavior of the PNIPAM₅₉-b-P2VP₁₀₂ block copolymer in dilute aqueous solution was investigated by pyrene fluorescence, dynamic and static light scattering, transmission electron microscopy and ¹H NMR. The results show that the critical aggregation pH value of the block copolymer is around 5 and the critical aggregation temperature of the block copolymer is around 42 °C. A reversible transition between P2VP-core and PNIPAM-core micelles can be observed through an intermediate unimer state in aqueous solution.