Synthesis and characterization of ph sensitive core-shell-corona micelles of poly(styrene-block-2-vinylpyridine-block-ethylene oxide) ABC triblock copolymer in aqueous solutions

The coreshellcorona forming ABC triblock copolymer poly(styrene-block-2- vinylpyridine-block-ethylene oxide), PSP2VPPEO, was synthesized using reversible addition fragmentation chain transfer (RAFT) radical polymerization and characterized by NMR and GPC as PS₁₃P2VP₆₂PEO ₄₇. The aggregation behavior in aqueous solution as a function of pH and temperature was studied. Turbidity measurements were used to monitor the effects associated with change in pH. The pH-sensitive P2VP block (insoluble above pH >5) and resultant protonation/deprotonation phenomenon plays decisive role in the aggregation. We found that spherical micelles of considerably low aggregation number form at pH >5. SANS and DLS characterization indicate the micelles' size and spherical shape remained virtually constant in the pH range 1 to 5. The size and shape were further confirmed by cryo-TEM.