A block copolymer

poly(ethylene oxide)-b-poly(N-acryloyl-L-proline methyl ester) short as D12-EA

was prepared via RAFT polymerization using macromolecular chain transfer agent containing dodecyl endgroup

whose structure was characterized by GPC and

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H NMR. The self-assembly of D12-EA in water and the reassembly behavior upon variation of temperature was explored via a combination of UV-Vis

dynamic light scatter (DLS)

static light scatter (SLS)

TEM

and temperature-variable

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H NMR. The D12-EA formed spherical micelle in water with radius about 20 nm when solution temperature was below the cloud point (CP) of thermo-sensitive poly (N-acryloyl-L-proline methyl ester) (A block). However

it reversibly transformed into vesicle with radius around 90 nm when solution temperature was above CP of A block. As revealed by

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H NMR spectra

the transition from sphere to vesicle was driven by the switch of A block form hydrophilic corona to hydrophobic core of micelle above CP to form aggregate with lower free energy.