Poly(ethylene glycol) methyl ether-block-poly(L-alanine)(MPEG-b-PA) was synthesized with the initiation of MPEGNH2.While MPEG is the hydrophilic block and PA is the hydrophobic block.It is known that poly(L-amino acid)s like polypeptides have their special secondary structures such asα-helix and β-sheet.1H-NMR and COSY-NMR were used to monitor the micellization process of a po ly(ethylene glycol) methyl etherblock-poly(L-alanine) copolymer (MPEG45-b-PA32).MPEG45-b-PA32 was dissolved in CF3COOD first

while poly(L-alanine) blocks were in random coil structure.When D2O was added in this CF3COOD solution

MPEG45-b-PA32 could selfassemble into micelles.In the micellization process

mobility of PA blocks decreased while MPEG blocks kept very high mobility.Based on the chemical shifts and COSY data analysis

it was concluded that poly(amino acid) tended trend to form α-helix structure from random coil while the copolymer assembled in water.At the same time

transmission electron microscopy (TEM) results revealed that the diblock copolymer formed spherical micelles with the size of 150～220 nm in an aqueous medium.