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pH-responsive ABA triblock copolymers PDEAEMA-b-PMPC-b-PDEAEMA were synthesized using atom transfer radical polymerization (ATRP) in methanol.The composition,structure,and molecular weight of the copolymer were characterized by FT-IR,1H-NMR and GPC,respectively.The pH sensitivity and micellization behavior of the synthesized triblock copolymers in aqueous solutions were investigated using UV transmittance measurements,fluorescence probe technique and transmission electron microscopy (TEM).The critical pH and the critical micelle concentration (CMC) of various triblock copolymers were determined by fluorescence measurements.Above the critical pH,the PDEAEMA-b-PMPC-b-PDEAEMA triblock copolymers formed aggregates of PDEAEMA as core and PMPC as shell.Under the critical pH,spontaneous disassociation of the core-shell aggregates occurred,and the hydrophobic PDEAEMA cores became hydrophilic chains.The TEM images showed that the size of the copolymer micelles was about 25-50 nm.