The reorientation of segments on the copolymer surface with change of immersion mediums have been investigated by dynamic contact angle (DCA) measurements. The samples are amphiphilic copolymer PS-b-PMAA or PS-b-PHPMA prepared by polymerized MAA or HPMA monomer with polystyrene macroinitiatior containing azo group. The results show that the reorientation of polar segments (PMAA or PHPMA segments) on the surface contribute to the contact angle hysteresis. The receding angle θr is very sensityve to polarity and mobility of the segments on copolymer surface while advancing angle θa remains at an approximate value for the samples on which surface PS segment enrichment took place

to the △θ

a differece between advancing angle and receding angle

can be used as an indication of reorientation ability of segments and/or groups on the copolymer surface.The values of advancing angle or of receding angle measured in the second immersion cycle are same as that in the first

respectively

this reveals that the reorientation of segments and/or groups are reversible with the environmental change in the case of both PS-b-PMAA and PS-b-OHOMA.The results also show that the contact angle hysteresis depend on temperature of medium

i.e.

the values of both θ and △θ decrease with increasing of temperature

and that dynamic behavior of the amphiphilic copolymers can be affect by ther ratio of sequence length(MPS/MPMAA/MPHPMA) in the macromolecular chain.