Microphase transition of triblock copolymer styrene - butadiene - styrene (SBS )was studied by rheometrics mechanical spherometer. The transition temperature was certain according to the rheological behavior differences during the transition. For the first time

microphase dissolution was investigated and the phase dissolution was found to proceed through four distinct stages. In the second and forth stage

G' eαt η' eβt

where G' and η' are dynamic modulus and dynamicviscosity reactively

t is the phase dissolution time

a.βare different for different stages and different dissolution temperature. In the framework of Dickie

consider-ing the molecule diffusion and the fluid mechanics reaction under shear condition

the rheological behavior in four stages was analysed and explained

the interiority of rheological properties dependence on time during phase dissolution was mani-fested primitively.