In order to understand the coarsening of microdomains in symmetric diblock copolymers at the late stage

a model for block copolymers is proposed.By incorporating the self consistent field theory with the free energy approach Lattice Boltzmann model

hydrodynamic interactions can be considered.Compared with models based on Ginzburg-Landau free energy

this model does not employ phenomenological free energies to describe systems.The model is verified by comparing the simulation results obtained using this method with those of a dynamical version of the self consistent mean field theory.After that

the growth exponents of the characteristic domain size for symmetric block copolymers at late stage are studied.It is found that the viscosity of the system affects the growth exponents greatly

although the growth exponents are all less than 1/3.Furthermore

the relations between the growth exponent

the interaction parameter and the chain length are studied.The rescaled simulation results show that the dependence of growth exponent on the interaction parameter is trivial; however

the length of the polymer chain may lead to the change of the growth exponent.This conclusion is different from that based on a free energy function given by the Ginzburg Landau expression.This difference may come from the additional correlation considered in the self consistent field theory of our model.Nevertheless

the chain length effect on the growth exponent is little compared with that of the fluid viscosity.