We simulate the microphase separation dynamics of aqueous solutions of the triblock polymer surfactants (ethylene oxide)(13)(propylene oxide)(30)(ethylene oxide)(13) and (propylene oxide)(19)(ethylene oxide)(33)(propylene oxide)(19) by a dynamic variant of mean-field density functional theory for Gaussian chains. This is the first 3D mesoscale model for the dynamic behavior of specific complex polymer solutions. Different mesoscale structures (micellar, hexagonal, bicontinuous, and lamellar and dispersed coexisting phases) are formed depending on composition. The numerical results are in good agreement with experiment. The intermediate hexagonal and bicontinuous phases of(ethylene oxide)(13)(propylene oxide)(30)(ethylene oxide)(13) solution retain a rich defect structure. Concentrated solution (60%) of (propylene oxide)(30)(ethylene oxide)(33)(propylene oxide)(19) shows the onset of macrophase separation, with small water droplets dispersed throughout the system. We confirm the experimental observation that the lamellar phase formation does not depend on the block sequence. Quenched from homogeneous state, the kinetics of each system consists of a fast local aggregation stage and subsequent slow rearrangement by defect annihilation. We conclude that the simulation method is a valuable tool for description of 3D morphology formation in a wide variety of complex polymer liquids.