The effect of pressure on the microphase separation of diblock copolymer melts was investigated by dynamic density functional theory based on equation of state. The results correspond well with experiment data. With the application of high pressure, all of the phase regions corresponding to the different ordered morphologies become narrower. However, the pressure dependence of the order‐disorder transition temperature (TODT) relies on the symmetry of the diblock copolymer. In the very non‐symmetrical case when f is small, TODT decreases with increasing pressure, while in the symmetrical case when f = 0.5, TODT increases with increasing pressure. For the latter case, the increase in the total bead number of the system at the ODT is found, which is in good accordance with the experimental phenomenon that there is an increase in volume accompanying with the transition from ordered to disordered state. In contrast to the temperature, the pressure does not influence the starting time and the duration of microphase separation.
