We present a reactive dynamic mean-field density functional method that gives insight in pathway controlled morphology formation in irreversibly reacting polymer systems that undergo simultaneous micro- and/or macrophase separation. Taking reactive blending as an example for simulations, we show that this type of polymer processing is very effective in emulsifying incompatible polymers and that reactions are essential in obtaining a regularly emulsified blend. Moreover, we show that a rationally designed processing pathway that includes shearing, reactions, and microphase separation can lead to layered structures, and we propose a physical mechanism for this phenomenon