The temporal change of complex viscosity (eta(*)) of two plates consisting of an end-functional monocarboxylated polystyrene (PS-mCOOH) and poly(methyl methacrylates) (PMMA) with various amounts of poly(methyl methacrylate-ran-glycidyl methacrylate) (PMMA-GMA) was measured by a rotational rheometer. There were three distinct stages for the change of eta(*) with time: (i) stage I, where eta(*) increased rapidly at short times and approached a steady value at later times; (ii) stage II, where eta(*) did not change; and (iii) stage III, where eta(*) increased slowly again and reached a final value. The apparent reaction kinetics obtained from the results in stage I was a first-order reaction. The change of the interfacial roughness between two plates with reaction time was investigated by transmission electron microscopy and atomic force microscopy after selective removal of unreacted PS-mCOOH layer. At long reaction times, the interface became pinched off, and then microemulsions (and micelles) were formed in the PMMA phase.