The precipitation polymerization of acrylamide/methacrylic acid (AAm/MMA) in ethanol (EtOH) was thoroughly investigated from detecting the homogeneity of the initial solution prior to polymerizations to the final products of the polymerizations. Dynamic light scattering and scanning electron microscopy were employed for the investigations. The solutions of AAm and AAm/acrylic acid (AAm/AA) were homogeneous. However, the solutions of AAm/MAA, AAm/poly(MAA) (PMAA), and AAm/ poly(AA) (PAA) were not homogeneous as they are usually considered to be: entities with size distributions of around 150, 40, and 17 ran, respectively, were detected at the polymerization temperature of 60 degreesC. Accordingly, analogous to the entities that are similar to the structure of micelles formed in the solutions of AAm/PMAA and AAm/PAA because of polymer-AAm interactions, it was suggested that the complexes of AAm/MAA stemming from the molecular interactions, particularly the (lypo-) hydrophobic interaction, aggregated to form minimonomer droplets at 60 degreesC. The monodisperse microspheres were prepared only in the AAm/MAA-EtOH systems, whereas the microspheres were not prepared in the homogeneous AAm-EtOH systems despite the precipitation of PAAm. The results obtained from various polymerizations showed that the microspheres originated from the polymerization within the minimonomer droplets. A new mechanism was established that describes the processes for the formation of all products possibly generated in the AAm-MAA-EtOH polymerization system. (C) 2004 Wiley Periodicals, Inc.