Aqueous solution free-radical copolymerization of acrylamide with hydrophobic butyl acrylate (BA) was performed by potassium persulfate as an initiator in the presence of nanoclay. The effect of two nanoclays with different natures, i.e. hydrophilic Cloisite Na⁺ and hydrophobic Cloisite 30B, on the microstructure and aqueous solution viscosity of the synthesized copolymers were studied. It was found from microstructural studies by NMR that copolymerization with Cloisite Na⁺ may proceed via a mechanism similar to the heterogeneous mechanism, while those with Cloisite 30B may proceed simultaneously with both micellar and heterogeneous mechanisms with a relatively high tendency toward the micellar method. These findings were further confirmed by the water solubility, XRD, TEM, dynamic light scattering (DLS) and viscosity analyses. Significant intercalation of the chains into the clay galleries was observed only with Cloisite Na⁺. The results of the DLS analysis as well as the aqueous solution viscosity versus copolymer composition, NaCl concentration and temperature revealed intermolecular aggregation of the BA groups especially for multiblock structured copolymers synthesized with an emulsifier or Cloisite 30B.