Two latex interpenetrating polymer networks (LIPNs) were synthesized with meth methacrylate (MMA) and octyl acrylate (OA) as monomers, respectively. The apparent kinetics of polymerization for the LIPNs was studied. This demonstrates that network II does not have a nucleus formation stage. The monomers of network II were diffused into the latex particles of network I and then formed network II by in situ polymerization. It indicates that the polymerization of network I obeys the classical kinetic rules of emulsion polymerization. But the polymerization of network II only appears a constant-rate stage and a decreasing-rate stage. The apparent activation energies (E-a) of network I and network II of PMMA/POA were calculated according to the Arrhenius equation. The E-a values of POA as network I (62 kJ/mol) is similar to that of POA as network II PMMA/POA (60 kJ/mol). However, the E-a value of PMMA as network II POA/PMMA (105 kJ/mol) is higher than that of PMMA as network I (61 kJ/mol). Results show that the E-a value of the network II polymerization is related to the properties of its seed latex. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 2116-2132, 2010