Semi- and full-interpenetrating polymer networks (IPNs) were prepared using polyurethane (PUR) produced from a canola oil-based polyol with primary terminal functional groups and poly(methyl methacrylate) (PMMA). The properties of the material were studied and compared using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and tensile measurements. The morphology of the IPNs was investigated using atomic force microscopy (AFM). Semi-IPNs demonstrated different thermal mechanical properties, mechanical properties, phase behavior, and morphology from full IPNs. Both types of IPNs studied are two-phase systems with incomplete phase separation. However, the extent of phase Separation is significantly more advanced in the semi-IPNs compared with the full IPNs. All the semi-IPNs exhibited higher values of elongation at break for all proportions of acrylate to polyurethane compared with the corresponding full IPNs. These differences are mainly due to the fact that in the case of semi-IPNs, one of the constituting polymers remains linear, so that it exhibits a loosely packed network and relatively high mobility, whereas in the case of full IPNs, there is a higher degree of crosslinking, which restricts the mobility of the chains. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 139-148, 2009