A series of polyurethane (PUR)/poly(ethyl methacrylate) (PEMA) simultaneous interpenetrating polymer networks (IPNs) with different PURJPEMA composition ratios was prepared and characterised. For each IPN, the glass transition behaviour was determined by dynamic mechanical thermal analysis (DMTA) and modulated temperature differential scanning calorimetry (M-TDSC), whereas the morphology was examined by transmission (TEM) and scanning electron microscopy (SEM). Finally, the mechanical and thermal properties were investigated using tensile testing and thermogravimetric analysis (TGA). [Continues.]