Microphase separation occurred in all polymethyl methacrylate graft urethane copolymer(PMMA-g-UM2 )and poly normal but methacrylate (PnBMA-g-UM2 )copolymers: two glass transitions temperatures corresponding to the PMMA or PnBMA and UM2 fractions, respectively, were observed. On the other hand, Dynamic mechanical analysis ( DMA) and Differential scanning calorimetry (DSC) results showed that in most graft copolymer products the two respective component parts PMMA-g-UM2 or PnBMA-g- UM2 were compatible, because only one Tg was observed. Two glass transitions occurred for PMMA or PnBMA and UM2 when the amount of UM was increased to 55 wt % during copolymerization and microphase separation was evident in DSC, DMA and Transmission electron microscopy TEM measurements. Thermal stability and storage modulus (stiffness) of all the synthesized PMMA-g-urethane and PnBMA-g-urethane copolymers increased as the concentration of urethane macromonomer in the copolymerization feed increased, as confirmed in TGA and DMA results.