Gadolinium methacrylate (Gd(MAA)3) was synthesized by using gadolinium oxide and methacrylic acid as the starting materials and its self-polymerization kinetic was studied based on non-isothermal and isothermal analysis. Moreover, the monomer reactivity ratios of methyl methacrylate (MMA) and Gd(MAA)3 were evaluated by using Kelen-Tüd?s method. The thermal neutron shielding properties of PMMA and poly(MMA-co-Gd(MAA)3) were calculated by MCNP program. The results show that the self-polymerization of Gd(MAA)3 can be initiated by thermal and free radical and its activation energy was 103.35 kJ/mol or

58.55kJ/mol corresponding in the solid state or aqueous solution. The polymerization rate, Rp, under low conversion at 65? is expressed as Rp=K[M]1.05[I]0.60. The reactivity ratios of r1 (MMA) and r2 (Gd(MAA)3) are 0.225 and 1.340, respectively. The ability of

thermal neutron shielding of poly(MMA-co-Gd(MAA)3) is increased by gadolinium contents and is far better than PMMA.