A new monomer 1,1-bis[(1-adamantyloxy)carbonyl]-2-vinylcyclopropane (3) was readily synthesized and polymerized by radical initiators. Monomer 3 afforded a 1,5-addition polymer selectively and in good conversion, even at high temperatures or low monomer concentrations. Poly(3) is soluble in common organic solvents, but insoluble in ether and methanol. Poly(3) (M n = 51 000 estimated by GPC based on polystyrene standard) exhibited a grass transition at 34 °C and 10% weight loss at 377 °C under nitrogen. Monomer 3 showed a positive volume change (+4.5 ± 1.1%) upon polymerization. This phenomenon can be rationalized by several reasons, such as the depression of recyclization during propagation by bulky ester groups, conversion of the crystalline monomer to the amorphous polymer, and the fact that 3 contains a pair of large spreadable ester groups that may increase the free volume of the polymer matrix. The kinetics of the homopolymerization of 3 with AIBN was investigated in benzene. The rate of polymerization (R p) can be expressed by R p = k[AIBN]0.52[3]1.2, and the overall activation energy E a has been calculated to be 20.8 kcal/mol.