Pd-diimine complexes catalyze polymerization of 1,6,11-dodecatrienes having cyclic ester groups at the 4 and 9 positions to produce the polymers containing two trans-five-membered rings in the structural units. The doublecyclopolymerization of triene with cyclic acetal group yields the polymer with narrow molecular weight distribution (M-w/M-n = 1.20-1.66). The two five-membered rings in a monomer unit of these polymers are linked directly with racemo stereochemistry. Relative stereochemistry of the monomer units separated by ethylene spacer changes depending on the monomer and catalyst, and 91% syndioselectivity is obtained in the polymerization of the triene with cyclic acetal groups. Hydrolysis of the polymer containing cyclic acetal groups yields the polymer containing CH2OH groups.