A series of polymers 3 bearing (eta(5)-cyclopentadienyl)cobaltacyclopentadiene moieties in the main chain and flexible aliphatic alkoxy groups in both the main and side chains has been synthesized. Polymers 4 having (eta(5)-cyclopentadienyl)(eta(4)-cyclobutadiene) moieties were obtained by the thermolysis of toluene solutions of the corresponding polymers 3. The resulting polymers of both series were soluble in common organic solvents. According to the thermal analysis data, polymers 3 underwent rearrangement to produce 4 upon heating (155-175 degrees C), while polymers 4 were stable before 410-425 degrees C. Glass transitions of polymers 4 were observed in the range -10 to +120 degrees C, depending regularly on the size of the aliphatic segments.