Cohesion energy density of 1

2-polybutadienes with various content of 1

2-unit was obtained from solubility parameter which was measured in mixed solvents of cyclohe-xane and toluene.It was found that with increasing in the content of 1

2-unit of the polymer

its glass transition temperature increases but the cohesion energy density decreases

due to the stiffening of the molecular chains of 1

2-polybutadienes.