Azo initiators for the preparation of hydroxyl‐terminated polybutadienes

Azo compounds such as di(4‐hydroxybutyl)‐2,2′‐azobisisobutyrate, di(3‐hydroxybutyl)‐2,2′‐azobisisobutyrate, di(2‐hydroxypropyl)‐2,2′‐azobisisobutyrate, and di(2‐hydroxyethyl)‐2,2′‐azobisisobutyrate were prepared and used as initiators for the preparation of hydroxyl‐terminated polybutadienes (HTPBs) of molecular weight (M̄n) ranging from 2000 to 7500 and functionality between 1.90 and 3.0. The polymers were prepared by free‐radical solution polymerization in dioxane and toluene. The polymers obtained were characterized for their molecular weight, hydroxyl number, functionality, and instrinsic viscosity.