Head to head polymers. XXV: Properties of head to head polyisobutylene

AbstractHead‐to‐head polyisobutylene, prepared by the Grignard coupling reaction of 2,2,3,3‐tetramethyl‐1,4‐dibromobutane had molecular weight of 3,000 to 10,000 and was characterized by wide angle x‐ray diffraction, optical microscopy and thermal behavior. Head‐to‐head polyisobutylene is crystalline, with a crystalline melting point of 187°C and a glass transition temperature of 87°C (measured by DSC at a scan rate of 20°/min.); these values compare to a glass transition temperature of head‐to‐tail polyisobutylene of similar molecular weight of −61°C and a crystalline melting point of 5°C, which can only be observed when the sample was stretched. The maximum rate of degradation of head‐to‐head polyisobutylene (20°/min. programmed temperature increase) is at 315°C, 70°C lower than that of head‐to‐tail polyisobutylene.