Rheology of star-branched polyisobutylene

The rheology of high molecular weight, six-arm-star polyisobutylenes (PIB) was measured and compared to the behavior of linear PIB. The polymers had e quivalent plateau moduli and conformed well in the terminal zone to the tim e-temperature superposition principle. Moreover, the temperature coefficien ts of the terminal relaxation times were identical for the star and linear polymers. Since the trans and gauche conformations in PIB have virtually th e same energy, this absence of enhanced temperature sensitivity in star PIB , as well at the thermorheological simplicity, is consistent with an interp retation of the rheology of branched polymers based on an arm retraction me chanism.