Butyl elastomers with different degree of branching and molecular weight were prepared in laboratory batch polymerization experiments. Samples prepared ranged from high gel content to linear. Branching was achieved by the addition of divinyl benzene. Molecular weight was controlled by the addition of a strong chain transfer agent, 2,4,4-trimethyl-penetene-1 (TMP-1). In butyl polymerization, the transfer coefficient of TMP-1 was measured to be very similar to the value obtained in isobutylene homopolymerization. TMP-1 had no impact on conversion giving a zero poison coefficient. Long term relaxation properties of the linear samples could be fully described by the frequency of the cross over point located between the terminal and plateau region. The relaxation time calculated from the cross over frequency showed a 3.3 power dependence on molecular weight and it gave a linear relationship with Mooney relaxation results.