The synthesis and characterization of a series of novel (AB).sub.n multiblock copolymers, typically thermoplastic elastomers, containing polyisobutylene as the soft phase and polyamides as the hard phase are described. First, carboxyl ditelechelic polyisobutylene prepolymers and isocyanate ditelechelic polyisobutylene prepolymers were synthesized, both of which were subsequently reacted under solution polycondensation conditions with dicarboxylic acids and diisocyanates. The melting points of the polyamide hard phases were in the 223.degree.-284.degree. C. range. The decomposition temperatures (296.degree.-337.degree. C.) in air and nitrogen of these thermoplastic elastomers were quite similar; in contrast, these properties of polytetrahydrofuran-based thermoplastic elastomers are noticeably lower in air. Melt processing of these novel polyisobutylene-based thermoplastic elastomers is possible.