The dynamic fatigue properties of a new class of polyisobutylene (PIB)–based thermoplastic elastomers (TPE), consisting of polyalloocimene (PAllo) hard segments and PIB soft segments, have been investigated by the hysteresis method1,2. Both diblock and tetrablock copolymers were synthesized using the industrial butyl rubber polymerization system in emulsion3,4, as opposed to the expensive TiCl4–based living solution polymerization systems. This was the first report of a diblock copolymer structure showing TPE properties.4 The dynamic fatigue properties of the new TPE materials (both diblock and tetrablock) were compared to polystyrene-b-PIB-b-polystyrene (SIBS) and silicone rubber. Furthermore, the new TPEs showed excellent filler interaction, in contrast to SIBS: 60 phr (37.5 wt%) carbon black reduced the absolute dynamic creep from 98.2 % and 18.8 % to 24.2 % and 8.6 % of the neat diblock and tetrablock, respectively. References 1. El Fray, M.; Altstӓdt, V., Polymer, 2003, 44, 4635-4642. 2. El Fray, M.; Altstӓdt, V., Polymer, 2003, 44, 4643-4650. 3. Puskas, J.E.; Kaszas, G.; Gergely, A.L. US Provisional Patent Application # 61/587,736. January, 2011. 4. Puskas, J.E.; Gergely, A.L.; Kaszas,G., J. Polym. Sci. Part A: Polym. Chem., 2013, 51(1), 29-33.