Multiblock terpolymers -(PBT-b-PTMO-b-PA12.10)n- comprising the polymer systems in which one of the three blocks (PBT) is not soluble in the hard phase of PA12.10 blocks
but is slightly soluble in the soft phase of PTMO blocks have been obtained. The DSC and DMTA method was applied to investigate
the thermal properties of these polymers and it was found that the PBT block acts as an element that produce stiffness of
-(PBT-b-PTMO-b-PA12.10)n- structure. The terpolymers were compared with the previously described  -(PBT-b-PTMO-b-PA12)n- elastomers, in which the rigid PBT block (DP > 7) dissolves in the hard phase of PA12 blocks and partly dissolves in the
soft phase. It was found that even a small change in the chemical structure of the amide block influences significantly on
the structure, phase separation and the properties of terpolymers.