AbstractDihydroxy telechelics are precursors for the synthesis of multiblock copolymers. In order to synthesize high molecular weight polymers with good elastic properties it is necessary to gain detailed knowledge of the reaction behavior of these precursors. Therefore it was explored whether the polyaddition reaction of polyester-diols can be established in a robotic synthesizer platform to facilitate the elucidation of reaction characteristics. A series of 16 reactions was performed using a telechelic polyester and trimethylhexamethylene diisocyanate. The chain extension behavior of the building block was compared with respect to the Carothers equation. It was found, that the chain extension behavior follows the expected trend. The molecular weight of the polymers increased when the optimal ratio of reactive groups was approached.