Mechanism and kinetics of melt transesterification with siloxane diol

Chemical reactivity will have new traits in system combining organic and silicon compounds. In this paper, the kinetics of melt transesterification of dimethyl terephthalate (DMT) with a siloxane diol of 1,3-bis(3-hydroxypropyl)-1,1,3,3-tetramethyldisiloxane (HP-TMDS) was fitted on the premise of the reaction mechanism obtained by quantum-chemistry calculation. This work reveals that the siloxane diol changes the reaction process and gives the classical transesterification its peculiarity, including more obvious advantage in kinetics for cyclic dimer and limited compatibility between reactant and catalyst. A solution is proposed to solve the problem resulting from the limited compatibility, which can be reference to any similar systems. The obvious advantage in kinetics for cyclic dimer brings a distinct feature in the product composition, which will provide more flexible and effective way to prepare silicon-containing polyesters.