Kinetics,mechanisms, and synthesis studies of difunctional aminopropyl terminated polydimethylsiloxane oligomers

The anionic ring opening equilibration polymerization of octamethylcyclotetrasiloxane (D₄) initiated with siloxanolates in the presence of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (DSX) was investigated. The disiloxane serves as an effective chain transfer agent and source of aminopropyl functionality. Techniques for following the polymerization utilizing gas chromatography and high pressure liquid chromatography (HPLC) were developed and verified to be comparable with alternate methods published in the literature. In these polymerizations, it was concluded that the quaternary siloxanolate led to much more rapid polymerizations than the corresponding potassium based initiators. In all cases, the cyclic tetramer disappeared more rapidly than the disiloxane. However, this does not limit the utilization of the DSX for the synthesis of controlled molecular weight, difunctional species. Polar impurities, such as water in the disiloxane, were shown to influence the reactivity in these systems, especially at relatively low initiator concentrations. The work is continuing and many issues are being addressed, currently in a more quantitative fashion using the analytical procedures developed in the current study.