Cyclo-linear synthesis of amino silicone oil and study on the catalytic polymerization mechanism of phosphazene base

Abstract

Polysiloxanes with amino functional groups exhibit remarkable backbone flexibility, lubricity, and softness, positioning them a promising class of polymer materials. The phosphazene base (Bu-t-P₄) serves as an effective catalyst for the ring-opening copolymerization (ROCP) of octamethylcyclotetrasiloxane (D₄) and N-β-(aminoethyl)-γ-aminopropylmethyldiethoxysilane (KH-602). Under catalysis by 100 ppm of Bu-t-P₄ at 110 °C for 1 h, high yield of 93.59 % was achieved, resulting in amino silicone oil with a number-average molecular weight of 4.3 × 10³ g/mol, and a narrow molecular weight distribution (2.00). Fourier-transform infrared spectroscopy and nuclear magnetic resonance (NMR) confirmed that the product's structure corresponds to expected chemical shifts. In situ Raman spectroscopy monitoring and NMR analysis was employed to propose and validate the polymerization mechanism within the Bu-t-P₄-catalyzed system involving both cyclic and linear monomers. This study demonstrates an effective strategy, affirming that Bu-t-P₄ can be used as an efficient organic catalyst for the modified polysiloxanes.