Activated bentonite (Maghnite-H+) as green catalyst for ring-opening polymerization of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane

A new green technique to synthesize polysiloxane-type polymers is suggested based on use of chemically modified clay (Maghnite-H + ) as heterogeneous, cost-effective, environmentally friendly catalyst for polymerization of 1,3,5,7-tetravinyltetramethylcyclotetrasiloxane (V4D4) under gentle conditions and without solvent. Maghnite-H + is an ion-exchanged montmorillonite prepared by treatment with sulfuric acid, which leads to increased interplanar spacing due to intercalation of acid protons between sheets, a crystalline change clearly seen in the X-ray diffraction (XRD) spectrum. Polymers obtained under different conditions were characterized by infrared (IR) and 1 H and 13 C nuclear magnetic resonance (NMR) analyses and their thermal behavior studied by differential scanning calorimetry (DSC) analysis. The average molecular mass and dispersity were followed by gel permeation chromatography (GPC) by varying the operating conditions. A reaction mechanism is proposed to understand the role played by Maghnite-H + during the various stages of the reaction.