Thermally stable soluble polymers prepared via the tris(pentafluorophenyl)borane-catalyzed polymerization of hydrosilyl-functionalized cage octasiloxane

In this study, we successfully prepared soluble polymers via the tris(pentafluorophenyl)borane (BCF)-catalyzed hydrosilylation of dimethylhydrosilyl-functionalized cage octasiloxane (DMHS-OS) and acetone, followed by dehydrocarbon condensation polymerization (Piers–Rubinstzajn reaction) between the unreacted hydrosilyl (Si–H) groups and converted isopropoxysilyl (Si–OiPr) groups of DMHS-OS. Notably, polymer Poly(DMHS-OS)-5, formed at a feed molar ratio of Si–H groups to acetone of 8:5, exhibited a relatively high weight-average molecular weight (Mw = 2.11 × 104). On the basis of the 1H NMR, 29Si NMR, and gel permeation chromatography results, Poly(DMHS-OS)-5 consists of approximately 17–18 linked cage octasiloxane repeating units. Despite the presence of alkoxysilyl groups, such as Si–OiPr, in the side chains, immersion in purified water for 1 h did not affect the solubility of the polymer, indicating its good water stability. Thermogravimetric analysis revealed that the 10% weight loss temperature of Poly(DMHS-OS)-5 was 535 °C and only 21% weight loss occurred at 1000 °C, indicating exceptionally low thermal degradation. These findings highlight the remarkably high thermal stability of the soluble polymer Poly(DMHS-OS)-5. Soluble polymers were prepared by polymerizing dimethylhydrosilyl-functionalized cage octasiloxane (DMHS-OS) using a tris(pentafluorophenyl)borane (BCF) catalyst through hydrosilylation with acetone, followed by dehydrocarbon condensation. Poly(DMHS-OS)-5, formed at a feed molar ratio of Si–H groups in DMHS-OS to acetone of 8:5, exhibited a weight-average molecular weight (Mw) of 2.11 × 104 and consisted of ca. 17–18 linked DMHS-OS units. It demonstrated high thermal stability, with a 10% weight loss temperature (Td10) of 535 °C and a weight loss of only 21% at 1000 °C.