Efficient organic-to-inorganic conversion of polysiloxane by novel platinum-thiol catalytic system

Novel platinum-thiol catalytic system was constructed by the combination of platinum (Pt) catalysts (Karstedt's catalyst (KC) and chloroplatinic acid hexahydrate (CPA)) and thiol-containing compounds ((3-mercaptopropyl)trimethoxysilane (SM), (3-mercaptopropyl)triethoxysilane (SE), 1,6-hexanedithiol (HDT) and 1-octadecanethiol (OT)). It was found that Pt-thiol catalytic system could remarkably enhance the organic-to-inorganic conversion of polydimethylsiloxane (PDMS) and methylvinylpolysiloxane (Vi-PDMS) at elevated temperature. Under optimal condition, the ceramic yield of KC/SE/Vi-PDMS with 50 ppm Pt (KC) and 0.5 phr SE at 1000 degrees C was dramatically improved from 0.6 wt% to 54.4 wt% in comparison with Vi-PDMS. FTIR, Raman spectroscopy, XPS and XRD revealed that amorphous free carbon-containing SiOC ceramics were formed after thermal treatment of KC/SE/PDMS and KC/SE/Vi-PDMS at 1000 degrees C for 60min. And during organic-to-inorganic conversion of Vi-PDMS under high temperature, Pt-thiol catalytic system can efficiently retain C in the inorganic network of SiOC ceramics with existence of vinyl. TG, TG-FTIR and viscosity test results suggested that Pt-thiol system might enhance radicals coupling of Vi-PDMS chains and suppress unzipping decomposition or random scission, which resulted in the high capacity of organic-to-inorganic conversion of KC/SE/Vi-PDMS at elevated temperature. (C) 2020 Elsevier Ltd. All rights reserved.