New insights into the nanostructure of high-C SiOC glasses obtained via polymer pyrolysis

High-C SiOC glasses have been synthesised starting from linear and cyclic SiH-containing polysiloxanes through sililisation. The amount of C has been increased by using divinylbenzene as a crosslinking agent. SiOC glasses have been obtained by pyrolysis in inert atmosphere at temperatures ranging from 1000 to 1400°C. The nanostructure of the SiOC glasses was investigated using a multiple technique approach on the SiOC glasses before and after HF etching. The acid attack dissolves the silica-based nanoclusters and thus provides indirect information on their size and quantity. HF etched SiOC glasses are highly porous with surface areas up to 460 m2/g and pore sizes in the range 3-4 nm. Finally, the study clearly shows that the structure of the precursor has a strong impact on the nanostucture of the final glass.