Graphene oxide-based silsesquioxane-crosslinked networks - synthesis and rheological behavior

Click reaction between octa(3-azidopropyl) polyhedral oligomeric silsesquioxane (POSS-(N-3)(8)) and heavily alkyne-decorated graphene oxide (GO) has led to crosslinking POSS with GO. Introducing POSS to GO and reduction of GO sheets by sodium ascorbate during click reaction has led to a hydrophobic and well organically dispersible material. Hydrophobic reduced graphene oxide crosslinked with polyhedral oligomeric silsesquioxanes (rGO-POSS) network showed high solubility in various organic solvents. GO, rGO, and rGO-POSS were used as fillers for fabricating polydimethylsiloxane nanocomposites for rheological investigations. While the larger GO-sheets led to a surprisingly low rheological percolation threshold, the significantly smaller rGO-POSS filled systems showed almost the same percolation threshold as GO-filled systems when only the graphenic part of the nanocomposites was considered. rGO-filled composites, which have the same low hydrophobicity and relatively small size as the rGO-POSS fillers, show a significantly higher percolation threshold, which is attributed to partial restacking of these fillers.