OH- and NH2-Terminated Hyperbranched Polysiloxanes: Controlled Synthesis, Characterization, Toughening, and Reinforcing Epoxy Resin

A new silicon-containing hyperbranched polysiloxane (HAHBPs) is successfully synthesized via a one-pot A(2)+B-3 strategy using diethylene glycol and (3-aminopropyl)triethoxysilane (KH550) under solvent-free and catalyst-free conditions. Then, for the first time, the HAHBPs are used to modify epoxy resin E51. TGA results display significantly lower thermal stability compared with that of the neat epoxy resin. Experimental results also show that the addition of HAHBPs simultaneously improves flexural strength and impact strength. In particular, a great increase (2.48 times its original toughness) in the toughness of epoxy resin E51 is achieved with 20wt% HAHBPs loading. More importantly, fracture morphology and DMA measurements show no obvious phase separation due to the strong interfacial bonds between the HAHBPs and epoxy matrix. These results indicate that the HAHBPs containing OH- and NH2- can be a potentially effective epoxy resin toughener.