Restricted assembly of ultralow loading of graphene oxide for lightweight, mechanically flexible and flame retardant polydimethylsiloxane foam composites

Lightweight, mechanically flexible and flame retardant polydimethylsiloxane (PDMS) foam materials modified with low content of nano-fillers are highly needed for versatile applications. Instead of the direct mechanical mixing technique that induced the embedment of nanofillers inside the matrix, herein, a facile, rapid and green restricted assembly strategy was established to prepare PDMS foam composites coated with an extremely low content of restricted graphene oxide (GO) sheets. A GO/water mixture in silicone oil emulsion was prepared to produce the restricted assembly of GO layers precisely and solely on the foam surface with no GO sheets inside the skeleton. Based on such restricted assembly induced by the amphiphilic surfactant molecules, the presence of only ∼0.04 wt% GO greatly improved the flame resistance (e.g., 40.6% reduction in heat release rate and 27.1% of limit oxygen index) of PDMS foams without affecting the low density (∼0.23 g/cm 3 ) and mechanical flexibility (unchanged stress at strain 70% after 100 cycles under 200 °C). Observations and analysis of the burnt zones demonstrated that the restricted ultra-low content GO sheets formed a compact protective layer facilitated by the pyrolysis of the PDMS molecules, therefore protecting the inside of the PDMS material from the heat and oxygen attacks. These results confirmed that the restricted self-assembly of 2D nano-fillers approach is effective for the fabrication of flame-retardant PDMS foams and retention of other important properties.