Low-Cost, Ambient-Dried, Superhydrophobic, High Strength, Thermally Insulating, and Thermally Resilient Polybenzoxazine Aerogels

A family of ambient-dried polybenzoxazine aerogels is prepared with a facile and scalable process as a high-performance polymeric aerogel with strong and robust thermomechanical properties at elevated temperatures. Those materials are inherently flame-retardant and superhydrophobic over the entire bulk density range (0.24-0.46 g cm(-3)). In addition, they are mechanically strong with strengths (e.g., 1 MPa at 0.24 g cm(-3) at room temperature) higher than those of other high-performance aerogels of similar density, including polyimide and polyamide (Kevlar-like) aerogels as well as polymer-cross -linked X-silica and X-vanadia aerogels, at a significantly lower cost. Furthermore, unlike most other glassy polymeric materials, the maximum strength of the synthesized aerogels occurs at service temperatures slightly higher than room temperature (about 50 degrees C), which eliminates the possibility of any drop in strength with respect to the room temperature strength up to 150 degrees C at all densities. At higher temperatures (up to 250 degrees C), the overall performance of those aerogels is also stable and robust without any significant drop in Young's modulus or strength levels, which makes them suitable for various industrial applications including high-performance structural and thermal protection applications as an alternative to the significantly more expensive polyimides.