Polyimide-based aerogel foams, via emulsion-templating

An oil-in-oil emulsion-templating method is used to fabricate polyimide aerogel foam materials. These materials contain micrometer size voids (macrovoids) in conjunction with inherently produced meso- and macropores in polyimide gels. Polyamic acid is first synthesized from diamines and dianhydrides and then chemically imidized to obtain a sol. An immiscible oil-type dispersed phase is introduced in the sol via emulsification and the sol is subsequently allowed to transition into a gel, thereby locking the dispersed phase droplets within the structure. The gel is subsequently dried under supercritical conditions to obtain aerogel foams. This paper evaluates the stability of the oil-in-oil emulsion used for templating with reference to the gel times of the continuous phase. Specifically, the effects of surfactant concentration on macrovoid size, mesopore size, and mechanical properties of the aerogel foams are investigated. In addition, water and oil absorption behavior of the aerogel foams are studied.