Poly-perfluoroalkyl substituted polyethyleneimine compositions are provided that act as foam stabilizers and film formers when used in fire-fighting foam concentrates. The polyethylene compositions are soluble in water, but have only low solubility in polar solvents. When aqueous film forming foam generated from these concentrates is applied to burning polar solvent the polyethyleneimine compositions precipitate at the polar solvent/foam interface and inhibit the collapse and destruction of the foam.
