Abstract: A method of producing an impact modified polymer comprises dissolving a high-temperature polyetherimide and a high-temperature fluorelastomer in a common solvent to form a single phase solution which is heated to a temperature that would normally vaporize the solvent. The solution is maintained at an elevated pressure to avoid vaporization of the solvent. After being heated at the elevated temperature, the solution is subjected to flash evaporation by introducing the solution into a zone of reduced pressure. This forms a blend of the polyetherimide into which the fluorelastomer is micro-dispersed. A composition of matter formed by the method advantageously includes a solid component having 90% by weight ULTEM 1000 polyetherimide and 10% by weight VITON A fluorelastomer. Dimethyl formamide is advantageously used as the common solvent.