Chemical Modification of Fluorinated Polyimides:  New Thermally Curing Hybrid Polymers with POSS

A series of four new end-capped and hydroxymethyl-functionalized polyimides were prepared. Through a two-step chemical modification process (3-aminopropyl)(hepta-i-butyl) polyhedral oligomeric silsesquioxane (POSS) was covalently attached to the polymer backbone. POSS loading levels as high as 36 wt % could be obtained while maintaining excellent processability and optical clarity of thin films. Concurrent attachment of either a cyanate ester or hydroxyethyl methacrylate (HEMA) group afforded processable POSS-polyimides that underwent thermal curing to yield solvent-resistant films, both having final T g's of 251 °C. Kinetic analysis of the cure reactions yielded energy of activations of 93 kJ/mol (cyanate ester) and 103 kJ/mol (HEMA). Exposure of a POSS-polyimide containing ∼31 wt % POSS to atomic oxygen displayed no measurable level of erosion relative to a Kapton H standard.