Polyimide–polyformal block copolymers

In an effort to combine and tailor the properties of thermoplastic resins we have investigated the synthesis of polyimide–polyformal block copolymers prepared by the condensation reaction of α,ω-diamino functionalized polyformal oligomers with α,ω-dianhydride terminated polyimide oligomers. Amino functionalized polyformal oligomers were synthesized by displacement condensation reactions of various bisphenols with methylene dihalides in the presence of base and aminophenols. Oligomeric aromatic polyformals having weight average molecular weights (MW_w) of 7500 to 40,000 were obtained. Anhydride terminated polyimide oligomers with molecular weights (MW_w) ranging from 10,000 to 15,000 were obtained by the condensation of bisphenol-A–dianhydride and aromatic amines. Combining the polyimide oligomers with the polyformal oligomers in dipolar aprotic or nonpolar solvents afforded the desired block copolymers. The polyimide–polyformal block copolymers generally display two distinct glass transition temperatures by differential scanning calorimetry. The (AB)_n block copolymers were evaluated by TGA in both air and N₂ for thermal/oxidative stability.