A new hyperbranched poly(arylene-ether-ketone-imide): Synthesis, chain-end functionalization, and blending with a bis(maleimide)

While aromatic polyimides have found widespread use as high-performance polymers, the present work addressed the need for organosoluble pre-imidized materials through the use of a hyperbranching scheme. The AB₂ monomer, N-[3,5-bis(4-hydroxybenzoyl)benzene]-4-fluorophthalimide, was prepared from 4-fiuoroisophthalic anhydride and 3,5-bis(4-hydroxybenzoyl)aniline. The latter was synthesized in three steps starting from commercially available 5-nitroisophthalic acid. The AB₂ monomer was then polymerized via aromatic fluoride-displacement reaction to afford the corresponding hydroxylterminated hyperbranched polymer, HT-PAEKI, which was then functionalized with allyl and propargyl bromides as well as epichlorohydrin to afford allyl-terminated AT-PAEKI, propargyl-terminated PT-PAEKI, and epoxy (glycidyl)-terminated ET-PAEKI, in that order. All hyperbranched poly(ether-ketoneimide)s were soluble in common organic solvents. Intrinsic viscosities of HT-, AT-, PT-, and ET-PAEKI in NMP were 0.13, 0.08, 0.08, and 0.08 dL/g, in that order. AT-PAEKI displayed an exotherm due to Claisen rearrangement at 269 °C and allyl-based thermal-cure reaction at 343 °C. PT-PAEKI displayed only a single, strong exotherm at 278 °C. Because of hydrogen bonding, HT-PAEKI displayed T_g of 224 °C while its derivatives exhibited lower T_g values ranging from 122 to 174 °C. Finally, AT-PAEKI was blended with a bisphenol A-based bis(maleimide) (BPA-BMI) in various weight ratios. The results from differential scanning calorimetric study indicated that the presence of AT-PAEKI (up to 32 wt %) significantly affect the glass transition temperatures and cure behavior of BPA-BMI. Dynamic mechanical analysis comparing cured BPA-BMI with the 5 wt % AT-PAEKI blend corroborates this increase in glass transition temperature.