Novel acetylene-terminated polyimide oligomers with excellent processability and high toughness of films

A series of acetylene-terminated imide oligomers based on 2,3,3,4-Diphenyl ether tetracarboxylic acid dianhydride (a-ODPA), 3,4-Oxydianiline (3,4-ODA), and 3-Ethynylaniline (3-EA) with different molecular weights were synthesized by using acetic anhydride and triethylamine as dehydrating agent. Their main structure was confirmed by Fourier transform infrared spectroscopy (FT-IR). Thermal curing processing was characterized by FT-IR and differential scanning calorimetry (DSC). All the uncured imide oligomers showed excellent solubility (more than 30 wt %) in organic solvent such as N,N-dimethylacetamide (DMAc) and N-methyl-2-pyrrolidone (NMP). These imide oligomers also possessed a very low viscosity, thus provided better processing window. These oligomers were formulated into thermosetting films by thermal crosslinking of the ethynyl groups. The properties of cured films were evaluated by dynamic mechanical thermal analysis (DMA), thermogravimetric analysis (TGA), and tensile measurement. The glass transition temperature (T-g) and elongation at break of the cured films were found to be almost >260 degrees C and >9.2%, respectively. The cured films in air resulted in higher thermal stability than those under N-2 atmosphere. Experimental results suggested that the introduction of asymmetric and flexible ether-hinge with 3-EA in polyimide oligomers can improve the processability of the imide oligomers and the toughness for a cured sample without sacrificing their thermal-oxidative stability. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42537.