High modulus aliphatic polyimide from 1, 3-diaminopropane and ethylenediaminetetraacetic dianhydride: Water soluble to self-patterning

In this study, a fully aliphatic polyimide (FAPI) with ultra high modulus and hardness has been synthesized via 1, 3-diaminopropane and ethylenediaminetetraacetic dianhydride. The thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) studies revealed the thermal imidization process occurred at a low temperature, around 140-150 °C. The resulting aliphatic polyimide could not only quickly dissolve unconventional organic solvents including methylene chloride, N, N-dimethylformamide and N-methylpyrrolidone, but also in water at room temperature, which has not been reported before. Nanoindentation technique applied to evaluate mechanical properties of the synthesized FAPI indicated that the modulus (Er) and hardness (H) of FAPI was higher than 8 GPa and 0.3 GPa, respectively, which are approximately 200% of commercial polyimide products. According to Fourier transform infrared spectroscopy (FTIR) analysis of FAPI and structure analysis of the two monomers, the existence of nucleophilic trimethyleneamino group and its interaction with electrophilic carbonyl group were considered primarily accountable for both water solubility and high mechanical performances of FAPI. Higher imidization temperature (250 °C) resulted in the self-patterning of FAPI film, which was probably related to the hydrogen bonding induced assembling of poly(amic acid) as well as the cross-linking of FAPI at high temperature.