Synthesis and characterization of fluorinated copolyetherimides with -CH2-C6F13 side chains based on the ULTEM structure

Step polymn. of bisphenol A diphthalic anhydride (BAPA) with various mixts. from m-phenylene diamine (m-PDA) and 2-(perfluorohexylmethyl)butan-1,4-diamine (TFD) led to hydrophobic copolyetherimides bearing RF = CH2C6F13 side chains that were characterized by NMR, element anal., DSC, TGA and surface energy anal. By increasing the TFD unit %, the glass transition temp. (Tg) decreases according to the Fox equation from 217° (m-PDA 100% and TFD 0% like in ULTEM 1000) to 113° (m-PDA 0% and TFD 100%). Similarly, the surface energy (γs) decreases from 45.3 mJ m-2 to 27.4 mJ m-2. The thermal decomposition temperature (Td for 5% weight loss under argon) is slightly affected by introducing TFD units compared with Td for ULTEM™ and it is close to 400 °C. The best compromise between thermal stability, hydrophobic and organophilic properties as well as the ability to form a soft non-porous film by the cast-evaporating method led us to select the copolyetherimide with m-PDA 25% and TFD 75% for which Tg = 121 °C, Td = 400 °C and γs = 30.8 mJ m−2.