Abstract
A series of fluoropoly(ether‐imide) (6F‐PEI), and [6F‐PEI/montmorillonite (MMT) clay) nanocomposites films were made by thermal curing of respective formulations containing fluoropoly(ether‐amic acid) (6F‐PEAA), synthesized from 2,2′‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 4,4′‐bis(4‐aminophenoxy)diphenyl sulfone (p‐SED), and increasing concentration of p‐SED treated montmorillonite clay (modified MMT clay) at temperature from RT to 350 °C. These films showed excellent solvent resistance as well as very good thermal stability, and increased glass transition (T~g~) values with increasing % clay. In addition, these trifluoromethyl groups‐containing nanocomposites films showed sharp lowering of coefficient of thermal expansion (CTE) by 22%. Furthermore, they exhibited increased long‐term thermo‐oxidative stability (TOS), with % weight retention in the range of 86 to 92% in isothermal heating at 300 °C for 300 h in air, reduced water absorption at 100 RH at 50 °C in the range of 0.5 to 1.15%. These data are still much lower than those of neat ULTEM® 1000 and Kapton® H film. The modulus of elasticity is on an average 38% higher for the nanocomposite films relative to neat fluoropoly(ether‐imide) (6FDA + p‐SED), and above non‐fluorinated polyimide films. The surface energy measurement by One‐Liquid and Two‐Liquid method showed a comparable trend of decreasing contact angle. For the nanocomposite films having 15% hydrophobic clay, the contact angle decreased by 21 and 20% for DI‐water and formamide, respectively. The surface energy increase was in the range of 8.21–8.54 mJ/m^2^.
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