Synthesis and properties of soluble fluorinated poly(ether imide)s with different pendant groups

Two types of new fluorinated diamine monomer, [1,4-(4-amino-2-trifluoromethyl-phenoxy)-2-(3′-trifluoromethylphenyl) benzene (III)] and [1,4-(4-amino-2-trifluoromethyl-phenoxy)-2-(3′-methylphenyl) benzene (IV)] were synthesized and polymerized with aromatic dianhydrides. A series of soluble poly(ether imide)s (PEIs) were prepared from the diamines and dianhydrides by two-step chemical imidization methods. Experimental results indicated that all the PEIs had glass transition temperature between 230 °C and 247 °C, the temperature at 5% weight loss between 527 °C and 598 °C under nitrogen. The membranes hand tensile strengths in the range of 74–101 MPa, tensile modulus in the range of 1.9–2.6 GPa, and elongation at break from 20 to 28%. The cast membranes also exhibited high optical transparency, with a UV–vis absorption edge of 354–406 nm. Moreover, these PEIs membranes possessed low dielectric constants of 2.63–3.20 (at 1 MHz) and low water uptakes (<0.75 wt%).