Effects of Diamines on the Optical Properties of Poly(ether imide)s Derived from 2,2-Bis[4-(3,4-dicarboxyphenoxy)phenyl]propane Dianhydride (BPADA)

Abstract

The objective of this study was to investigate the effects of diamines with ether group or/and trifluoromethyl (-CF3) group on the optical properties of polyimides. A series of poly(ether imide)s (PEIs) (III) were prepared from 2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl]propane dianhydride (BPADA) with various aromatic diamines (Ia-h) including non-fluorinated diamines (Ia-d) and the corresponding trifluoromethyl-substituted diamines (Ie-h). The fluorinated PEIs IIIe-h based on fluorinated diamines were nearly colorless with cutoff absorption wavelength (λ0) below 370 nm and with solubility higher than that of the corresponding CF3-free analogues (IIIa-d). Meanwhile, they had lower dielectric constants in the range of 2.91–3.21 at 1 MHz coupled with water absorptions below 0.70% and contact angles against water beyond 108°. The III series had tensile strength of 84.3–94.4 MPa, modulus of elasticity of 3.6–8.9 GPa and elongation at break of 9.4–25.3%, together with temperatures of 5% weight loss (T5%) beyond 510 °C. Compared to the IV series based on 4,4-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), the corresponding III series exhibited better thermal and mechanical properties coupled with good optical properties, especially the fluorinated PEIs IIIe-h.