Novel Semi-Fluorinated Poly(ether imide)s Derived From 4-(p-Aminophenoxy)-3-trifluoromethyl-4 0 - aminobiphenyl Vijay Kute, Susanta Banerjee* Synthetic Chemistry Division, Defence Research & Development Establishment, Jhansi Road, Gwalior, 474002, India Fax: 0091-751- 2341148; E-mail: susanta_b20012001@yahoo.com Received: May 29, 2003; Revised: July 27, 2003; Accepted: September 3, 2003; DOI: 10.1002/macp.200350070 Keywords: dielectric constant; glass transition; mechanical properties; thermal stability; unsymmetrical diamine monomer Introduction Polyimides are of great interest because they exhibit a number of outstanding properties, such as excellent thermal and thermo-oxidative stability, solvent resistance, mecha- nical, and electrical properties. [1] These materials have been considered for use in numerous applications that require robust organic materials, including composites and precursors for high-performance aerospace materials as well as membranes for gas separation. Polyimides with a low dielectric constant, low refractive index, low water absorption, and a low coefficient of thermal expansion are being explored for interlayer dielectrics in electronic de- vices such as integrated circuits. [2] The main drawbacks of these classes of polymers are their insolubility and intractability, which causes difficul- ties in both synthesis and processing. Therefore, the pro- cessing of the polyimides is generally carried out via soluble poly(amic acid) precursors, which are cast onto a glass plate and then converted into thin polyimide films by a rigorous thermal treatment. However, this process has severe inherent limitations, like the emission of volatile byproducts during curing, and storage instability of the poly(amic acid) intermediate. [1] To utilize the thermal stability of poly(imide)s for further applications, and also to take advantage of other properties of these classes of polymers, such as high chain rigidity, packing density, and polar chain interactions for different applications, it is desirable to synthesize soluble and/or melt-processable variations. Solubilization of the poly- imides has been targeted by several means, such as intro- duction of flexible linkages, [3] bulky substituents [4] or bulky units in the polymer backbone, [5] or noncoplanar [6] or alicyclic [7] monomers. The main concept behind all these Full Paper: An unsymmetrical diamine monomer 4-(p- aminophenoxy)-3-trifluoromethyl-4 0 -aminobiphenyl has been synthesized successfully. This monomer leads to the synthesis of different novel poly(ether imide)s when reacted with dif- ferent dianhydrides like pyromellatic dianhydride (PMDA), benzophenone tetracarboxylic acid dianhydride (BTDA), 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane (6FDA), and oxy diphthalic anhydride (ODA). The poly(ether imide) prepared from this monomer on reaction with 6FDA is soluble in several organic solvents such as N-methylpyrolidi- none (NMP), dimethylformamide (DMF), N,N-dimethyl- acetamide (DMAc), tetrahydrofuran (THF), and CHCl 3 . The poly(ether imide)s prepared from BTDA and ODA are soluble in NMP, DMF, and DMAc but not in THF or CHCl 3 , whereas the polymer prepared from PMDA is soluble only in NMP. The water uptake value for these poly(ether imide) films is very low (0.2–0.5%), and exhibited low dielectric constants (2.81 at 1 MHz). The polymers exhibited high thermal stability up to 532 8C in air for 5% weight loss, and high glass transition temperatures up to 288 8C. The poly- mer exhibited high tensile strength up to 135 MPa, modulus 3.2 GPa, and elongation at break up to 25%, depending on the exact polymer structure. The structure of the poly(ether imide) synthesised from 4- (p-aminophenoxy)-3-trifluoromethyl-4 0 -aminobiphenyl and 2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane. This poly- mer was soluble in many organic solvents. Macromol. Chem. Phys. 2003, 204, 2105–2112 2105 Macromol. Chem. Phys. 2003, 204, No. 17 DOI: 10.1002/macp.200350070 ß 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim