Highly Organosoluble and Flexible Polyimides with Color Lightness and Transparency Based on 2,2-Bis[4-(2- trifluoromethyl-4-aminophenoxy)-3,5- dimethylphenyl]propane DER-JANG LIAW, FENG-CHYUAN CHANG Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan 106 Received 13 April 2004; accepted 1 June 2004 DOI: 10.1002/pola.20326 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: A new diamine containing isopropylidene, methyl substituted arylene ether, and trifluoromethyl groups, 2,2-bis[4-(2-trifluoromethyl-4-aminophenoxy)-3,5- dimethylphenyl]propane (BTADP), was synthesized and used in preparation of a series of polyimides by direct polycondensation with various aromatic tetracarboxylic dian- hydrides in N, N-dimethylacetamide (DMAc). All polymers derived from diamine (BTADP) with trifluoromethyl substituents were highly organosoluble in the solvents, like N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide, N,N-dimethylform- amide (DMF), pyridine, chloroform, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dichloromethane, cyclohexanone, and -butyrolactone at room temperature or upon heating at 70 °C. Inherent viscosities of the polyimides were found to range between 0.58 and 0.97 dLg -1 . These polyimides had glass transition temperatures between 256 and 307 °C, and their 10% mass loss temperatures ranged from 440 to 462 °C and 421 to 443 °C under nitrogen and air, respectively. These polyimides had low dielectric constants in the range of 2.84 –3.09. All the polyimides could be cast into films from DMAc solutions and were thermally converted into color lightness, optically transparent, flexible, and tough polyimides. The polyimide films had a tensile strength in the range of 83–97 MPa and a tensile modulus in the range of 2.0 –2.2 GPa. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5766 –5774, 2004 Keywords: polycondensation; polyimides; transparency INTRODUCTION Organic polymers containing imide groups in the main chain have excellent thermal stability and mechanical properties, good chemical resistance, high dimensional stability, and good electric prop- erties. 1–4 Conventional polyimides like Kapton produced by Du Pont have been applied to micro- electronic devices and aerospace fields. However, these polyimides are generally insoluble in or- ganic solvent, exhibit low optical transparency, and have intense yellow color. Soluble polyimides are needed as coating materials on specific space components. Polyimides with high optical trans- parency are also required as liquid crystal display devices. 5,6 Solubilizations of the polyimides have been tar- geted by several means, such as the incorporation of bulky pendant group, 7–9 flexible linkages, 10 –12 and noncoplanar biphenylene moieties 13,14 into the polymer backbones. The main concepts indi- cate all of these approaches in the reduction of several types of polymer chain-chain interactions, reduction of chain packing, and charge-transfer Correspondence to: D.-J. Liaw (liaw@ch.ntust.edu.tw). Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 42, 5766 –5774 (2004) © 2004 Wiley Periodicals, Inc. 5766