Notes High Thermal Stability and Rigid Rod of Novel Organosoluble Polyimides and Polyamides Based on Bulky and Noncoplanar Naphthalene-Biphenyldiamine Der-Jang Liaw,* ,† Feng-Chyuan Chang, † Man-kit Leung, ‡ Meng-Yen Chou, ‡ and Klaus Muellen § Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan, ROC; Department of Chemistry, National Taiwan University, Taipei, Taiwan, ROC; and Max-Planck-Institute for Polymer Research, Ackermannweg 10, Mainz 55128, Germany Received July 15, 2004 Revised Manuscript Received January 18, 2005 Introduction Rigid-rod aromatic polyimides and polyamides con- stantly attract wider interest because of their unique mechanical, thermal, and morphological properties. 1-7 Synthesis and processing of these materials are gener- ally more difficult due to their limited solubility and infusibility. One of the successful approaches to increase solubility and processability of polymers is by the introduction of bulky lateral substituents, 8-11 flexible alkyl side chains, 12,13 unsymmetric, 14 alicyclic, 15,16 and kinked structure. 17-20 To develop easily processable high-performance materials, modifications that increase the solubility while maintaining the rigid-rod character and the thermal stability are of particular interest. Another approach employed to increase the solubility of rigid-rod polyimides and polyamides is by incorpora- tion of the nonlinear moieties such as a bulky nonco- planar group in the polymer backbone. In a previous study, 21-28 the solubility, thermal and thermooxidative stability, optical properties, transition, and relaxation behaviors of organosoluble aromatic polyimide could be improved by addition of 2,2′-disubstituted groups like methyl, cyano, trifluoromethyl groups, methyl-substi- tuted phenyl groups, halogens, methacrylate, sulfonic acid, trifluoromethylphenyl groups, and biphenyl groups substituted at different positions to main-chain 4,4′- diaminobiphenyls. The 2,2′-disubstituted biphenylylene moiety could be considered as a rodlike structure and adopts a noncoplanar conformation in the presence of methyl substitution at the 2,2′-position. The substitution at the 2- and 2′-positions of the biphenyl moiety forces the rings out of the plane into adopting a noncoplanar conformation. 23,27,28 Naphthalene structure is bulky and rigid which also has high heat resistance. 29,30 Incorpora- tion of the naphthalene group at the 2,2′-position of biphenylylene may disrupt the crystal packing, reducing intermolecular interactions and enhancing solubility of the polyimide and polyamide. In the present paper, we will report the synthesis of a new naphthalene-substituted monomer, 2,2′-dinaph- thylbiphenyl-4,4′-diamine, and its use in the preparation of soluble polyimides and polyamides by the reaction of the diamine with commercial dianhydrides and dicar- boxylic acids. The solubility, tensile properties, thermal properties, electrochemical stability, and dielectric con- stants of the obtained polyimides and polyamides are also investigated. Experimental Section Materials. Reagent-grade aromatic tetracarboxylic dian- hydrides such as 4,4′-hexafluoroisopropylidenediphathalic an- hydride (6FDA) (I-1), 4,4′-sulfonyldiphthalic anhydride (DSDA) (I-2), and 3,3′,4,4′-benzophenone-tetracarboxylic dianhydride (BTDA) (I-3) and aromatic dicarboxylic acids such as iso- phthalic acid (II-1), 5-tert-butylisophthalic acid (II-2), 4,4′- sulfonyldibenzoic acid (II-3), and 4,4′-hexafluoroisopropyli- denedibenzoic acid (II-4) were used after purification by crystallization. Reagent-grade calcium chloride was dried under vacuum at 180 °C before use. N-Methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylform- amide (DMF), pyridine, dimethyl sulfoxide (DMSO), triphenyl phosphite (TPP), γ-butyrolactone, and cyclohexanone were purified by distillation under reduced pressure over calcium hydride and stored over 4 Å molecular sieves. Measurements. IR spectra of synthesized monomers and polymers (KBr disks) were recorded in the range 4000-500 cm -1 on a Jasco IR-700 spectrometer. Melting point was recorded on a MEL-TEMP II. The inherent viscosities of all polymers were measured using a Ubbelohde viscometer. Nuclear magnetic resonance (NMR) spectra were recorded on a Varian VXR400S ( 1 H at 399.96 MHz and 13 C at 100.58 MHz). Mass spectra (MS) were recorded by a Joel JMS-HX 110. Elemental analysis (EA) was recorded by a Heraeus CHN-O Rapid. Thermogravimetric data were obtained on a TA 5100 thermal analysis system under nitrogen flowing conditions nitrogen (60 cm 3 min -1 ) at a heating rate of 10 °C min -1 . Differential scanning calorimetric analysis was performed on a differential scanning calorimeter (TA Instruments TA-2010) at a heating rate of 10 °C min -1 . Tensile properties were determined from stress-strain curves obtained with a Orientec Tensilon with a load cell of 10 kg. A gauge of 2 cm and a strain rate of 2 cm min -1 were used for this study. Measurements were performed at room temperature with film specimens of dimensions 0.4 cm wide, 5 cm long, and 0.1 mm thick. Dielectric constants of polyimide thin film were measured by the parallel-plate capacitor method using a dielectric analyzer (TA Instruments DEA 2970) at a frequency of 1 kHz. Gold electrodes were vacuum-deposited on both surfaces of dried films, and measurements were made at 25 °C under a N 2 atmosphere. Electrochemical stability was measured by a cyclic voltammetry instrument BAS CV-27 voltammograph. The method is (0-1.5 V, 100 mV/s) in DMF using Bu4NClO4 (0.1 M) as the supporting electrolyte. The signals were obtained on a platinum working electrode, with a Pt wire as the counter electrode and a Ag/AgCl (saturated) electrode as the reference electrode. † National Taiwan University of Science and Technology. ‡ National Taiwan University. § Max-Planck-Institute for Polymer Research. * Corresponding author: Fax 886-2-23781441 or 886-2-27376644; e-mail liaw@ch.ntust.edu.tw or liaw8484@yahoo.com.tw. 4024 Macromolecules 2005, 38, 4024-4029 10.1021/ma048559x CCC: $30.25 © 2005 American Chemical Society Published on Web 03/30/2005 Downloaded by NATIONAL TAIWAN UNIV on July 29, 2009 Published on March 30, 2005 on http://pubs.acs.org | doi: 10.1021/ma048559x