Biphenyl-type polyimide

Figure 7.2 Biphenyl-type polyimides and polyimides with a connecting group (-X-) between the phthalimides.

Starting materials and solvents were purchased from Aldrich Chemical Co. acetonitrile (ACN), N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP) were obtained anhydrous in Sure/Seal bottles and used as received. The polyamic acid of PMDA-ODA (2545 Pyralin) was supplied by DuPont. The soluble polyimide XU-218, derived from 3,3, 4,4 -benzophenone tetracarboxylic dianhydride (BTDA) and diamino-1,1,3-trimethyl-3-phenylindan isomers (DAPI) was purchased from Ciba-Geigy Corp. The acetylene terminated imide oligomer powder (Thermid MC-600) derived from BTDA, aminophenylacetylene, and 1,3-bis (2-aminophenoxy) benzene (APB) was obtained from National Starch and Chemical Company. Kapton Type II (PMDA-ODA) films were obtained from DuPont Co., Apical polyimide films were obtained from Allied Corp., and Upilex Type-S and Type-R polyimide films derived from 3,3, 4,4 -biphenyl tetracarboxylic dianhydride (BPDA) plus p-phenylenediamine (PDA) and ODA, respectively were obtained from ICI Americas Inc. 

Sulfonated polyimides (sPI) are another type of ionomers that have been prepared [5] by copolymerization of 4,4 -diamino-biphenyl 2,2 -disulphonic acid (BDSA), 4,4 -oxydianiline (ODA), and naphtalenic or phthalic anhydrides. Polyimide structures based on six-membered rings derived from naphtalenics anhydrides, such as 1,4,5,8-naphtalene tetracarboxylic dianhydride (NTDA), shown in Fig. 6.8, are more hydrolitically stable than the five-membered rings basedoxy-diphthalic anhydrides (ODPA). 

Neither polyimides derived from 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA) nor from biphenyl tetracarboxylic anhydride with aliphatic spacers have yielded a liquid crystalline phase. The need for an extraring to obtain meso-genic properties was evident. Inoue et al. reported the existence of mesophase in a series of polyimides synthesized from the nylon-salt-type terphenyl tetracarboxylic anhydride with aliphatic diamines (Structure 4) [53-55]. 

The acetylenic biphenyl moiety was incorporated into the polymer backbone of two aromatic heterocyclic systems, the polyphenylquinoxaline and aromatic polyimide. The introduction was carried out via the amino monomers, 2,2 -bis(phenylethynyl)-U,U, 5,5 -tetraminobiphenyl and 2,2 -bis(phenylethynyl)-5,5 -diaminobiphenyl. The IMG type of reaction depends only upon a rotational movement of the polymer backbone which requires substantially less molecular mobility than the translational movement needed for the intermolecular cure. Therefore, the curing reaction can continue to completion long after the resin is essentially vitrified, and the resultant use temperature should be substantially higher than the cure temperature. 

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