Solution properties of polyamic acids and their amine salts

✍ Scribed by Yasunari Maekawa; Takao Miwa; Kazuyuki Horie; Takashi Yamashita

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 276 KB
• Volume: 30
• Category: Article
• ISSN: 1381-5148
• DOI: 10.1016/1381-5148(95)00129-8

✦ Synopsis

Solution properties such as viscosity, critical concentration, radius of gyration, and activation energy in aqueous solutions are described for [BPDA/PDA]polyamic acid (PAA) and their salts with various amines (PAS). Although PAA and their salts with BujN, HexxN, Oct3N, and pyridine, were insoluble in H20, only the salt with Et3N (PAS(EtXN)) was soluble in H20. The different solubility of PAS suggests that higher base strength as well as shorter alkyl length of amines enhance water solubility of PAS. PAS(EtjN) showed critical concentrations at 18, 14, and 7.8 wt% in NMP, NMP/H20 (l/l), and H20, respectively. The radius of gyration, which is calculated from the critical concentration, in Hz0 is 1.3 times larger than that in NMP; that is, the polymer chain expands in Hz0 rather than in NMP. PAS(Et,N) in Hz0 showed larger activation energy of viscosity than that in NMP. However, PAA and PAS(Et,N) showed similar activation energies in the NMP solution. Therefore, it is concluded that the amine salts of the polyamic acids are hydrated by several water molecules in H20, resulting in the larger radius of gyration and lager activation energies.