Molecular weight and concentration effects on gel/sol transitions in a segmented rigid-rod polyimide solution

✍ Scribed by Sung Koo Lee; Stephen Z. D. Cheng; Zongquan Wu; Chul Joo Lee; Frank W. Harris; Thein Kyu; Jen-Chang Yang

• Book ID: 104528482
• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 853 KB
• Volume: 30
• Category: Article
• ISSN: 0959-8103
• DOI: 10.1002/pi.4990300117

✦ Synopsis

Abstract

Gel/sol and order/disorder transitions can be observed in a segmented rigid‐rod polyimide solution at different concentrations and molecular weights. This polyimide was synthesized from 3,3′,4,4′‐biphenyltetracarboxylic dianhydride and 2,2′‐bis(trifluoromethyl)‐4,4′‐diaminobiphenyl in refluxing 3‐cresol in a one‐step process. Above about 140°C, the polymers are completely soluble in 3‐cresol in a concentration range up to 12(w/w)%. During cooling, the hot solutions undergo a mechanical sol/gel transition to form thermally reversible gels. In the gel state, an ordered structure develops. Both the gel/sol and order/disorder transitions are dependent upon concentration, temperature, and molecular weight, but the two transitions exhibit different kinetics. Possible mechanisms of these transitions are discussed.