Relaxation processes and molecular motion in a new semicrystalline polyimide

✍ Scribed by Stephen Z. D. Cheng; Tammy M. Chalmers; Yi Gu; Yeocheol Yoon; Frank W. Harris; Jinlong Cheng; Matilda Fone; Jack L. Koenig

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 637 KB
• Volume: 196
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.1995.021960507

✦ Synopsis

A new polyimide was synthesized from 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 2,2-dimethyl-l,3-(4-aminophenoxy)propane (DMDA), and abbreviated to be BTDA-DMDA. This polymer possesses three relaxation processes which have been observed through dynamic mechanical and dielectric analyses above -150°C. The a relaxation process has been assigned to be the glass transition and occurs at about 250 "C with an apparent activation energy of 420 kJ/mol. Two subglass relaxation processes are aprelaxation process at around 100-170 "C in a frequency range from 0,l Hz to 100 kHz with an activation energy of 182 kJ/mol and a y relaxation process occurs at around -80 "C with an activation energy of 44 kJ/mol. Carbon-13 solid state nuclear magnetic resonance experiments were carried out for the study of molecular dynamics at different temperatures. The results indicate that the y relaxation is responsible for an oscillation and R flipping motion of the two phenoxy rings in the DMDA portion. Theprelaxation was shown to pertain to the kHz-motion of the aromatic imide rings in the BTDA portion. The molecular motion of the DMDA and BTDA portions are largely decoupled from each other in the frequency region studied.