Abstract
The origin of the gel formation during the conversion of poly(amic acid)s to polyisoimides, and methods for its prevention are described. The gelation behaviour was studied as a function of the cyclodehydration temperature, the concentration and end-groups of 4,4′-oxydianiline/4,4′-oxydiphthalic anhydride poly(amic acid) systems, using 1,3-dicyclohexylcarbodiimide as a dehydrating agent. The 1H NMR spectroscopic data showed that gel formation during polyisoimide synthesis results from the amide formation reaction of terminal amine groups with acylated poly(amic acid)s. Dilution of poly(amic acid) solutions and lowering cyclodehydration temperatures retarded gelation. However, complete prevention of gel formation at relatively high concentration (15%) and temperature (20°C) was achieved only for phthalic anhydride end-capped polyamic systems.
| Original language | English |
|---|---|
| Pages (from-to) | 8-10 |
| Number of pages | 3 |
| Journal | Polymer International |
| Volume | 49 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 2000 |
Keywords
- Gelation
- Poly(amic acid)
- Polyimide
- Polyisoimide