| abstract |
Sulfonated polyimides and polyamic acids, particularly polyetherimides, are prepared by reacting the unsulfonated polymer with a mild sulfonating agent. Illustrative sulfonating agents are the complexes of sulfur trioxide and trialkyl or triaryl phosphates, especially the sulfur trioxide-triethyl phosphate complex having a molar ratio of sulfur trioxide to triethyl phosphate of 2:1. |