N-alkylation and Hofmann elimination from thermal decomposition of R4N+ salts of aromatic polyamide polyanions : synthesis and stereochemistry of N-alkylated aromatic polyamides

The reaction of poly(p-phenyleneterephthalamide) (PPTA) with (n-Bu) 4 N + −OH or Et 4 N + −OH gives dimethyl sulfoxide (DMSO) soluble polyanions from deprotonation of the amide hydrogen. The n(R 4 N + ) PPTA n− salts thermally decompose by Hofmann elimination to yield neutral PPTA, olefin, and NR 3 . Dissolving PPTA by deprotonation and thermally decomposing the R 4 N + salt can be used to process the polymer. Films cast from DMSO solutions of nR 4 N + PPTA n− convert from polyanion to a PPTA film when heated to about 200 o C, removing solvent and volatile by products, and leaving a crisp PPTA film. Model studies show that N-alkylation competes with the Hofmann elimination of nR 4 N + PPTA n−