AbstractWholly aromatic polyamides, including poly(1,4‐phenyleneisophthalamide) and poly(1,4‐phenyleneterephthalamide) areN‐methylated to render them soluble inN,N‐dimethylformamide, a common size‐exclusion chromatography eluent. The procedureN‐methylates 50–55 of the total amide linkages in these two examples, permitting reproducible measurement of their absolute molecular weight distributions using differential viscometry detection. There is no observable degradation in molecular weight resulting from theN‐methylation, provided the excess methylating reagent is destroyed shortly after completion of the derivatization by quenching with potassium acetate. The validity of the molecular weight data obtained by the method is confirmed by light‐scattering measurements on derivatized polymer and by comparison to the molecular weight of underivatized polymer that can be approximated from the intrinsic viscosity in concentrated sulfuric acid. The method is applicable to a variety of wholly aromatic polyamide structures. E
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