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N ‐methylation of wholly aromatic polyamides for size‐exclusion chromatography
Author(s) -
Mourey T. H.,
Guistina R. A.,
Bryan T. G.,
Thornbury R. F.,
Blevins R.,
Perry R. J.,
Turner S. R.
Publication year - 1992
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1992.070451113
Subject(s) - size exclusion chromatography , gel permeation chromatography , polyamide , chemistry , dimethylformamide , intrinsic viscosity , polymer , polymer chemistry , sulfuric acid , molar mass distribution , reagent , aramid , viscometer , column chromatography , amide , organic chemistry , chromatography , viscosity , materials science , solvent , fiber , composite material , enzyme
Wholly aromatic polyamides, including poly(1,4‐phenyleneisophthalamide) and poly(1,4‐phenyleneterephthalamide) are N ‐methylated to render them soluble in N,N ‐dimethylformamide, a common size‐exclusion chromatography eluent. The procedure N ‐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 the N ‐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. Examples are given.