Determination of molecular weight averages and molecular weight distribution by g.p.c. of N-trifluoroacetylated polyamides

To determine their molecular weight averages and molecular weight distribution, N-trifluoroacetylated (TFA) polyamides are studied using gel permeation chromatography in tetrahydrofuran at 25°C. Several calibration methods (calibration with polydisperse standards, universal calibration) are tested; among these, direct calibration of M_w of polydisperse samples vs. peak maximum of the corresponding g.p.c. chromatogram leads to the best results. Calculated molecular weight averages of nylon 6-TFA and Trogamid^R-TFA are compared with data from light scattering, viscometry and osmometry.