EFFECTS OF ADDITION OF AN ELECTROLYTE ON SIZE-EXCLUSION CHROMATOGRAPHY OF POLYAMIDES USING HEXAFLUORO-2-PROPANOL AS MOBILE-PHASE

Polyelectrolyte effects for polyamides and poly(methyl methacrylate) (PMMA) used as calibration standards and the suppression of these effects by the addition of sodium trifluoroacetate to the mobile phase were shown and discussed. The addition of the electrolyte helped to the disaggregation of the polymer samples by breaking down hydrogen bonding. Besides the disaggregation of the polymer samples, the addition of the electrolyte caused the change of the retention volume and peak width of PMMA. Elution of PMMA having higher molecular weight than 6 x 10(4) was retarded and that having smaller one than 6 x 10(4) was hastened by the addition of the electrolyte. Peak width of PMMA became also narrower in about 20%. PMMA equivalent molecular weights of polyamides were plotted against real molecular weights of the polyamides measured by end group analysis and next equations were obtained. log M(nylon 6) = -1.53402 + 1.352 log M(PMMA eq) log M(nylon 6,6) = -4.88506 + 2.143 log M(PMMA eq)