Investigations of the chemical structure of sulfonated amino‐formaldehyde resins. II. Size exclusion chromatography of sulfonated urea‐formaldehyde resins

The liquid chromatographic behavior of sulfonated urea‐formaldehyde resins in aqueous eluents was investigated and a suitable molecular weight calibration was established at a column system, consisting of μ‐PORASIL 60 Å and μ‐BONDAGEL (linear). It was demonstrated, that in deionized water electrostatic interactions between the stationary phase and the resin molecules occurred and the separation according to size exclusion mechanism was disturbed. Ion exclusion was successfully eliminated, using aqueous sodium sulfate solution as the mobile phase. The molecular weight of the sulfonated urea‐formaldehyde resins was shown to be influenced by the ratio of the resin components. Increasing the formaldehyde to urea ratio resulted in an increase in the resin's molecular weight, whereas increasing the sulfite to urea ratio led to a decrease in the molecular weights. An explanation of this observation was presented.