A methof for molecular weight determination of polyether polyols has been developed using 1H-NMR analysis of ester-H groups (-COOCH2-). Polyethylene glyol (PEG) is esterified directly in the sample tube. Then
the number average molecular weight of PEG can be calculated by measuring the ratio of 1H-NMR absorptions of mo-nomeric units ((CH2CH2O)n-1) in the polymeric structure to those of ester-H. This method is simple and time-saving. It excludes the effect of trace water on molecular weight determination. The quantitative resultsobtained by above-mentioned method could be satisfactory.