¹³ C NMR Quantification of Isomers Differing in PEG Chain Length Combination in Bisphenol-A Ethoxylate Diacrylate Oligomers

We directly quantified bisphenol A ethoxylate diacrylate (BEDA) isomers with molecular weights up to approximately 1000 by 13 C NMR spectroscopy without prior separation. BEDA is a complex mixture of oligomers, comprising homologues that differ in the sum of the degrees of polymerization (SDP) of the two poly(ethylene glycol) (PEG) chains, each of which, in turn, consists of isomers with different combinations of PEG chain lengths for the same SDP. Although isomers with SDPs of 4 and 5 have been quantified by gas chromatography, the separation of the isomers by liquid chromatography has not been reported, owing to numerous species and their similar physicochemical properties. 13 C NMR spectra of BEDAs with average SDPs of 3, 4, and 10 were acquired in toluene- d 8 at a digital resolution of 0.1 Hz/point. The signal of quaternary aromatic carbon attached to the isopropylidene group in the 143 ppm region was resolved depending on the specific PEG chain length combination, revealing over 50 distinct signals for the BEDA with an average SDP of 10. Signals were assigned on the basis of the additivity of chemical shifts and the relative signal intensities, which varied with the degree of polymerization. Spectral deconvolution of this 143 ppm region for the average SDP 10 sample enabled the quantification of 39 individual molecular species with SDPs of up to 16. This NMR method extends the quantifiable range for BEDA isomers by approximately 10 ethylene oxide units beyond that of conventional gas chromatography.