Summary: A novel experimental approach, that is, two‐dimensional (2D) correlation analysis based on time‐resolved attenuated total reflection (ATR) FT‐IR spectroscopy, has been used to study the diffusion behavior of ethylene glycol molecules into EP and EPB (novolac epoxy resins cured with novolac resin or novolac butyrate resin, respectively). The diffusion behavior of ethylene glycol into these systems is discussed and compared with that of water. Ethylene glycol absorbed in EP can be classified into two types (free and bound types), while in EPB a third type (referred to as “specific” type) is also observed, which differs from water sorption behavior. In particular, it is interesting to find that the hydrogen bonding of specific ethylene glycol involves two hydroxyl groups rather than one hydroxyl group and polar group in epoxy networks (carbonyl group), a similar example of which has not been previously observed. In addition, in both EP and EPB, bound ethylene glycol molecules diffuse faster than any other types.
Asynchronous 2D correlation spectra of ethylene glycol in the two resins studied here. Positive peaks are unshaded, whereas negative peaks are shaded.
